Chiral Phosphoric Acid‐Catalyzed Enantioselective Formal [4+2] Cycloaddition Between Dienecarbamates and 2‐Benzothioazolimines

Abstract An enantioselective chiral phosphoric acid catalyzed formal [4+2] cycloaddition between 2‐benzothiazolimines and N ‐H‐1,3‐dienecarbamates is described. A divergence in reaction pathways was observed depending on the dienes employed. The reaction performed with 4‐substituted dienes produced benzothiazolopyrimidines as major product in yields ranging from 42 to 67%, as single diastereoisomer and with enantioselectivity between 93 and 99%. The same reaction performed with 3‐substituted dienes, however, gave highly enantioenriched 1,2,3,4‐tetrahydroquinolines as the major products albeit with moderate diastereoselectivity. magnified image