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
[reaction: see text] A gold(I) complex of Xantphos AuCl(xantphos) catalyzes the dehydrogenativesilylation of alcohols with high chemoselectivity and solvent tolerance. It is selective for the silylation of hydroxyl groups in the presence of alkenes, alkynes, alkyl halides (RCl, RBr), ketones, aldehydes, conjugated enones, esters, and carbamates.
Alcohols, phenols and carboxylic acids are silylated with very good yields in the presence of silyl methallylsulfinates under non-basic conditions and with the formation of volatile co-products.
The primary alcohols 1a-d and ethers 4a-b were effectively reduced into the corresponding hydrocarbons 2 by HSiEt3 in the presence of catalytic amounts of B(C6F5)(3). The secondary alkyl ethers 4g,h underwent cleavage and/or reduction under similar reaction conditions to produce either the silyl ether 3k or the corresponding alcohol 5b upon subsequent deprotection with TBAF. The secondary alcohols (1g,h) and tertiary alcohol 1i, as well as tertiary alkyl ether 4i, did not react with the HSiEt3/(B(C6F5)(3) reducing reagent at all. The following relative reactivity order of substrates was found: primary>>secondary>tertiary. The methyl aryl ethers 4c-e and alkyl aryl ether 4f were smoothly deprotected to give the corresponding silyl ethers 3b,h-j in nearly quantitative isolated yields. (C) 1999 Elsevier Science Ltd. All rights reserved.
Cationic Dirhodium Complexes Bridged by 2-Phosphinopyridines Having an Exquisitely Positioned Axial Shielding Group: A Molecular Design for Enhancing the Catalytic Activity of the Dirhodium Core
create highly electrophilic dirhodium catalysts. The electrophilicity of lantern-type dirhodium complexes is generally decreased by the coordination of a ligand to the axial site, which often causes a reduction in the catalytic activity. We designed and synthesized a series of cationic dirhodium complexesbridged by 2-diarylphosphinopyridines having a bulky 2,4,6-triisopropylphenyl (Tip) group that can