I 2 -DMSO-Mediated N-H/α-C(sp 3 )-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.