Rh(III)-Catalyzed Tandem Acylmethylation/Nitroso Migration/Cyclization of N-Nitrosoanilines with Sulfoxonium Ylides in One Pot: Approach to 3-Nitrosoindoles.

A novel synthesis of 3-nitrosoindoles starting from easily available N-nitrosoanilines and sulfoxonium ylides via Rh(III)-catalyzed acylmethylation and trifluoroacetic acid (TFA)-mediated nitroso transfer/cyclization cascade reaction in one pot has been developed. The N-nitroso group plays a dual role as a versatile directing group and internal nitrosation reagent. Rh(III)-catalyzed C-H activation/C-C bond formation and TFA-mediated N-N bond cleavage/formation of two C-N bonds are involved in this reaction. This process is scalable and avoids external oxidation. DMSO and H2O are produced as byproducts. Moreover, further chemical transformations of the desired products enhance its synthetic value.