Catalyst effects on the stereoselectivity of addition of tetrachloromethane to 1,3-cyclohexadiene

The stereoselectivity of addition reaction of tetrachloromethane with conjugate cyclodienes represented by 1,3-cyclohexadiene has been studied in respect to the type of catalyst, In all addition reactions the product of 1,4-addition, i.e. 1-chloro-4-(trichloromethyl)cyclohex-2-ene was formed exclusively consisting of two isomers (1a, 1d). Copper-amine complexes gave higher isomeric ratio 1a : 1d (up to 3.7) than ruthenium complex (1.3) at the same conditions (80 degrees C). Moreover, it was found that isomeric if ratio was temperature dependent and the highest valve (6.4) was obtained at lower temperature (20 degrees C). The results proved both catalyst and ligand effects on stereoselectivity of addition reaction of conjugated cyclic dienes. This supports a non-chain reaction mechanism because isomeric ratios of chain reactions are catalyst independent.