Organocatalytic formal [4 + 2] cycloaddition of o-quinone-methyl derivatives and 2-isocyanatomalonate diesters for the construction of chroman derivatives with adjacent quaternary chiral centers

Abstract

An asymmetric organocatalytic formal [4 + 2] cycloaddition/annulation cascade of ortho-quinone methides with 2-isocyanatomalonate diesters has been reported. Chromans bearing three contiguous stereogenic centers with a chiral orthoester skeleton were obtained in high yields with excellent enantio- and diastereoselectivities (up to 93% yield, 99% ee and >20 : 1 dr) by using a tertiary amino-urea catalyst.