Stereocontrolled Construction of the 3,4‐Dihydrothiacarbazol‐2(9H)‐one Skeleton by Using Bifunctional Squaramide‐Catalyzed Cascade Reactions

An efficient approach for the stereocontrolled construction of the 3,4‐dihydrothiacarbazol‐2(9H)‐one skeleton has been developed. In the presence of a bifunctional squaramide catalyst that was derived from L‐tert‐leucine, the asymmetric tandem Michael/thiolysis reactions of 9‐methylindoline‐2‐thiones and N‐alkynoylphthalimides proceeded efficiently to furnish the desired 3,4‐dihydrothiacarbazol‐2(9H)‐one derivatives in satisfactory yields with high levels of enantioselectivity (up to 98 % ee).