EP0000315B1 - Process for preparing optically active citronellal - Google Patents

Process for preparing optically active citronellal Download PDF

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Publication number
EP0000315B1
EP0000315B1 EP78420001A EP78420001A EP0000315B1 EP 0000315 B1 EP0000315 B1 EP 0000315B1 EP 78420001 A EP78420001 A EP 78420001A EP 78420001 A EP78420001 A EP 78420001A EP 0000315 B1 EP0000315 B1 EP 0000315B1
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Prior art keywords
rhodium
process according
chiral
bis
carbon atoms
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German (de)
French (fr)
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EP0000315A1 (en
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Paul Aviron-Violet
Tuan-Phat Dang
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Rhone Poulenc Recherches SA
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Rhone Poulenc Industries SA
Rhone Poulenc Recherches SA
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B01J31/2404—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/18—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms
    • B01J31/1845—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes containing nitrogen, phosphorus, arsenic or antimony as complexing atoms, e.g. in pyridine ligands, or in resonance therewith, e.g. in isocyanide ligands C=N-R or as complexed central atoms the ligands containing phosphorus
    • B01J31/1875—Phosphinites (R2P(OR), their isomeric phosphine oxides (R3P=O) and RO-substitution derivatives thereof)
    • B01J31/188—Amide derivatives thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B01J31/2404—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring
    • B01J31/2409—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring with more than one complexing phosphine-P atom
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B01J31/2404—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring
    • B01J31/2409—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring with more than one complexing phosphine-P atom
    • B01J31/2414—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring with more than one complexing phosphine-P atom comprising aliphatic or saturated rings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/24—Phosphines, i.e. phosphorus bonded to only carbon atoms, or to both carbon and hydrogen atoms, including e.g. sp2-hybridised phosphorus compounds such as phosphabenzene, phosphole or anionic phospholide ligands
    • B01J31/2404—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring
    • B01J31/2442—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring comprising condensed ring systems
    • B01J31/2447—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring comprising condensed ring systems and phosphine-P atoms as substituents on a ring of the condensed system or on a further attached ring
    • B01J31/2452—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring comprising condensed ring systems and phosphine-P atoms as substituents on a ring of the condensed system or on a further attached ring with more than one complexing phosphine-P atom
    • B01J31/2457—Cyclic ligands, including e.g. non-condensed polycyclic ligands, the phosphine-P atom being a ring member or a substituent on the ring comprising condensed ring systems and phosphine-P atoms as substituents on a ring of the condensed system or on a further attached ring with more than one complexing phosphine-P atom comprising aliphatic or saturated rings, e.g. Xantphos
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/61—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups
    • C07C45/62—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by reactions not involving the formation of >C = O groups by hydrogenation of carbon-to-carbon double or triple bonds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2231/00—Catalytic reactions performed with catalysts classified in B01J31/00
    • B01J2231/60—Reduction reactions, e.g. hydrogenation
    • B01J2231/64—Reductions in general of organic substrates, e.g. hydride reductions or hydrogenations
    • B01J2231/641—Hydrogenation of organic substrates, i.e. H2 or H-transfer hydrogenations, e.g. Fischer-Tropsch processes
    • B01J2231/645—Hydrogenation of organic substrates, i.e. H2 or H-transfer hydrogenations, e.g. Fischer-Tropsch processes of C=C or C-C triple bonds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2531/00—Additional information regarding catalytic systems classified in B01J31/00
    • B01J2531/80—Complexes comprising metals of Group VIII as the central metal
    • B01J2531/82—Metals of the platinum group
    • B01J2531/822—Rhodium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/16—Catalysts comprising hydrides, coordination complexes or organic compounds containing coordination complexes
    • B01J31/20—Carbonyls

Definitions

  • the subject of the present invention is a process for the preparation of optically active citronellal, also called chiral citronellal, by asymmetric hydrogenation of the mineral (E-dimethyl-3,7 octadiene-2,6 al) or geranial (Z-dimethyl-3.7 octadiene -2.6 al) achiral isomers constituting the citral.
  • the chiral citronellal is a suitable intermediary in organic synthesis; in particular d-citronellal is used for the preparation of (-) (1S) menthol designated below 1-menthol, by a process which implements the cyclization of d-citronellal in (-) (1 S) -isopulégol under the influence of a proton catalyst or thermally, then the hydrogenation of isopulegol to (D-menthoi (cf. JC LEFFINGWELL and RE SHACKELFORD, Cosmetics and Perfumery 89 70-78 / 1974 /).
  • the d-citronellal used for the synthesis of 1-menthol is obtained from various natural essences containing mainly d-citronellal and in particular from the essence of citronella.
  • the use of chiral citronellal of natural origin is not entirely satisfactory insofar as, due to the fluctuation of the prices of natural products, it happens periodically that the price of d-citronellal is higher than that of natural menthol . It is therefore important for the industry to have a source of chiral citronellal having a relatively stable prices and leading to a synthetic 1-menthol which D rices of returns is less than that of natural menthol.
  • 3,849,480 a process for the hydrogenation of ethylenically unsaturated compounds such as ⁇ -phenylacrylic acid, 3-methyl-2-cyclohexene one and methyl acid -2 butene-2 oic, but none of these compounds has a double ethylenic unsaturation linked to two asymmetric carbon atoms so that in these cases there is no risk of isomer formation.
  • the prior art has taught various types of catalysts which may be suitable for carrying out asymmetric syntheses.
  • 2,161,200 describes rhodium complexes with optically active ligands particular from the group of diphosphines, diarsines or distibines and teaches their use in synthesis. asymmetric, in particular for the hydrogenation of ⁇ -acetylaminocinnamic acid to acetylalanine.
  • hitherto it has never been proposed to prepare the chiral citronellal by asymmetric hydrogenation of the citral.
  • the achiral synthetic citronellal obtained by hydrogenation of the citral could constitute an interesting source of chiral citronellal and in particular of d-citronellal, however there is no industrial process for splitting the racemic citronellal into its enantiomers, so that the industry has no process for obtaining chiral citronellals synthetically.
  • the present invention aims precisely to solve such a problem.
  • the subject of the present invention is a process for the preparation of optically active citronellal, characterized in that the neral or geranial is hydrogenated in the presence of a catalyst consisting of a complex soluble in the reaction medium formed from a derived from rhodium and a chiral phosphine.
  • chiral phosphine denotes a phosphine or diphosphine in which at least one of the organic residues linked to the phosphorus atom comprises at least one chiral carbon atom, and / or in which at least one of the phosphorus atoms is chiral.
  • the soluble complex of the rhodium derivative and of the chiral phosphine can be prepared extemporaneously or be formed "in situ" under the conditions of the reaction by using the constituents of the complex. This latter method which has the advantage of simplicity is generally preferred.
  • rhodium derivatives suitable for carrying out the process according to the invention comprising residues of various kinds. They can be rhodium salts of mineral or organic acids or rhodium complexes whose ligands can be replaced by chiral phosphine.
  • rhodium halides such as hydrated rhodium trichloride
  • olefins of general formula: in which X represents a halogen atom: chlorine or bromine for example, x is an integer from 1 to 4 and L an aliphatic or cycloaliphatic olefin or diolefin such as ethylene, propylene, butene, isobutene , butadiene, 1,5-hexadiene, 1,4-heptadiene, 1,5-octadiene, isoprene, cyclohexadiene-1,3, cyclooctadiene-1,5; as examples of such complexes may be cited the ⁇ , ⁇ 'dichloro bis- (cyclohexadiene-1,3-rhodium), the ⁇ , ⁇ '-dichloro bis- (cydooctadiene-1
  • L 1 is triphenylphosphine.
  • rhodium derivatives use is preferably made of the various rhodiumcarbonyls and in particular tetrarhodium dodecacarbonyl and hexarhodiumhexadecacarbonyl. Rhodium complexes taken in cationic form can also be used.
  • alkylene radicals mention may be made of methylene, ethylene, propylene and 2-ethylpropylene radicals;
  • A can also represent a cyclobutylene radical; 1,4-cyclohexylene; 2-methyl-1,4-cyclohexylene; an ortho- or p-phenylene radical; a 2,3-dimethoxy-1,4-butylene radical.
  • divalent chiral radicals A formed by a chain of alkylene and cycloalkylene or heterocyclic or polycyclic or amino radicals mention may be made of those of formulas:
  • chiral diphosphines which can be used in the process according to the invention, there may be mentioned, without implying any limitation: bis (diphenylphosphinomethyl) -1,2-cyclobutane (DPCB), bis (dimethylphophinomethyl) -1,2 cyclobutane , bis (di-n-butylphosphinomethyl) -1,2 cyclobutane, bis (dioctylphosphinomethyl -) - 1,2 cyclobutane, bis (ditolylphosphinomethyl-1,2 cyclobutane, bis (dinaphthylphosphinomethyl) -1,2 cyclobutane bis (ethyl, hexylphosphinomethyl) -1.2 cyclobutane, bisldiphenylphosphinomethyl) -1.2 cyclopentane; bis (diphenylphosphinomethyl) -1.2 cyclohex
  • DDB 2,3-dimethoxy butane
  • tetramenthyldiphosphine bis (N, N'-diphenylphosphino) bis (N, N '(1-phenylethyl)) diaza-1,4 butane.
  • phosphines mentioned above use is preferably made of bis (diarylphosphino-methyl) -1,2 cyclobutanes described in French patent No. 73/18 319.
  • phosphines with chiral phosphorus atoms mention may be made of methyl cyclohexyl orthomethoxyphenyl phosphine; methylcyclohexylphenylphosphine; benzylphenylmethylphosphine.
  • the amount of rhodium derivative used in the process of the invention expressed in gram atoms of metal per mole of diene aldehyde to be hydrogenated can vary within wide limits. Whether it is the preformed complex or the derivative capable of generating this complex under the conditions of the reaction, the quantity can be chosen so that the number of gram atoms of rhodium per mole of aldehyde is between 1 ⁇ 10 - 4 and 1 ⁇ 10 -1 .
  • the amount of phosphine involved in the process depends on the nature of the phosphine and that of the rhodium derivative. This quantity, expressed by the number of gram atoms of phophore per gram atom of rhodium is such that this ratio can vary between 0.5 and 10; preferably the P / Rh ratio is between 1 and 6. However, P / Rh ratios greater than 10 could be used without departing from the scope of the present invention, but this would not provide any particular advantage.
  • the temperature at which the hydrogenation is carried out is not critical and can vary within wide limits. In general it is between 0 and 150 ° C and preferably between 10 and 100 ° C. It is the same for the hydrogen pressure which can vary between 0.1 and 100 bars and preferably between 0.5 and 50 bars.
  • the asymmetric hydrogenation of the mineral or geranial is preferably carried out in an inert solvent of the aldehyde and the catalyst.
  • solvents that may be mentioned include hydrocarbons (hexane, heptane, cyclohexane, benzene, toluene), alcohols (methanol, ethanol), nitriles (acetonitrile, benzonitrile).
  • optical purity P.0 will denote the ratio of the rotary power ( ⁇ 1 ) D of the product obtained by the process to the rotary power ( ⁇ ) D of the product measured under the same conditions, multiplied by 100, ie
  • optical yield is meant the value of the optical purity of the product which would be obtained by using an optically pure phosphine.
  • the apparatus is purged with hydrogen and then the contents of the flask are kept under 1 bar of hydrogen for 4 hours at 25 ° C.
  • the reaction is stopped and the reaction mass is subjected to a gas chromatographic analysis: the geranial transformation rate is 100% and the citronellal yield 99%.
  • the rotary power of pure 1-citronellal ( ⁇ ) 25 D measured on a solution at 6 g / 100 cm 3 in cyclohexane is -15.6 °.
  • the PO of the product obtained is 56%.
  • the reaction time is 10 hours
  • Example 2 The procedure is as in Example 1, replacing the (+) - DPCB with the (+) - DIOP.
  • the geranial / Rh ratio is 120 and a P / Rh ratio of 4 and 6 is used successively.
  • the procedure is as in Example 1, replacing the (+) - DPCB with the (-) - DPCB.
  • the ratio of the number of moles of geranial (G) to the number of gram atoms of rhodium (G / Rh) is equal to 123 and the ratio P / Rh to 4.
  • the (-) - DPCB has an optical purity of 95 , 5%.
  • the reaction time is 18 hours, the geranial transformation rate of 99%, the RT into citronellal of 99%.
  • the mineral used contained 7% geranial.

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  • Engineering & Computer Science (AREA)
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Description

La présente invention a pour objet un procède de préparation de citronellal optiquement actif, encore dénommé citronellal chiral, par hydrogénation asymétrique du néral (E-diméthyl-3,7 octadiène-2,6 al) ou du géranial (Z-diméthyl-3.7 octadiène-2,6 al) isomères achiraux constitutifs du citral.The subject of the present invention is a process for the preparation of optically active citronellal, also called chiral citronellal, by asymmetric hydrogenation of the mineral (E-dimethyl-3,7 octadiene-2,6 al) or geranial (Z-dimethyl-3.7 octadiene -2.6 al) achiral isomers constituting the citral.

Le citronellal chiral est un intermédiaire apprécié en synthèse organique; en particulier le d-citronellal est utilisé pour la préparation du (-) (1S) menthol désigné ci-après 1-menthol, par un procédé qui met en oeuvre la cyclisation du d-citronellal en (-) (1 S)-isopulégol sous l'influence d'un catalyseur protonique ou par voie thermique, puis l'hydrogénation de l'isopulégol en (D-menthoi (cf. J.C. LEFFINGWELL et R.E. SHACKELFORD, Cosmetics and Perfumery 89 70-78/1974/).The chiral citronellal is a suitable intermediary in organic synthesis; in particular d-citronellal is used for the preparation of (-) (1S) menthol designated below 1-menthol, by a process which implements the cyclization of d-citronellal in (-) (1 S) -isopulégol under the influence of a proton catalyst or thermally, then the hydrogenation of isopulegol to (D-menthoi (cf. JC LEFFINGWELL and RE SHACKELFORD, Cosmetics and Perfumery 89 70-78 / 1974 /).

Le d-citronellal utilisé pour la synthèse du 1-menthol est obtenu à partir de diverses essences naturelles contenant principalement du d-citronellal et en particulier à partir de l'essence de citronelle. L'emploi de citronellal chiral d'origine naturelle n'est pas entièrement satisfaisant dans la mesure où, en raison de la fluctuation des prix des produits naturels, il arrive périodiquement que le prix du d-citronellal soit plus élevé que celui du menthol naturel. Il importe donc à l'industrie de disposer d'une source de citronellal chiral ayant un prix relativement stable et conduisant à un 1-menthol synthétique dont le Drix de revient soit inférieur à celui du menthol naturel.The d-citronellal used for the synthesis of 1-menthol is obtained from various natural essences containing mainly d-citronellal and in particular from the essence of citronella. The use of chiral citronellal of natural origin is not entirely satisfactory insofar as, due to the fluctuation of the prices of natural products, it happens periodically that the price of d-citronellal is higher than that of natural menthol . It is therefore important for the industry to have a source of chiral citronellal having a relatively stable prices and leading to a synthetic 1-menthol which D rices of returns is less than that of natural menthol.

Il existe divers procédés d'hydrogénation du citral en citronellal racémique. Ainsi dans la demande de brevet français No 75-19.070, publiée sous le No 2.314.911, on a décrit un procédé d'hydrogénation sélective en phase hétérogène du citral en citronellal en présence d'un catalyseur au palladium métallique déposé sur un support inerte et d'un agent alcalin (hydroxyde alcalin ou alcalino- terreux) en milieu hydroalcoolique. Bien que ce procédé permette une hydrogénation sélective de la double liaison en α du groupe carbonyle, il ne peut conduire à l'obtention de citronellal optiquement actif.There are various methods of hydrogenating citral to racemic citronellal. Thus in French patent application No 75-19.070, published under No 2.314.911, a process has been described for the selective hydrogenation in heterogeneous phase of citral to citronellal in the presence of a metallic palladium catalyst deposited on an inert support. and an alkaline agent (alkali or alkaline earth hydroxide) in an aqueous-alcoholic medium. Although this process allows selective hydrogenation of the α double bond of the carbonyl group, it cannot lead to the production of optically active citronellal.

On connaît divers complexes achiraux du rhodium avec des ligands du type des trialcoyl- ou triarylphosphines et leur emploi comme catalyseurs d'hydrofromylation des oléfines et d'hydroaldo- lisation des aldéhydes (cf. brevet américain No 3.939.188). On a bien proposé dans le brevet des Etats-Unis d'Amérique No 3.849.480 un procédé d'hydrogénation de composés à insaturation éthyléniques tels que l'acide a-phénylacrylique, la méthyl-3 cyclohexène-2 one et l'acide méthyl-2 butène-2 oïque, mais aucun de ces composés ne comporte une double insaturation éthylénique liée à deux atomes de carbone asymétriques de sorte que dans ces cas là, il n'y a pas de risque de formation d'isomères. L'art antérieur a enseigné divers types de catalyseurs pouvant convenir à la réalisation de synthèses asymétriques. C'est ainsi qu'outre le brevet américain No 3.849.480 précité, la demande allemande No 2.161.200 décrit des complexes du rhodium avec des ligands optiquement actifs particuliers du groupe des diphosphines, des diarsines ou des distibines et enseigne leur emploi en synthèse asymétrique, en particulier pour l'hydrogénation de l'acide a-acétylaminocinnamique en acétylalanine. Cependant jusqu'ici il n'a jamais été proposé de préparer le citronellal chiral par hydrogénation asymétrique du citral.Various achiral complexes of rhodium are known with ligands of the trialkyl- or triarylphosphine type and their use as catalysts for hydrofromylation of olefins and hydroaldolization of aldehydes (cf. US Pat. No. 3,939,188). It has indeed been proposed in United States patent No. 3,849,480 a process for the hydrogenation of ethylenically unsaturated compounds such as α-phenylacrylic acid, 3-methyl-2-cyclohexene one and methyl acid -2 butene-2 oic, but none of these compounds has a double ethylenic unsaturation linked to two asymmetric carbon atoms so that in these cases there is no risk of isomer formation. The prior art has taught various types of catalysts which may be suitable for carrying out asymmetric syntheses. Thus, in addition to the aforementioned American patent No. 3,849,480, the German application No. 2,161,200 describes rhodium complexes with optically active ligands particular from the group of diphosphines, diarsines or distibines and teaches their use in synthesis. asymmetric, in particular for the hydrogenation of α-acetylaminocinnamic acid to acetylalanine. However, hitherto it has never been proposed to prepare the chiral citronellal by asymmetric hydrogenation of the citral.

Le citronellal synthétique achiral obtenu par hydrogénation du citral (mélange de néral et de géranial) pourrait constituer une source intéressante de citronellal chiral et notamment de d-citronellal, toutefois il n'existe pas de procédé industriel de dédoublement du citronellal racémique en ses énantioméres, de sorte que l'industrie ne dispose d'aucun procédé permettant d'obtenir des citronellals chiraux par voie synthétique. La présente invention se propose précisément de résoudre un tel problème.The achiral synthetic citronellal obtained by hydrogenation of the citral (mixture of neral and geranial) could constitute an interesting source of chiral citronellal and in particular of d-citronellal, however there is no industrial process for splitting the racemic citronellal into its enantiomers, so that the industry has no process for obtaining chiral citronellals synthetically. The present invention aims precisely to solve such a problem.

Plus particulièrement la présente invention a pour objet un procédé de préparation de citronellal optiquement actif caractérisé en ce que l'on hydrogène le néral ou le géranial en présence d'un catalyseur constitué par un complexe soluble dans le milieu réactionnel formé à partir d'un dérivé du rhodium et d'une phosphine chirale.More particularly, the subject of the present invention is a process for the preparation of optically active citronellal, characterized in that the neral or geranial is hydrogenated in the presence of a catalyst consisting of a complex soluble in the reaction medium formed from a derived from rhodium and a chiral phosphine.

Par phosphine chirale on désigne une phosphine ou diphosphine dont l'un au moins des restes organiques liés à l'atome de phosphore comporte au moins un atome de carbone chiral, et/ou dont un au moins des atomes de phosphore est chiral.The term “chiral phosphine” denotes a phosphine or diphosphine in which at least one of the organic residues linked to the phosphorus atom comprises at least one chiral carbon atom, and / or in which at least one of the phosphorus atoms is chiral.

Le complexe soluble du dérivé du rhodium et de la phosphine chirale peut être préparé extemporanément ou être formé "in situ" dans les conditions de la réaction par mise en oeuvre des constituants du complexe. Cette dernière façon de faire qui a l'avantage de la simplicité est généralement préférée.The soluble complex of the rhodium derivative and of the chiral phosphine can be prepared extemporaneously or be formed "in situ" under the conditions of the reaction by using the constituents of the complex. This latter method which has the advantage of simplicity is generally preferred.

Comme dérivés du rhodium convenant à la mise en oeuvre du procédé selon l'invention on utilise des dérivés du rhodium comportant des restes de nature diverses. Il peut s'agir de sels de rhodium d'acides minéraux ou organiques ou de complexes du rhodium dont les ligands peuvent être remplacés par la phosphine chirale. On peut par exemple faire appel à des halogénures de rhodium tel que le trichlorure de rhodium hydraté; à des complexes du rhodium avec les oléfines de formule générale:

Figure imgb0001
dans laquelle X représente un atome d'halogène: chlore ou brome par exemple, x est un nombre entier de 1 à 4 et L une oléfine ou une dioléfine aliphatique ou cycloaliphatique telle que l'éthylène, le propylène, le butène, l'isobutène, le butadiène, l'hexadiène-1,5, l'heptadiène-1,4, l'octadiène-1,5, l'isoprène le cyclohexadiène-1,3,le cyclooctadiene-1,5; comme exemples de tels complexes ont peut citer le µ, µ' dichloro bis-(cyclohexadiène-1,3-rhodium), le µ, µ'-dichloro bis-(cydooctadiène-1,5 rhodium), le µ, µ'-chloro bis(diethylène rhodium)); on peut encore faire appel à des complexes rhodium carbonyle et à leurs dérivés tels que ceux répondant à la formule générale:
Figure imgb0002
dans laquelle L, représente un ligand mono- ou polydentate et notamment une phophine achirale de formule générale:
Figure imgb0003
dans laquelle R représente un radical achiral alcoyle, cycloalcoyle aryle ayanat de 1 à 10 atomes de carbone tel que les radicaux méthyle, éthyle, propyle, butyles, pentyles, hexyles, octyles, cyclohexyle, phényle, toluyle. De préférence L1 est la triphénylphosphine. Parmi les dérivés du rhodium précités on fait appel de préférence aux divers rhodiumcarbonyle et notamment au tétrarhodium dodécacarbonyle et à l'hexarhodiumhexadécacarbonyle. Les complexes du rhodium pris sous forme cationique peuvent également être utilisés.As rhodium derivatives suitable for carrying out the process according to the invention, rhodium derivatives are used comprising residues of various kinds. They can be rhodium salts of mineral or organic acids or rhodium complexes whose ligands can be replaced by chiral phosphine. It is possible, for example, to use rhodium halides such as hydrated rhodium trichloride; to rhodium complexes with olefins of general formula:
Figure imgb0001
 in which X represents a halogen atom: chlorine or bromine for example, x is an integer from 1 to 4 and L an aliphatic or cycloaliphatic olefin or diolefin such as ethylene, propylene, butene, isobutene , butadiene, 1,5-hexadiene, 1,4-heptadiene, 1,5-octadiene, isoprene, cyclohexadiene-1,3, cyclooctadiene-1,5; as examples of such complexes may be cited the µ, µ 'dichloro bis- (cyclohexadiene-1,3-rhodium), the µ, µ'-dichloro bis- (cydooctadiene-1,5 rhodium), the µ, µ'- chloro bis (diethylene rhodium)); it is also possible to use rhodium carbonyl complexes and their derivatives such as those corresponding to the general formula:
Figure imgb0002
 in which L represents a mono- or polydentate ligand and in particular an achiral phophine of general formula:
Figure imgb0003
 in which R represents an achiral alkyl, cycloalkyl aryl ayanat radical of 1 to 10 carbon atoms such as the methyl, ethyl, propyl, butyl, pentyles, hexyls, octyls, cyclohexyl, phenyl, toluyl radicals. Preferably L 1 is triphenylphosphine. Among the aforementioned rhodium derivatives, use is preferably made of the various rhodiumcarbonyls and in particular tetrarhodium dodecacarbonyl and hexarhodiumhexadecacarbonyl. Rhodium complexes taken in cationic form can also be used.

Comme phosphine chirale convenant à la mise en oeuvre de l'invention on peut utiliser aussi bien des monophosphines que des diphosphines. Comme exemples de monophosphines chirale on peut citer la diphénylmenthylphosphine, la phényldimenthylphosphine et la trimenthylphosphine. On préfère toutefois faire appel à des diphosphines chirales de formule générale:

Figure imgb0004
dans laquelle:

  • ― R1 et R2, identiques ou différents, représentent des radicaux hydrocarbonés ayant de 1 à 15 atomes de carbone,
  • - A représente un lien valentiel ou un radical organique divalent éventuellement substitué par un ou plusieurs groupes fonctionnels inertes,
As chiral phosphine suitable for implementing the invention, it is possible to use both monophosphines and diphosphines. Examples of chiral monophosphines that may be mentioned include diphenylmenthylphosphine, phenyldimenthylphosphine and trimenthylphosphine. However, it is preferred to use chiral diphosphines of general formula:
Figure imgb0004
 in which:
  • - R 1 and R 2 , identical or different, represent hydrocarbon radicals having from 1 to 15 carbon atoms,
  • - A represents a valential bond or a divalent organic radical optionally substituted by one or more inert functional groups,

l'un au moins des radicaux R" R2 et A étant chiral.at least one of the radicals R "R 2 and A being chiral.

Plus spécifiquement R, et R2, qui sont de préférence identiques, représentent des radicaux alcoyles ayant de 1 à 10 atomes de carbone (méthyle, éthyle, isobutyle, sec-butyle, sec-pentyle, éthyl-2 hexyle), cycloalcoyle ayant de 4 à 8 atomes de carbone cycliques (cyclobutyle, méthyle-1 cyclobutyle, cyclohexyle, méthyle-1 cyclohexyle, méthyle-2 cyclohexyle), aryles ou alcoylaryles (phényle, naphthyle, toluyle). A représente:

  • - un radical alcoylène linéaire ou ramifié ayant de 1 à 10 atomes de carbone, un radical cycloalcoylène ayant de 3 à 7 atomes de carbone cycliques, éventuellement susbtitué par 1 à 3 groupes alcoyles ayant de 1 à 4 atomes de carbone, un radical arylène, un radical polycyclique divalent, ces radicaux étant éventuellement substitués par 1 ou plusieurs groupes fonctionnels inertes et notamment 1 à 3 groupes alcoxy ayant de 1 à 4 atomes de carbone.
  • - un groupe hétérocyclique divalent (pyridylène, dioxa-1,3 cyclopentylène-4,5) ayant 1 ou 2 hétéroatomes tels que l'oxygène et/ou l'azote.
  • - un enchaînement de 1 ou plusieurs radicaux alcoylène et/ou cycloalcoylènes et/ou hétérocycliques et/ou polycycliques divalents tel que ceux définis précédemment.
  • - un enchaînement de groupes alcoylènes tels que ceux définis précédemment et de groupes amino tertiaire qui peuvent éventuellement être liés directement aux atomes de phosphore par l'intermédiaire de l'atome d'azote.
More specifically R, and R 2 , which are preferably identical, represent alkyl radicals having from 1 to 10 carbon atoms (methyl, ethyl, isobutyl, sec-butyl, sec-pentyl, 2-ethylhexyl), cycloalkyl having 4 to 8 cyclic carbon atoms (cyclobutyl, methyl-1 cyclobutyl, cyclohexyl, methyl-1 cyclohexyl, methyl-2 cyclohexyl), aryls or alkylaryl (phenyl, naphthyl, toluyl). A represents:
  • a linear or branched alkylene radical having from 1 to 10 carbon atoms, a cycloalkylene radical having from 3 to 7 cyclic carbon atoms, optionally substituted by 1 to 3 alkyl groups having from 1 to 4 carbon atoms, an arylene radical, a divalent polycyclic radical, these radicals being optionally substituted by 1 or more inert functional groups and in particular 1 to 3 alkoxy groups having from 1 to 4 carbon atoms.
  • - a divalent heterocyclic group (pyridylene, 1,3-dioxa-4,5-cyclopentylene-4,5) having 1 or 2 heteroatoms such as oxygen and / or nitrogen.
  • - A sequence of 1 or more alkylene and / or cycloalkylene and / or heterocyclic and / or polycyclic divalent radicals such as those defined above.
  • - A chain of alkylene groups such as those defined above and tertiary amino groups which may optionally be linked directly to the phosphorus atoms via the nitrogen atom.

Comme exemple de radicaux alcoylènes ont peut citer les radicaux méthylène, éthylène, propylène, éthyl-2 propylène; A peut encore représenter un radical cyclobutylène; cyclohexylène-1,4; méthyl-2 cyclohexylène-1,4; un radical ortho- ou p-phénylène; un radical diméthoxy-2,3 butylène-1,4.As an example of alkylene radicals, mention may be made of methylene, ethylene, propylene and 2-ethylpropylene radicals; A can also represent a cyclobutylene radical; 1,4-cyclohexylene; 2-methyl-1,4-cyclohexylene; an ortho- or p-phenylene radical; a 2,3-dimethoxy-1,4-butylene radical.

Comme exemple de radicaux A chiraux divalents formés par un enchaînement de radicaux alcoylènes et cycloalcoylènes ou hétérocycliques ou polycycliques ou amino on peut citer ceux de formules:

Figure imgb0005
Figure imgb0006
Figure imgb0007
Figure imgb0008
 As an example of divalent chiral radicals A formed by a chain of alkylene and cycloalkylene or heterocyclic or polycyclic or amino radicals, mention may be made of those of formulas:
Figure imgb0005
Figure imgb0006
Figure imgb0007
Figure imgb0008

Parmi les diphosphines chirales qui peuvent être utilisées dans le procédé selon l'invention on peut citer à titre non limitatif: le bis(diphénylphosphinométhyl)-1,2-cyclobutane (DPCB), le bis(di- méthylphophinométhyl)-1,2 cyclobutane, le bis(di-n-butylphosphinométhyl)-1,2 cyclobutane, le bis(dioctylphosphinométhyl-)-1,2 cyclobutane, le bis(ditolylphosphinométhyl-1,2 cyclobutane, le bis(dinaphtylphosphinométhyl)-1,2 cyclobutane, le bis(éthyl, hexylphosphinométhyl)-1,2 cyclobutane, le bisldiphénylphosphinométhyl)-1,2 cyclopentane; le bis(diphénylphosphinométhyl)-1,2 cyclohexane; le bis-(diméthylphosphinométhyl)-4,5 diméthyl-2,2 dioxolane-1,3, le bis-(diphénylphosphinométhyl)-4,5 diméthyl-2,2 dioxolane-1,3, (DIOP), le bis(ditolylphosphinométhyl)-4,5 diméthyl-2,2 dioxolane-1,3 le bis(diméthylphosphinométhyl)-1,2 acénaphtène, le bis(dibutylphosphinométhyl)-1 ,2 acénaphtène, le bis-(diphénylphosphinométhyl)-1,2 acénaphténe (DPA), le bis(ditolylphosphinométhyl)-1,2 acénaphtène. le bisldiphénylphosphino)-1,4 diméthoxy-2,3 butane (DDB), la tétramenthyldiphosphine; le bis (N,N'-diphénylphosphino)bis(N,N'(phényl-1 éthyl))diaza-1,4 butane.Among the chiral diphosphines which can be used in the process according to the invention, there may be mentioned, without implying any limitation: bis (diphenylphosphinomethyl) -1,2-cyclobutane (DPCB), bis (dimethylphophinomethyl) -1,2 cyclobutane , bis (di-n-butylphosphinomethyl) -1,2 cyclobutane, bis (dioctylphosphinomethyl -) - 1,2 cyclobutane, bis (ditolylphosphinomethyl-1,2 cyclobutane, bis (dinaphthylphosphinomethyl) -1,2 cyclobutane bis (ethyl, hexylphosphinomethyl) -1.2 cyclobutane, bisldiphenylphosphinomethyl) -1.2 cyclopentane; bis (diphenylphosphinomethyl) -1.2 cyclohexane; bis- (dimethylphosphinomethyl) -4.5 dimethyl-2,2 dioxolane-1,3, bis- (diphenylphosphinomethyl) -4,5 dimethyl-2,2 dioxolane-1,3, (DIOP), bis (ditolylphosphinomethyl ) -4.5 dimethyl-2,2 dioxolane-1,3 bis (dimethylphosphinomethyl) -1,2 acenaphthene, bis (dibutylphosphinomethyl) -1, 2 acenaphthene, bis- (diphenylphosphinomethyl) -1,2 acenaphthene (DPA ), bis (ditolylphosphinomethyl) -1,2 acenaphthene. bisldiphenylphosphino) -1,4 2,3-dimethoxy butane (DDB), tetramenthyldiphosphine; bis (N, N'-diphenylphosphino) bis (N, N '(1-phenylethyl)) diaza-1,4 butane.

Parmi les phosphines citées précédemment on utilise de préférence les bis(diarylphosphino- méthyl)-1,2 cyclobutanes décrits dans le brevet français no 73/18 319.Among the phosphines mentioned above, use is preferably made of bis (diarylphosphino-methyl) -1,2 cyclobutanes described in French patent No. 73/18 319.

Comme exemples de phosphines à atomes de phosphore chiral on peut citer la méthyl cyclohexyl orthométhoxyphényl phosphine; la méthylcyclohexylphénylphosphine; la benzylphénylméthyl- phosphine.As examples of phosphines with chiral phosphorus atoms, mention may be made of methyl cyclohexyl orthomethoxyphenyl phosphine; methylcyclohexylphenylphosphine; benzylphenylmethylphosphine.

Les complexes dérivés de Rh4 (CO),2 ou de Rh6 (CO)16 et des bis(diarylphosphinométhyl)-1,2 cyclobutanes conviennent tout particulièrement bien à l'hydrogenation asymétrique du néral et du géranial en énantiomères du citronellal car ils procurent à la fois une vitesse élevée d'hydrogénation, une bonne sélectivité en citronellal et une bonne pureté optique.Complexes derived from Rh 4 (CO), 2 or Rh 6 (CO) 16 and bis (diarylphosphinomethyl) -1,2 cyclobutanes are particularly suitable for asymmetric hydrogenation of the mineral and geranial to enantiomers of citronellal provide both a high rate of hydrogenation, good selectivity for citronellal and good optical purity.

La quantité de dérivé du rhodium mise en oeuvre dans le procédé de l'invention, exprimée en atomes-grammes de métal par mole d'aldéhyde diénique à hydrogéner peut varier dans de larges limites. Qu'il s'agisse du complexe préformé ou du dérivé apte à engendrer ce complexe dans les conditions de la réaction la quantité peut être choisie pour que le nombre d'atomes-grammes de rhodium par mole d'aldéhyde soit compris entre 1 × 10-4 et 1 × 10-1.The amount of rhodium derivative used in the process of the invention, expressed in gram atoms of metal per mole of diene aldehyde to be hydrogenated can vary within wide limits. Whether it is the preformed complex or the derivative capable of generating this complex under the conditions of the reaction, the quantity can be chosen so that the number of gram atoms of rhodium per mole of aldehyde is between 1 × 10 - 4 and 1 × 10 -1 .

Lorsque le complexe dérivé du rhodium/phosphine chirale est préparé "in situ", la quantité de phosphine engagée dans le processus dépend de la nature de la phosphine et de celle du dérivé du rhodium. Cette quantité, exprimée par le nombre d'atomes-grammes de phophore par atome-gramme de rhodium est telle que ce rapport peut varier entre 0,5 et 10; de préferénce le rapport P/Rh est compris entre 1 et 6. On pourrait cependant mettre en oeuvre des rapports P/Rh supérieurs à 10 sans sortir du cadre de la présente invention, mais celà ne procurerait aucun avantage particulier.When the rhodium / chiral phosphine complex is prepared "in situ", the amount of phosphine involved in the process depends on the nature of the phosphine and that of the rhodium derivative. This quantity, expressed by the number of gram atoms of phophore per gram atom of rhodium is such that this ratio can vary between 0.5 and 10; preferably the P / Rh ratio is between 1 and 6. However, P / Rh ratios greater than 10 could be used without departing from the scope of the present invention, but this would not provide any particular advantage.

La température à laquelle on conduit l'hydrogénation n'est pas critique et peut varier dans le larges limites. En général elle est comprise entre 0 et 150°C et de préférence entre 10 et 100°C. Il en est de même de la pression d'hydrogène qui peut varier entre 0,1 et 100 bars et de préférence entre 0,5 et 50 bars.The temperature at which the hydrogenation is carried out is not critical and can vary within wide limits. In general it is between 0 and 150 ° C and preferably between 10 and 100 ° C. It is the same for the hydrogen pressure which can vary between 0.1 and 100 bars and preferably between 0.5 and 50 bars.

Bien qu'il soit préférable de soumettre à l'hydrogénation asymétrique un aldéhyde diénique aussi pur que possible, c'est-à-dire pratiquement exempt de son isomère, on peut mettre en oeuvre du néral contenant jusqu'à 15% de géranial et vice versa.Although it is preferable to subject to asymmetric hydrogenation a diene aldehyde as pure as possible, that is to say practically free of its isomer, it is possible to use mineral containing up to 15% of geranial and vice versa.

De la même façon il est préférable d'utiliser une phosphine chirale ne contenant pas son énantiomère bien que l'on puisse opérer avec une phosphine chirale contenant moins de 15% de son énantiomère.In the same way it is preferable to use a chiral phosphine not containing its enantiomer although one can operate with a chiral phosphine containing less than 15% of its enantiomer.

L'hydrogénation asymétrique du néral ou du géranial est de préférence conduite dans un solvant inerte de l'aldéhyde et du catalyseur. Comme exemple de solvants, on peut citer des hydrocarbures (hexane, heptane, cyclohexane, benzène, toluène), des alcools (méthanol, éthanol), des nitriles (acétonitrile, benzonitrile).The asymmetric hydrogenation of the mineral or geranial is preferably carried out in an inert solvent of the aldehyde and the catalyst. Examples of solvents that may be mentioned include hydrocarbons (hexane, heptane, cyclohexane, benzene, toluene), alcohols (methanol, ethanol), nitriles (acetonitrile, benzonitrile).

Les exemples suivants illustrent l'invention et montrent comment elle peut être mise en pratique. Dans ces exemples on désignera par pureté optique P.0 le rapport du pouvoir rotatoire (α1)D du produit obtenu par le procédé au pouvoir rotatoire (α)D du produit mesuré dans les mêmes conditions, multiplié par 100, soit

Figure imgb0009
The following examples illustrate the invention and show how it can be practiced. In these examples, optical purity P.0 will denote the ratio of the rotary power (α 1 ) D of the product obtained by the process to the rotary power (α) D of the product measured under the same conditions, multiplied by 100, ie
Figure imgb0009

Par rendement optique on désigne la valeur de la pureté optique du produit que l'on obtiendrait par utilisation d'une phosphine optiquement pure.By optical yield is meant the value of the optical purity of the product which would be obtained by using an optically pure phosphine.

EXEMPLE 1EXAMPLE 1

Dans un ballon en verre de 50 cm3, équipé d'une arrivée de gaz par tube plongeant, d'un thermomètre, d'une agitation magnétique et d'un bouchon en verre permettant de procéder à des additions de réactifs ou des prélèvements de masse réactionnelle au moyen d'une seringue, on charge 18,2 mg de Rha (CO)16 (1,02 x 10-4 at-g de Rh), 67,5 mg (+)-(DPCB) soit 0,15 millimole, puis on purge l'appareil à l'azote et injecte 20 cm3 de toluène. On agite le contenu du ballon pendant 1 heure sous atmosphère d'azote puis ajoute 1,79 g (soit 11,77 millimole) de géranial contenant 5% de néral. On purge l'appareil à l'hydrogène puis maintient le contenu du ballon sous 1 bar d'hydrogène pendant 4 heures à 25°C. La réaction est arrêtée et la masse réactionnelle est soumise à une analyse chromatographique en phase gazeuse: le taux de transformation du géranial est de 100% et le rendement en citronellal de 99%. On évapore le solvant puis distille le résidu sous pression réduite. On recueille ainsi 1,28 g de 1-citronellal ayant un pouvoir rotatoire (α)25 D= -8,76° (mesuré sur une solution à 6 g pour 100 cm3 dans l'hexane) et (α)25 D=-9,1 ° mesuré en absence de solvant. Le pouvoir rotatoire du 1-citronellal pur (α)25 D mesuré sur une solution à 6 g/100 cm3 dans le cyclohexane est de -15,6°. Par référence à cette valeur, la P.O du produit obtenu est de 56%. Le pouvoir rotatoire du 1- citronellal pur (détermination sans solvant) est (α)25 D = -16° (cf. DONELL et al. Australian J. Chem. 19 525 [1966]).In a 50 cm 3 glass flask equipped with a gas inlet by dip tube, a thermometer, a magnetic stirrer and a glass stopper allowing reagents to be added or samples to be taken. reaction mass using a syringe, 18.2 mg of Rh a (CO) 16 (1.02 x 10- 4 at-g of Rh) are loaded, 67.5 mg (+) - (DPCB), ie 0 , 15 millimole, then the apparatus is purged with nitrogen and injected 20 cm 3 of toluene. The contents of the flask are stirred for 1 hour under a nitrogen atmosphere and then 1.79 g (or 11.77 millimole) of geranial containing 5% mineral are added. The apparatus is purged with hydrogen and then the contents of the flask are kept under 1 bar of hydrogen for 4 hours at 25 ° C. The reaction is stopped and the reaction mass is subjected to a gas chromatographic analysis: the geranial transformation rate is 100% and the citronellal yield 99%. The solvent is evaporated and then the residue is distilled under reduced pressure. 1.28 g of 1-citronellal having a rotary power are thus collected (α) 25 D = -8.76 ° (measured on a solution at 6 g per 100 cm 3 in hexane) and (α) 25 D = -9.1 ° measured in the absence of solvent. The rotary power of pure 1-citronellal (α) 25 D measured on a solution at 6 g / 100 cm 3 in cyclohexane is -15.6 °. By reference to this value, the PO of the product obtained is 56%. The rotary power of pure 1-citronellal (determination without solvent) is (α) 25 D = -16 ° (cf. DONELL et al. Australian J. Chem. 19 525 [1966]).

EXEMPLE 2EXAMPLE 2

On opère comme à l'exemple 1 sur les quantités suivantes:

Figure imgb0010
The procedure is as in Example 1 on the following quantities:
Figure imgb0010

La durée de réaction est de 10 heures

Figure imgb0011
The reaction time is 10 hours
Figure imgb0011

Après distillation on recueille 9,6 g citronellal de (α)25 D =--+ 10,15° (solution à 6 g/100 cm3 dans l'hexane) soit une pureté optique de 65%.After distillation, 9.6 g citronellal of (α) 25 D = - + 10.15 ° is collected (solution at 6 g / 100 cm 3 in hexane), ie an optical purity of 65%.

EXEMPLES 3 A 4EXAMPLES 3 TO 4

On opère comme à l'exemple 1 en remplaçant la (+)-DPCB par la (+)-DIOP. Le rapport géranial/Rh est de 120 et on utilise successivement un rapport P/Rh de 4 et de 6.The procedure is as in Example 1, replacing the (+) - DPCB with the (+) - DIOP. The geranial / Rh ratio is 120 and a P / Rh ratio of 4 and 6 is used successively.

Dans ces conditions on a obtenu les résultats suivants:

Figure imgb0012
Under these conditions, the following results were obtained:
Figure imgb0012

EXEMPLE 5EXAMPLE 5

On opère comme à l'exemple 1 en remplaçant la (+)-DPCB par la (-)-DPCB. Le rapport du nombre de mole de géranial (G) au nombre d'atomes-grammes de rhodium (G/Rh) est égal à 123 et le rapport P/Rh à 4. La (-)-DPCB a une pureté optique de 95,5%.The procedure is as in Example 1, replacing the (+) - DPCB with the (-) - DPCB. The ratio of the number of moles of geranial (G) to the number of gram atoms of rhodium (G / Rh) is equal to 123 and the ratio P / Rh to 4. The (-) - DPCB has an optical purity of 95 , 5%.

La durée de réaction est de 18 heures, le taux de transformation du géranial de 99%, le RT en citronellal de 99%. La pureté optique du (d)-citronellal obtenu est de 49% [(α)25 D = +7,7°: solution à 6 g/100 cm3 dans l'hexane]. Si l'on tient compte de la pureté de la phosphine le rendement optique s'élève à 52%.The reaction time is 18 hours, the geranial transformation rate of 99%, the RT into citronellal of 99%. The optical purity of the (d) -citronellal obtained is 49% [(α) 25 D = + 7.7 °: solution at 6 g / 100 cm 3 in hexane]. If the purity of the phosphine is taken into account, the optical efficiency is 52%.

EXEMPLE 6EXAMPLE 6

On opère comme à l'exemple 5 en remplaçant le géranial par le néral, les autres conditions étant par ailleurs identiques. On a obtenu les résultats suivants:

Figure imgb0013
The procedure is as in Example 5, replacing the geranial with the neral, the other conditions being otherwise identical. The following results were obtained:
Figure imgb0013

EXEMPLE 7EXAMPLE 7

On opère suivant le mode opératoire de l'exemple 1 et dans les mêmes conditions de pression et de température en remplaçant (Rh6(CO)16 par Rh4(CO)12. Le rapport P/Rh est de 3 et le rapport G/Rh de 120. Les résultats sont les suivants:

Figure imgb0014
The procedure is as in Example 1 and under the same pressure and temperature conditions, replacing (Rh 6 (CO) 16 by Rh 4 (CO) 12. The P / Rh ratio is 3 and the G ratio / Rh of 120. The results are as follows:
Figure imgb0014

EXEMPLE 8EXAMPLE 8

On opère comme à l'exemple 7 en remplaçant le géranial par le néral (le rapport N/Rh est de 140). On a obtenu les résultats suivants:

Figure imgb0015
The procedure is as in Example 7, replacing the geranial with the neral (the N / Rh ratio is 140). The following results were obtained:
Figure imgb0015

On opère comme à l'exemple 1 en portant le rapport N/Rh à 750 au lieu de 115 et le rapport P/Rh à 2. On a obtenu les résultats suivants:

Figure imgb0016
The procedure is as in Example 1, bringing the N / Rh ratio to 750 instead of 115 and the P / Rh ratio to 2. The following results have been obtained:
Figure imgb0016

Le néral utilisé contenait 7% de géranial.The mineral used contained 7% geranial.

EXEMPLES 10 à 18EXAMPLES 10 to 18

On opère selon le mode opératoire et les conditions de température et de pression de l'exemple 1, en faisant varier la nature de l'aldéhyde, de la phosphine chirale et du dérivé du rhodium. Les autres conditions et les résultats obtenus figurent dans le tableau suivant:

Figure imgb0017
The procedure is carried out according to the procedure and the temperature and pressure conditions of Example 1, by varying the nature of the aldehyde, chiral phosphine and the rhodium derivative. The other conditions and the results obtained are shown in the following table:
Figure imgb0017

EXEMPLE 19EXAMPLE 19

Dans un autoclave en acier inoxydable de 125 cm3 équipé d'un système d'agitation à secousses; on introduit une ampoule de verre de 35 cm3 contenant 10 cm3 de toluène, 18,3 mg de (-)-DPCB, 91,9 mg de RhH(CO) (PO)3 et 1,91 g de géranial. On ferme l'autoclave et introduit de l'hydrogène jusqu'à une pression de 25 bars. On maintient 17 heures dans ces conditions, puis l'autoclave est dégazé et le contenu de l'ampoule est traité et analysé comme à l'exemple 1.In a 125 cm 3 stainless steel autoclave equipped with a shaking system; a 35 cm 3 glass ampoule containing 10 cm 3 of toluene, 18.3 mg of (-) - DPCB, 91.9 mg of RhH (CO) (PO) 3 and 1.91 g of geranial are introduced. The autoclave is closed and hydrogen is introduced to a pressure of 25 bars. Maintained for 17 hours under these conditions, then the autoclave is degassed and the contents of the ampoule are treated and analyzed as in Example 1.

Le taux de transformation du géranial s'élève à 69% le rendement en citronellal par rapport au géranial transformé à 99% et la pureté optique à 60% (pouvoir rotatoire (a)25 = +6,6° mesuré sur le produit pur).The transformation rate of geranial is 69%, the yield of citronellal compared to geranial transformed at 99% and optical purity at 60% (rotary power (a) 2 5 = + 6.6 ° measured on the pure product. ).

Claims (18)

1. Process for the preparation of optically active citronellal, characterised in that neral or geranial is hydrogenated in the presence of a catalyst consisting of a complex which is soluble in the reaction medium and which is formed from a rhodium derivative and a chiral phosphine.
2. Process according to Claim 1, characterised in that the complex of rhodium and the chiral phosphine is prepared for immediate use.
3. Process according to Claim 1, characterised in that the complex of rhodium and the chiral phosphine is formed "in situ" from a rhodium derivative and a chiral phosphine.
4. Process according to Claim 3, characterised in that the rhodium derivative is a salt of a mineral or organic acid or a rhodium complex with an achiral ligand.
5. Process according to Claim 4, characterised in that the rhodium derivative is rhodium trichloride.
6. Process according to Claim 4, characterised in that the rhodium complex has the general formula:
Figure imgb0024
in which X represents a halogen atom, x is an integer from 1 to 4 and L represents a monoolefine or diolefine.
7. Process according to Claim 6, characterised in that the rhodium complex is µ, µ'-dichloro-bis-(cycloocta-1,5-diene-rhodium).
8. Process according to Claim 4, characterised in that the rhodium complex has the general formula:
Figure imgb0025
in which R represents an achiral alkyl, cycloalkyl or aryl radical having from 1 to 10 carbon atoms.
9. Process according to Claim 8, characterised in that the rhodium complex has the formula
Figure imgb0026
10. Process according to Claim 4, characterised in that the rhodium complex is a rhodium carbonyl taken from the group comprising tetrarhodium dodecacarbonyl and hexarhodium hexadecacarbonyl.
11. Process according to any one of Claims 1 to 10, characterised in that the chiral phosphine contains at least one chiral carbon atom and/or at least one chiral phosphorus atom.
12. Process according to Claim 11, characterised in that the chiral phosphine is a diphosphine of the general formula:
Figure imgb0027
in which R, and R2, which are identical or different, represent hydrocarbon radicals having from 1 to 15 carbon atoms and A represents a valence bond or a divalent organic radical which is optionally. substituted by one or more inert functional groups, at least one of the radicals R,, R2 and A being chiral.
13. Process according to Claim 12, characterised in that a chiral diphosphine of the formula (III) is used in which R, and R2 represent alkyl radicals having from 1 to 10 carbon atoms, cycloalkyl radicals having from 4 to 8 ring carbon atoms, or aryl or alkylaryl radicals, and A symbolises:
a) A linear or branched alkylene radical having from 1 to 10 carbon atoms, a cycloalkylene radical having from 3 to 7 ring carbon atoms which is optionally substituted by 1 to 3 alkyl radicals having from 1 to 4 carbon atoms, an arylene radical or a divalent polycyclic radical, it being possible for the said radicals to be substituted by one or more alkoxy groups having from 1 to 4 carbon atoms;
b) a divalent heterocyclic group having 1 or 2 heteroatoms from the group comprising oxygen and nitrogen;
c) an arrangement of 1 or more alkylene and/or cycloalkylene and/or heterocyclic and/or divalent polycyclic radicals such as those defined above under a) and b); or
d) an arrangement of alkylene groups, such as those defined above under a), and of tertiary amino groups which can be directly bonded to the phosphorus atoms via the nitrogen atom.
14. Process according to Claim 13, characterised in that a diphosphine of the formula (III) is used in which R, and R2 represent an aryl radical and A is a chiral group.
15. Process according to any one of Claims 11 to 14, characterised in that the chiral diphosphine is tetramenthyldiphosphine, 1,2-bis-(diphenylphosphinomethyl)cyclobutane, 4,5-bis-(diphenyl- phosphinomethyl)-2,2-dimethyldioxolane, 1,2-bis-(diphenylphosphinomethyl)acenaphthene, 1,4- bis(diphenylphosphino)-2,3-dimethoxybutane or [N,N'-bis-(diphenylphosphino)]-[N,N'-bis-(1-phenyl- ethy))]-1,4-diazabutane.
16. Process according to any one of Claims 1 to 15, characterised in that the amount of rhodium complex, expressed as the number of gram atoms of rhodium per mol of dienaldehyde, is between 1 x 10-4 and 1 x 10-1.
17. Process according to any one of Claims 1 to 16, characterised in that the amount of phosphine, expressed as the ratio of the number of gram atoms of phosphorus to the number of gram atoms of rhodium, is such that this ratio is between 1 and 6.
18. Process according to any one of Claims 1 to 17, characterised in that the hydrogenation is carried out at a temperature between 0 and 150°C and under a hydrogen pressure between 0.1 and 100 bars.
EP78420001A 1977-07-04 1978-06-14 Process for preparing optically active citronellal Expired EP0000315B1 (en)

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