Synthesis of naphtho[1′,2′:4,5]imidazo[1,2-a]pyridines via Rh(iii)-catalyzed C-H functionalization of 2-arylimidazo[1,2-a]pyridines with cyclic 2-diazo-1,3-diketones featuring with a ring opening and reannulation

An unprecedented synthesis of functionalized naphtho[1 ' ,2 ' :4,5]imidazo[1,2-a]pyridines via rhodium-catalyzed cascade reactions of 2-arylimidazo[1,2-a]pyridine-3-carbaldehydes with cyclic alpha -diazo-1,3-diketones is presented. To our knowledge, this is the first example in which the title compounds were prepared through Rh(iii)-catalyzed C-H bond carbenoid insertion and [5 + 1] annulation by using cyclic alpha -diazo-1,3-diketones as a C1 synthons featuring with a ring-opening and reannulation. Notably, a wide range of substrates and functional groups were well-tolerated under the optimized reaction conditions to produce products in good to excellent yields.