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 metalfree 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.