A general and efficient Lewis acid catalysed Mukaiyama-aldol reaction of difluoroenoxysilanes and ketones

We report a general and highly efficient Mukaiyama-aldol reaction of ketones and difluoroenoxysilanes.While the reaction of aryl ketones worked efficiently in the presence of Bi(OTf)_3, that of aliphatic ketones required the use of Sc(OTf_)3. In addition, Sc(OTf)_3 was capable of achieving excellent 1,2-selectivity in the corresponding reaction of α,β-unsaturated ketones. This method provides a facile access to differently substituted β-hydroxy α,α-difluoro ketones, versatile synthons for difluomethylated tertiary alcohols.

HFIP-catalyzed highly diastereoselective formal[4+2]cyclization to synthesize difluorinated multisubstituted chromans using difluoroenoxysilanes as C2 synthons

A hexafluoroisopropanol(HFIP)-catalyzed highly diastereoselective formal[4+2]cyclization between ortho-hydroxyphenyl para-quinone methides and difluoroenoxysilanes is developed.This tandem protocol provides a simple and straightforward approach to assemble diverse multiply functionalized difluorinated chromans with high to excellent diastereoselectivity by employing difluoroenoxysilane as a new C2 synthon.