Electron‐rich O=PR3 compounds: Catalysts for alcohol silylation

The catalytic effect of a group of R₃P=O compounds was studied in a mild procedure for the silylation of primary alcohols, secondary alcohols, hindered secondary alcohols, and of hindered phenols in the presence of t‐butyldimethylsilyl chloride (TBDMSCl) and t‐butyldiphenylsilyl chloride (TBDPSCl). It was found that R₃P=O is an efficient catalyst in such reactions when R is a good electron‐donating group, such as Me₂N or n‐Bu and as an NMe(CH₂) moiety in N(CH₂CH₂NMe)₃P=O ( 3 ). However, R₃P=O is a weak or ineffective catalyst when R is a poor electron‐donating group, such as Ph or O‐n‐Bu or as a CH₂N‐o‐CH₂C₅H₄N moiety in N(CH₂CH₂N‐o‐CH₂C₅H₄N)₃P=O. Compound 3 , synthesized by oxidation of commercially available N(CH₂CH₂NMe)₃P, displayed the best catalytic properties for alcohol silylation in terms of efficiency, stability, and safety. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:21–26, 2001