RU2191172C2 - Method of catalytic isomerization of endotetrahydrodicyclopentadiene to exo-tetrahydrodicyclopentadiene - Google Patents

Abstract

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to a method of synthesis of exo- tetrahydrodicyclopentadiene that can be used as a hydrocarbon fuel and parent monomers for synthesis of biologically active substances. Method involves the isomerization reaction of endo-tetrahydrodicyclopentadiene to exo-tetrahydrodicyclopentadiene when polychloromethane is added by drops to a reaction mass consisting of endo-tetrahydrodicyclopentadiene, an inert solvent and an organoaluminum compound. Chelate or salt of transient metal: PdCl₂,Pd(acac)₂,Ni(acac)₂. is used as a catalyst. Reaction is carried in argon atmosphere, under normal pressure and at temperature 10-60 C for 15-60 min. The mole ratio endo- tetrahydrodicyclopentadiene : organoaluminium compound : poly-chloromethane : salt (chelate) of metal = 100:9:32:0.1, respectively. Invention provides the development of the effective catalytic system providing 99.5% of the yield of the end product. EFFECT: improved method of isomerization, increased yield. 1 tbl, 7 ex

Description

 The invention relates to a catalytic process for the preparation of exo-tetrahydrodicyclopentadiene (exo-THDCPD) from endo-tetrahydrodicyclopentadiene (endo-THDCPD), an exhaustive hydrogenation product of an affordable and cheap cyclopentadiene dimer. Exo-TGCPPD is used as hydrocarbon fuels, starting monomers for the production of biologically active substances.

A known method of isomerization of endo-THDCPD in exo-THDCPD by double treatment of the starting reagent with concentrated sulfuric acid (US Pat. US 3381046, 1966) at temperatures of 90 and 95 ^o C for 26 hours. The resulting product is separated from the acid by centrifugation. The method is ineffective due to the low yield of the target product.

A known method for the catalytic isomerization of endo-THDCPD into an exo-isomer using Lewis acid as a catalyst, namely anhydrous AlCl ₃ (US Pat. US 4086284, 1978), added to the starting reagent, dissolved in an inert solvent, in an amount of 1- 75% relative to endo-TGCPPD at a temperature of 0 ^o C. After stirring the reaction mixture for 30 minutes, decanting from the precipitate, distilling off the solvent and separating the residual spent AlCl ₃ by washing, the product contains 96% exo-TGCPPD. The disadvantage of this method is the presence of significant quantities of undesirable by-products, such as decalin and adamantane.

A known method for the catalytic isomerization of endo-THDCP to the exo-isomer under the action of 0.7-5 wt.% Anhydrous AlCl ₃ in the presence of spent Nickel catalyst for the hydrogenation of cyclopentadiene dimer (US Pat. USA 4270014, 1981). The presence of the transition metal allows the process to be carried out at elevated temperatures up to 150 ^{° C.} without the formation of the above-mentioned undesirable by-products.

Thus, the only effective catalyst for the isomerization of endo-THDCPD to exo-THDCPD is anhydrous AlCl ₃ in the presence of a spent nickel hydrogenation catalyst. The disadvantages of this method include:
- the need to use anhydrous AlCl ₃ , which requires the use of special equipment for the implementation of the isomerization reaction
- the corrosion activity of AlCl ₃ requires the use of special grades of steel that are resistant to corrosion;
- the need for separation from the reaction products (dicyclopentadiene dimers) of the pyrophoric catalyst and AlCl ₃ .

 In order to expand the assortment of catalytic systems that allow the isomerization of endo-THDCPD to exo-THDCPD effectively, the present invention proposes a catalytic system consisting of an organoaluminum compound, polychloromethane and transition metal complexes.

The essence of the action of the catalytic system is the interaction of the starting endo-TGCPPD with the organoaluminum compound (AOC) R ₃ Al, R ₂ AlH, R _n AlCl _3-n , where R = C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ ; n is 1; 1.5; 2 and polychloromethane (Cl ₄ or CHCl ₃ ) in the presence of a complex or transition metal salt (PdCl ₂ Pd (acac) ₂ , Ni (acac) ₂ ), taken in a molar ratio of 100: 9: 32: 0.1. In order to avoid a violent exothermic reaction between AOS and polychloromethane, the reagents are mixed at a slightly lower or room temperature of 10-20 ^o C, adding polychloromethane to the mixture slowly dropwise. A further reaction is carried out depending on the activity of the reaction system at room temperature or with slight heating to 40 ^{° C.} and atmospheric pressure. The reaction time is 15-60 minutes. As a solvent, exo-THDCPD or some inert solvent (pentane, hexane, heptane) can be used. The conversion of endo-THDCPD is 100%. The yield of the target product is 99.5%. Along with the target product, the formation of a small amount of polychloromethane conversion products (in the case of CCl ₄ —CHCl ₃ and CH ₂ Cl ₂ ) is observed, which, if necessary, are easily distilled off together with an inert solvent. The formation of by-products such as transdecalin is not noted. Another possible adamantane product is formed in trace amounts under the indicated conditions. Its formation in noticeable amounts is possible with increasing reaction temperature.

The end of the reaction is easily detected by the stratification of the reaction mixture into two miscible phases: the upper almost colorless transparent layer, which, according to gas-liquid chromatography, consists of the target product exo-THDCPD, an inert solvent (if added), and a small amount of CHCl ₃ and CH ₂ Cl ₂ ; the lower layer is a dark viscous mass consisting of the products of transformation of an organoaluminum compound insoluble in saturated hydrocarbons, spent transition metal complexes, and heavy products of the conversion of polychloromethane. The target product is isolated from the reaction mixture by simple decantation and does not contain organoaluminum compounds and the initial polychloromethane.

АОС: R₃Al, R₂AlH, R_nAlCl_3-n, где R= C₂H₅, С₃H₇, С₄H₉; n=1, 1,5, 2, СН_4-mCl_m: m=3, 4 (СНСl₃, CCl₄); M: PdCl₂, Pd(acac)₂, Ni(acac)₂.The reaction proceeds according to the scheme.

AOC: R ₃ Al, R ₂ AlH, R _n AlCl _3-n , where R = C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ ; n = 1, 1.5, 2, CH _4-m Cl _m : m = 3, 4 (CHCl ₃ , CCl ₄ ); M: PdCl ₂ , Pd (acac) ₂ , Ni (acac) ₂ .

Significant differences of the proposed catalytic system:
The proposed catalytic system is based on the use of an organoaluminum compound and polychloromethane, during the interaction of which, in the presence of catalytic amounts of transition metal compounds, endo-TGCPD is quantitatively involved in the catalytic isomerization reaction in exo-TGCPD.

 Using the proposed catalytic system allows quantitatively with the release of 99.5% to obtain exo-TGCPPD at low temperatures and atmospheric pressure.

The invention is illustrated by the following example:
In a 50 ml glass reactor mounted on a magnetic stirrer, 6 ml of pentane, 1.324 g of endo-TGCPD, 10.8 mg of PdCl ₂ , 1 ml of diisobutyl-aluminum hydride are placed in an argon atmosphere. Then, to prevent a violent reaction at a temperature of 10-12 ^° C., CCl ₄ , previously diluted with 2 ml of pentane, was added dropwise. After 40 minutes, the reaction mixture is stratified into 2 layers. The top layer was selected and passed through Al ₂ O ₃ . The resulting clear liquid contains 99.5% of the desired product exo-TGCPPD. The quantity is determined by GLC using the internal standard method.

The structure of the compound was proved by ¹³ C NMR: (δ, ppm) С1, С7 - 48.42, С2, С6 - 40.88, С3, С5 - 28.98, С4 - 27.48, С8, С9 - 32.69, С10 - 32.10. For comparison, endo-THDCPD has the following chemical shifts: C1, C7 - 45.76, C2, C6 - 41.85, C3, C5 - 27.16, C4 - 28.98, C8, C9 - 23.26, C10 - 43.48 ppm.

 Other examples confirming the method are given in the table.

Claims (1)

Method for catalytic isomerization of endo-tetrahydrodicyclopentadiene in exo-tetrahydrodicyclopentadiene, characterized in that to the reaction mass consisting of endo-tetrahydrodicyclopentadiene dissolved in an inert solvent and an organoaluminum compound (AOC) R ₃ Al, R ₂ Al ₃ R _n Al _{3 n n} Al where R = C ₂ H ₅ , C ₃ H ₇ , C ₄ H ₉ ; n = 1, 1,5, 2, polychloromethane (CCl ₄ or CHCl ₃ ) is added dropwise in a molar ratio of 100: 9: 32, respectively, and the reaction is carried out in the presence of a complex or a transition metal salt of PdCl ₂ , Pd (acac) ₂ , Ni (acac) ₂ as a catalyst taken in an amount of 0.1 mol. % with respect to the initial endo-tetrahydrodicyclopentadiene, in an argon atmosphere, at atmospheric pressure and a temperature of 10-40 ^o C for 15-60 minutes

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