We report highly efficient asymmetric [3 + 2] cycloadditions of thiazolium salts with either methyleneindolinone derivatives or chalcone derivatives by a chiral N,N'-dioxide/MgII complex catalyst, providing hydropyrrolo-thiazole derivatives in high yields and enantioselectivities. The thiazolium salts or the thiazole adducts enable rearrangement via C-S bond cleavage to give 1,4-thiazine derivatives, which is not only interesting and useful to expand the application of such [3 + 2] cycloaddition, but also made the reactions complicated and challenging. Considering the potential applications and challenge of constructing vicinal multi-stereocenters of pyrrolo-[1,4]thiazine skeleton, we report highly efficient asymmetric [3 + 2] cycloaddition/rearrangement cascade reactions of thiazolium salts with β,γ-unsaturated α-ketoesters by chiral NiII complex under mild reaction conditions to yield pyrrolo-[1,4]thiazine derivatives with a broad substrate compatibility.

Enantioselective [3 + 2] cycloaddition and rearrangement of thiazolium salts to synthesize thiazole and 1,4-thiazine derivatives

2019 Fall National Meeting

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