The primary alcohols 1a-e and ethers 4a-d were effectively reduced to the corresponding hydrocarbons 2 by HSiEt(3) in the presence of catalytic amounts of B(C(6)F(5))(3). To the best of our knowledge, this is the first example of catalytic use of Lewis acid in the reduction of alcohols and ethers with hydrosilanes. The secondary alkyl ethers 4j,k enabled cleavage and/or reduction under similar reaction conditions to produce either the silyl ethers 3m-n or the corresponding alcohol 5a upon subsequent deprotection with TBAF. It was found that the secondary alcohols 1g-i and tertiary alcohol 1j, as well as the tertiary alkyl ether 4l, did not react with HSiEt(3)/(B(C(6)F(5))(3) reducing reagent at all. The following relative reactivity order of substrates was found: primary >> secondary > tertiary. A plausible mechanism for this nontraditional Lewis acid catalyzed reaction is proposed.

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A Novel B(C 6 F 5 ) 3 -Catalyzed Reduction of Alcohols and Cleavage of Aryl and Alkyl Ethers with Hydrosilanes.-Primary alcohols and ethers as well as the alcohols (Ie) and (If) containing two or three phenyl groups undergo a novel, nontraditional reduction to hydrocarbons with hydrosilanes in the presence of B(C 6 F 5 ) 3 . In contrast, other secondary and tertiary alcohols as well as secondary alkyl ethers and alkyl aryl ethers undergo O-silylation. Interestingly, the reactivity order for this reduction of primary, secondary, and tertiary substrates is completely reverse to that observed in classical protocols.