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. (C) 2021 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.