ADDITION OF TRICHLOROSILANE TO CYCLIC OLEFINS

The addition of trichlorosilane, in the presence of chloroplatinic acid, to 1-, 3-, and 4-ethylcyclohexenes as well as to ethylidene- and vinylcyclohexanes was studied in detail. In every case, the major product was 2-cyclohexylethyltrichlorosilane. In the reaction with the ethylcyclohexenes, the recovered olefin fraction was found to contain all the possible monoolefin isomers except vinylcyclohexane. Contrary to reports, 1-n-propyl-cyclohexene also adds trichlorosilane in the presence of chloroplatinic acid to form 3-cyclohexylpropyltrichloro-silane. The unchanged olefins recovered from this reaction are composed again of a mixture of the various isomers. The above findings now eliminate the necessity for invoking anything but a smooth, consecutive double-bond shift along the chain in these cyclic systems as suggested by the mechanism of Harrod and Chalk. Platinum complexes, like dichlorobis(ethylene)-µµ-dichloro-diplatinum(II) and dichlorobis(ethylcycIohexene)-µ,µ-dichloro-diplatinum(II), were also effective catalysts in producing terminal adducts in the reaction of 1-ethylcyclohexene with trichlorosilane, while platinum on charcoal was not. This, in conjunction with other qualitative observations which were made, suggests that a soluble platinum complex, rather than platinum metal itself, is the active catalyst in such systems. © 1968, American Chemical Society. All rights reserved.