Organocatalytic asymmetric synthesis of benzothiazolopyrimidines via a [4 + 2] cycloaddition of azlactones with 2-benzothiazolimines

Abstract

An easily available L-proline-derived guanidine-amide was found to be efficient at catalyzing a [4 + 2] cycloaddition of azlactones with 2-benzothiazolimines, affording various benzothiazolopyrimidines bearing adjacent tertiary and quaternary stereogenic centers in excellent yields at 2 mol% loading. The diastereoisomers of the main adducts differed from those in a previous bifunctional organocatalytic system.