Chemoselective functionalization of α-carbolines at the C-2, C-3, C-4, and C-6 positions using Suzuki–Miyaura reactions

The synthesis of 2-, 3-, 4-, and 6-substituted pyrido[2,3-b]indoles (α-carbolines) by palladium-catalyzed cross-coupling reactions from the corresponding halopyrido[2,3-b]indoles is described. A sequential and a one-pot chemoselective double Suzuki–Miyaura coupling route is presented for the synthesis of symmetrically and unsymmetrically disubstituted pyrido[2,3-b]indoles.