Amines<i>vs. N</i>-Oxides as Organocatalysts for Acylation, Sulfonylation and Silylation of Alcohols: 1-Methylimidazole<i>N</i>-Oxide as an Efficient Catalyst for Silylation of Tertiary Alcohols

A comparison of the relative catalytic efficiencies of Lewis-basic amines vs. N-oxides for the acylation, sulfonylation and silylation of primary, secondary and tertiary alcohols is reported. Whilst the amines are generally superior to the N-oxides for acylation, the N-oxides are superior for sulfonylation and silylation. In particular, 1-methylimidazole N-oxide (NMI-O) is found to be a highly efficient catalyst for sulfonylation and silylation reactions. To the best of our knowledge, NMI-O is the first amine or N-oxide Lewis basic organocatalyst capable of promoting the efficient silylation of tert-alcohols in high yield with low catalyst loading under mild reaction conditions.