CS242645B1 - Production method of heterogenised chirale catalysts on the base of phosphine complexes with rhodium - Google Patents

Description

The invention relates to a process for the production of heterogeneous transition metal complex chiral catalysts using inorganic materials with higher utility values, in particular high stereoselectivity, as carriers.

It is known that chiral metal complexes are used as homogeneous catalysts for many reactions because they are characterized by high reactivity and selectivity.

A fundamental disadvantage of these homogeneous systems is the difficulty in separating the catalysts from the reaction mixture and the associated costly recovery of the catalysts. Attempts have been made to eliminate this drawback by immobilizing homogeneous complexes, preferably on both organic and inorganic supports. Such processes for the preparation of heterogeneous complex catalysts are known, and in most cases the production of achiral systems has been carried out. The number of donor-ligand systems is also considerable, and the introduction of trivalent phosphorus as a donor results in versatile complex catalysts, such as disclosed in the inventions of OE-US 23 32 167, 20 62 352 and 20 62 351 00 104 966, No. 4,134,906 and 4,151,114. The subject is also discussed in several review articles, see, e.g., Allum et al. in 0.Organometal.Chem. 87 (1975) 203.

The organic polymers contemplated as carriers exhibit a substantially improved ability to be separable, but the strong dependence of their activity on the swelling state in the various solvents is a drawback. This drawback can be overcome by the use of inorganic carrier components. Therefore, experiments favoring inorganic carriers have been carried out more frequently.

Unlike the most commonly used achiral phosphino2

242 64S ligands, chiral phosphine ligands were fixed to inorganic carriers in only a few cases.

Thus, CS 165 139 describes (-) - 2,3-isopropylidene-2,3-dihydroxy-1,4-bis (diphenylphosphino) butane fixed on macroporous silica gel and used in the form of rhodium complexes to hydrosilylate ketones and hydrogenate enamides to form carboxylic acids.

The silylated tertiary phosphine containing the chiral β-substituent was bound to silica gel and used as a rhodium complex on similar substrates as described in M. Capka, Coll. 42 (1977) 3410.

□ other chiral rhodium complexes were immobilized on clay minerals such as hectorite, bentonite or halloysite using ion exchange or physical absorption techniques and used in asymmetric hydrogenations according to 00 139 251.

The latter systems are characterized by reduced capacity and are therefore not very suitable for practical use.

The disadvantages of the silylated ligands prepared hitherto and of the heterogeneous systems produced therefrom are that only catalysts can be obtained which, in catalytic hydrogenations, differ considerably from homogeneous catalysts in kinetic parameters and in stereoselectivity. By using phosphine donors with a chiral β-substituent, diastereomeric tertiary silylated phosphines are formed upon fixation on the support, which cannot be separated from each other, which should be regarded as a deficiency thereof.

The above disadvantages are lessened by the process for the preparation of heterogeneous rhodium-complexed phosphine-complexed chiral catalysts according to the invention, which comprises treating rhodium complexes selected from (Rh (ethylene) ₂ Cl), (Rh (1,5cyclookten) Cl ₎ , / Rh (norbornadiene) Cl / ₂ / Rh (cyclooctatetraene) Cl / ₂ by chiral silylated tertiary phosphines formed by the interaction of the inorganic support material containing hydroxyl groups, for example silica with compounds of formula 1-RJSI ÍCHgjj -PR ^ ^ ² (I) .

64S 242 wherein R is halogen or an alkoxy radical with an alkyl radical C-C _and, preferably, methoxy or ethoxy radical,

RR configuration of the same, enantiomerically uniform C _Q to radicals as bornyl radical, preferably menthyl or neomenthyl radicals, and n is 1 to 18, preferably 3 to 7 and particularly preferably 5, prepared by the reaction of trihalogen- or trialkoxysilanes of formula II

R ₃ Si-X (II) »wherein X represents an alkenyl or haloalkyl radical and wherein R is as described above, with secondary chiral phosphines having the same substituent configurations or their alkali metal salts of the general formula

HPR ¹ R ² or MPR 1 R ² , wherein M is lithium, sodium or potassium and wherein RRs correspond to two configurationally identical, enantiomerically uniform residues of the previously described meaning.

The process of the invention brings a number of advantages. The method for preparing silylated chiral phosphines is universally applicable. By using secondary chiral phosphines with the same substituent configurations, enantiomerically uniform ligands are fixed on the support. The use of chiral Si-C-P derivatives succeeds in the preparation of silyl phosphines with different spacer lengths - anchor ligands, which can be adapted in this way to the requirements of the catalytic reactions.

Polymeric metal complexes which are particularly well suited for catalytic reactions with high stereoselectivity and high reaction rates can be prepared by polymer complexes produced in this manner by known complexing reactions.

Example 1 mmol of dimenthylphosphine was dissolved in 80 ml of ether-free water. 48 mmol of a solution of butyllithium in hexane were added, the solution initially turning yellow, then orange.

The solution of the resulting lithium dienthylphenafide was stirred at -15 ° C

242,645, with stirring, an excess of chloromethyltriethoxysilane - 115 mmol was added dropwise. The solution slowly decolorized to form a colorless precipitate. This was filtered and the solvent was removed from the filtrate. The phosphinosilane was vacuum distilled at a pressure of 5 x 10 2 mm Hg. 50 g of silica gel 100, heated at 180 ° C for 5 hours under high vacuum under argon, was refluxed with 0.017 mmol of the prepared phosphinosilane dissolved in 250 ml of absolute toluene. Then about 100 ml of toluene was distilled off and 100 ml of fresh toluene was added. The mixture was filtered, extracted three times with 100 ml of toluene each time and dried under high vacuum. The phosphorus content of the preparation was 0.35%. 20 g of the fixed phosphine support were reacted at room temperature with 0.107 g / Rh (C ₂ H ₄ ) ₂ Cl / ₂ in 80 ml of benzene. The reaction mixture was left to stand overnight, aspirated, extracted with toluene 30 times and freeze dried. · The rhodium content of the resulting catalyst was 0.07% ·

Example 2

3-Chloropropyltriethoxysilane was added dropwise with an excess of 10 mmol to the solution of the prepared lithium dimethyl phosphide prepared according to Example 1, while cooling with ice and stirring. Work-up was carried out as described in Example 1. 50 g of silica gel 100 were reacted with 0.017 mmol of phosphinosilane as described in Example 1. The product was converted to the rhodium complex by a procedure analogous to Example 1. The rhodium content was 0.1%.

Example 3

Analogously to Example 2, 5-bromopentyltriethoxysilane was added dropwise to the solution of the phosphide prepared in Example 1 in excess of 15 mmol. After work-up, the product was distilled. 50 g of silica gel 100 was reacted with 0.017 mmol of phosphinosilane as described in Example 1. The phosphorus content was 0.28%. The prepared product was processed analogously to Example 2. The rhodium content was 0.16%.

EXAMPLE 4 242,645 mmol of acetamidocinnamic acid in 15 ml of anhydrous methanol was hydrogenated in a hydrogenation apparatus in the presence of 0.01 mmol of heterogenized rhodium catalysts according to Examples 1, 2 and 3 at 25 ° C and 1 atm Hg. Treatment of the hydrogenation products was carried out as described by T. P. Oeng

in 0.Organometal Chem. 91, 105 (1975). Optical rotation was measured in ethanol. Catalyst Time Conversion Optical yield from the example reaction (h) (%) (%) 1 14.5 100 ALIGN! 67.0 2 5.0 100 ALIGN! 80.4 3 3.0 100 ALIGN! 86.9 Example 5 1 mmol of itaconic acid was, like described in the example 4, hydrogenated to presence Catalysts of Examples 1, 2 and 3 until complete conversion. The catalyst was filtered off, solution at room temperature at room temperature to dryness , residue dried in desiccator and fixed optical rotation in ethanol. Catalyst Time Conversion Optical yield from the example reaction (h) (%) (%) 1 20 May 67 82.6 2 54 100 ALIGN! 43.8 3 71 94 61.5

Example 6 mmol of acetamidoacrylic acid and 0.02 mmol of the catalyst of Example 1 were hydrogenated as described in Example 4.

242 645 complete hydrogenation, the catalyst was separated, the solution was concentrated to dryness at room temperature, the residue was dissolved in 10 ml of H 2 O and stirred for 30 minutes. The undissolved residues were then separated and the aqueous solution was concentrated to 2 ml. After evaporation of the remaining solvent, the product was dried in a desiccator over CaCl 2. Final drying took 2 hours at 35 ° C. Optical rotation was determined in water. After 7 hours, an optical yield of 18% was achieved at 100% conversion.

Example 7 mmol of acetamidocinnamic acid methyl ester and 0.01 mmol of the heterogeneous catalyst of Example 2 were hydrogenated as described in Example 4. Gas chromatographic analysis showed a conversion of 70% after 78 hours at an optical yield of 9%.

Claims (2)

OBJECT OF THE INVENTION 242 645 Wherein M is lithium, sodium or potassium, and wherein R R is two configurationally identical, enantiomerically uniform, residues as previously described. Process for the preparation of heterogeneous chiral catalysts based on rhodium complexes of phosphines, characterized in that rhodium complexes selected from / Rh (ethylene) ₂ Cl / ₂ , / Rh (1,5-cyclooctene) Cl / ₂ , / Rh (norbornadien) Cl / ₂ and / Rh (cyclooctatetraene) Cl / ₂ to chiral silylated tertiary phosphines formed by the interaction of an inorganic carrier material containing hydroxyl groups, for example silica, with compounds of formula 1 R ₃ Si- (CH ₂ ) _n -PR ¹ R ² (I). wherein R represents halogen or alkoxy radical with an alkyl radical _C-C, preferably the methoxy radical or the 2-carboxylic etbo1, R and R configuration same single enantiomerically Οθ to C ₁₂ radicals, such as bornyl radical, preferably menthyl or neomenthylové residues n and n are 1 to 18, preferably 3 to 7 and particularly preferably 5, prepared by reaction of the trihalogen or trialkoxysilanes of the general formula II R ₃ Si-X (II), wherein X is an alkenyl or haloalkyl radical and wherein R is as described above, with secondary chiral phosphines having the same configuration of substituents or their alkali metal salts of the general formula HPrV or MPR ^ ² 2. A method according to claim 1, wherein the chiral silylated tertiary phosphines are allowed to interact with the anor242 645 ganic carrier material to achieve phosphorus coverage values of from 0.28 to 0.7%, preferably 0.3% based per carrier weight.