Chiral Phosphoric Acid-Catalyzed Enantioselective Formal [4+2] Cycloaddition Between Dienecarbamates and 2-Benzothioazolimines
By Wei-Yang Ma
Emeric Montinho-Inacio
Bogdan I. Iorga
Pascal Retailleau
Xavier Moreau
Luc Neuville
Géraldine Massona
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.
