Organocatalytic Asymmetric Formal [3+2] Cycloaddition Reaction of Isocyanoacetates with Saccharin-Derived 1-Azadienes

An efficient organocatalytic diastereo-, enantioselective formal [3+2] cycloaddition reaction of α-isocyanoacetates with saccharin-derived 1-azadienes catalyzed by dihydroquinine derived squaramide catalyst has been investigated, furnishing the corresponding directly linked benzo[d]isothiazole 1,1-dioxide-dihydropyrroles with two adjacent tertiary-quaternary stereocenters in high yields (up to 98%), moderate to excellent stereoselectivities (up to >20:1 dr and 97% ee ) under mild conditions.