Organocatalytic asymmetric [4+2] cyclization of 2-benzothiazolimines with azlactones: access to chiral benzothiazolopyrimidine derivatives

Abstract

An organocatalytic asymmetric domino Mannich/cyclization reaction between 2-benzothiazolimines with azlactones has been successfully developed. With the bifunctional squaramide catalyst, this formal [4+2] cyclization occurs with good to high yields and excellent stereoselectivities (up to 99% ee, >20 : 1 dr), providing an efficient and mild access to chiral benzothiazolopyrimidines bearing adjacent tertiary and quaternary stereogenic centers.