Rongalite induced metal-free C(sp)-H functionalization of indoles: direct access to 3-(sulfonylmethyl) indoles.

A rongalite-induced C(sp)-H functionalization reaction has been developed for the synthesis of 3-(phenylsulfonylmethyl) indole derivatives from indole and arylsulfonyl hydrazides. This regioselective C-H functionalization provides a wide range of C-3 sulfonylmethyl indoles with upto 90% yields. Here, rongalite functions as a C1 unit source and a single electron donor. The use of inexpensive rongalite ( $0.03 per 1 g), mild reaction conditions and gram-scale synthesis are some of the key features of this methodology.