Multiple annulations of inert C(sp2)-H bonds with alkynes

Abstract

Transition-metal catalyzed directing group (DG) assisted annulation of inert C-H bonds leads to the formation of complex molecular frameworks from readily accessible substrates. Thus, multiple annulation of less functionalized substrates with unsaturated species leads to the construction of structurally diverse fused poly(hetero)cycles. The directed inert C(arene)-H bond activation and the mode of TM-migration in this process could enabled obatining L-type [involves DG heteroatom, o-C(arene)-H bond, and C(arene)-H bond of aryl-motif in alkyne], Y-type [involves two heteroatoms of the DG and o-,o'-C(arene)-H bonds], and B-type [involves o-C(arene)-H bond and m-C(arene)-H bond] π-extended annulation products. The coordination preference of the DG heteroatom makes the transformation chemo- and regio-selective. This article underlines the conceptual development of unsymmetrical multiple annulation of arene C(sp²)-H bonds with alkynes, which is exceedingly appealing and highly important.