Organocatalyzed Enantio- and Diastereoselective Formal Domino 1,3-Dipolar Cycloaddition/Rearrangement: Synthesis of Chiral Pyrrolo-thiazine-2-carbaldehydes.

An efficient approach for the synthesis of chiral pyrrolo[1,2-d][1,4]thiazine-2-carbaldehydes is achieved via formal 1,3-dipolar cycloaddition/rearrangement reactions of benzothiazolium salt and α,β-unsaturated aldehydes, utilizing an asymmetric organocatalyst. This process results in the formation of fluorescent, highly enantioenriched chiral molecules with three contiguous stereogenic centers, one of which is a chiral quaternary center, with excellent yields and enantio- and diastereoselectivity. A computational study demonstrated the understanding of the reaction mechanism. The synthetic utility of this protocol was successfully employed for gram scale synthesis. Fluorescent and in silico studies showed the application of the present methodology.