Abstract
The platinum-catalyzed hydrosilylation of unsymmetrical substituted arylalkynes with various hydrosilanes was investigated and the reaction selectivity of various para -substituted substrates was compared with that of their corresponding ortho -substituted derivatives. We showed that heterogeneous platinum oxide is a very efficient catalyst for such hydrosilylations and that H-Si bond addition proceeds in a stereoselective cis -fashion. The regioselectivity was found to be under the control of the ortho -substituent rather than due to the nature of the platinum catalyst. Arylalkynes with an ortho -substituent provided predominantly to exclusively α-selectivity, regardless of the electronic nature of the substituent. The precise contributions of steric, electronic, and coordinative factors controlling the regioselectivity of the H-Si bond addition are discussed.
Key words
hydrosilylation - platinum oxide - vinylsilane - alkyne
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