Application of Homophthalic Anhydrides as 2C Building Blocks in Catalytic Asymmetric Cyclizations of ortho-Quinone Methides: Diastereo- and Enantioselective Construction of Dihydrocoumarin Frameworks

摘要

A catalytic asymmetric [4+2] cyclization of ortho-quinone methides with homophthalic anhydrides in the presence of chiral squaramide-tertiary amine has been established. This method provides dihydrocoumarin frameworks in excellent diastereoselectivities (all 95:5dr) and high enantioselectivities (81%-98% ee). This reaction represents the first application of homophthalic anhydrides as 2C building blocks in catalytic asymmetric cyclizations. In addition, this approach not only provides a useful method for constructing enantioenriched dihydrocoumarin frameworks but also advances the chemistry of catalytic asymmetric cyclizations of ortho-quinone methides.