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Isomerization method
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A technology of compounds, carbon atoms, applied in the field of isomerization
Active Publication Date: 2015-01-14
MERCK PATENT GMBH
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Abstract
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The application of this chemical property to the cis / trans stereochemistry of 1,4-substituted cyclohexanes has not been studied so far
Method used
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Embodiment 1
[0058]
[0059] 20 g of starting material (64 mmol, 44% cis on central ring) were dissolved in 90 g of anhydrous dichloromethane (for analysis) and cooled to -45°C. 2 g of trifluoromethanesulfonic acid (13 mmol, 1.2 ml) were added to the suspension. Then 0.15 g of 1-adamantanol (1.0 mmol) in 9 g of dichloromethane was added dropwise. The batch was stirred at -40 to -45°C for an additional 1 to 3 hours, with occasional samples taken to measure the degree of isomerization. When isomerization was complete (sample was completely isomerized after 1-2 hours), the batch was processed.
[0060] For work-up, 38 ml of water were added to the batch, which was then warmed to about 20°C. The organic phase was separated off, washed with 22 g of trisodium citrate solution (25% in water) and 2×20 ml of water and evaporated to dryness in a rotary evaporator. The residue (20.2 g) was taken up in heptane and evaporated again. The crude product (pale yellow crystals) had a cis / trans conten...
Embodiment 2
[0063]
[0064] 168 g of starting material (525 mmol, 59.3% cis on central ring) were dissolved in 650 ml of anhydrous dichloromethane (for analysis) and cooled to -40 / -45°C. 9.5 ml of trifluoromethanesulfonic acid (108 mmol) were added to the suspension. 1.26 g of 1-adamantanol (8.3 mmol) in 50 ml of dichloromethane were then added dropwise. The batch was stirred at -40 to -45°C for an additional 1 to 2 hours, with occasional samples taken to measure the degree of isomerization. When isomerization was complete (sample was completely isomerized after 30 minutes), the batch was processed.
[0065] For work-up, a mixture of 175 g of ice and 350 ml of 25% hydrochloric acid was added to the batch, which was then warmed to about 20°C. The organic phase is separated off, washed with 175 ml of sodium bicarbonate solution (5% in water) and 175 ml of water and evaporated to dryness in a rotary evaporator. The residue (168.8 g) was taken up in heptane. The crude product (pale yel...
Embodiment 3
[0068] Example 1 was repeated while exchanging the catalyst 1-adamantanol for an equivalent amount of 2-chloro-2-methylpropane.
[0069] The crude product (pale yellow crystals) had 1.1% cis / trans product content, and 97.9% desired trans / trans product content (HPLC).
[0070] Other combinations of embodiments and variants of the invention can be derived from the claims.
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Abstract
#CMT# # / CMT# Preparing 1,4-trans-substituted cyclohexane compound (I), comprises reacting corresponding 1,4-cis-cyclohexane compound of (I) in the presence of a strong acid and an additional carbocation forming compound. #CMT# : # / CMT# Preparing 1,4-trans-substituted cyclohexane compound of formula (I), comprises reacting (I) corresponding 1,4-cis-cyclohexane compound in the presence of a strong acid and an additional carbocation forming compound. R1 : unsubstituted, linear up to 9C alkyl or -CH(CH 3)CH 3; R2 : H, halo, up to 9C alkyl, up to 9C perfluoroalkyl or up to 9C perfluoroalkoxy; s : 0-2; m : 1 or 2; n : 0-2; p : 1-4; q : 0-4; A1 : trans-1,4-cyclohexylene; Z1 : -(CH 2) t; and t : 0-4. #CMT#[Image]# / CMT# #CMT#USE : # / CMT# The method is useful for producing (I). #CMT#ADVANTAGE : # / CMT# The method: has mild procedure, less by-products; produces all-trans product with high purity and high trans content; and allows easy separation of the added catalyst. #CMT#ORGANIC CHEMISTRY : # / CMT# Preferred Method: The method is carried out in the presence of a superacid or perfluoroalkyl sulfonic acid. The reaction is carried out in the presence of at least one additive in the form of a secondary or a tertiary alkyl halide, a -sulfonate, a tertiary or a secondary alcohol, an alkyl ether or an alkanoic acid ester of these compounds. The method produces trans / trans bicyclohexane compound of formula (Ia). The reaction is carried out at = 0[deg] C. The reaction is carried out in chlorinated and / or fluorinated hydrocarbon as a solvent. The method comprises a hydrogenation of benzene ring, cyclohexene ring or cyclohexadiene ring to obtain (I) as a further step before the isomerization, where this ring is converted into a 1,4-substituted cyclohexane ring. Preferred Components: The configuration of the reaction product of each 1,4-substituted cyclohexane ring corresponds 95% or more of the trans-configuration. #CMT#[Image]# / CMT# #CMT#EXAMPLE : # / CMT# 4-methyl-4'-(3,4,5-trifluorophenyl)bi(cyclohexane) (44% cis-ring) (20 g) was dissolved in anhydrous methylene chloride (90 g) and cooled to -45[deg] C. Then trifluoromethane sulfonic acid (2 g) was added to the suspension. Then, 1-adamantanol (0.15 g) was added dropwise in dichloromethane (9 g). The mixture was stirred at -40 to -45[deg] C for 1-3 hours, and was isomerized. The mixture was worked up after complete isomerization (sample was isomerized completely after 1-2 hour) to obtain the all-trans-product.
Description
technical field [0001] The present invention relates to a process for the preparation of trans-1,4-disubstituted cyclohexane compounds having at least one residue derived from benzene in the 1- or 4-position, which process comprises the use of a strong acid and in the additional formation An isomerization step that converts one or more cis-configured cyclohexane rings to trans-configuration in the presence of a carbocationic compound. Background technique [0002] Functional chemicals are influenced not only by the functional groups present in them, but also to a crucial extent by their stereochemistry, ie their spatial structure. An important local field of stereochemistry focuses on simple nonaromatic rings and the relative positions of substituents on these rings. [0003] A fundamental issue in stereochemistry is the cis / trans isomerism of substituents on cyclohexane. The isomerization phenomenon of 1,4-substituted cyclohexane derivatives will be specifically discussed...
Claims
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Application Information
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