Mild, effective and regioselective ring-opening of oxiranes using several thiosilanes promoted by tetrabutylammonium fluoride as catalyst

Abstract

The smooth and regioselective ring-opening of oxiranes with isothiocyanatotrimethylsilane 1 (TMSNCS), O-trimethylsilyl thioacetate 2 (TMSOCSMe) and phenylthiotrimethylsilane 3 (TMSSPh) proceeds under mild conditions promoted by 0.02 equiv. of TBAF (tetrabutylammonium fluoride) catalyst in a homogeneous system. In most cases, the TBAF catalyst works as an effective promoter. 1,2-Epoxyoctane 4, styrene oxide 5, glycidyl 4-(tert-butyl)benzoate 6, 1,2-epoxycyclohexane 7, methyl epoxybutanoate 8 and (2R)-glycidyl toluene-p-sulfonate 14 undergo smooth ring-opening in moderate to high yields. When ambiphilic TMSNCS 1 and TMSOCSMe 2 are used as reactants, the sulfur position exclusively attacks the oxiranes. No substantial thiirane formation and/or decyanation occurs when 1 is used. Deacetylation also fails to occur when 2 is used.