I2-DMSO-Mediated N–H/α-C(sp3)–H Difunctionalization of Tetrahydroisoquinoline: Formal [2 + 2 + 1] Annulation for the Construction of Pyrrolo[2,1-a]isoquinoline Derivatives

An I 2 -DMSO-mediated cascade reaction using methyl ketones and 1,2,3,4-tetrahydroisoquinolines (THIQs) as commercially available substrates has been developed for the construction of pyrrolo[2,1- a ]isoquinoline derivatives. This metal-free process involves N–H/α-C(sp 3 )–H difunctionalization of THIQ. Two C–C bonds and one C–N bond are formed in one pot under mild conditions. Besides, a quaternary carbon center has been constructed in this transformation efficiently.