Progress in the Research of Copper Promoted C—H Functionalizations for the Synthesis of Fused Heterocycles Bearing Bridgehead Nitrogen

Abstract

The copper-catalyzed C—H activation, selective functionalization and the development of cyclization strategy for the synthesis of novel fused-heterocyclic (heterocycles with ring-junction nitrogen or bridgehead nitrogen) compounds are discussed. This class of novel bridgehead nitrogen heterocycles includes indolizine, pyrazolopyridine, benzimidazole and other polyheterocyclic compounds. The series including modern amination, oxidative coupling and Csp2—H, Csp—H, Csp3—H and N—H activation catalyzed by Cu(I) or Cu(II) salts makes this green synthesis a superior and practical method providing entry into complex heterocycles. Some reaction mechanisms have also been summarized. Keywords copper-catalyzed; bridgehead nitrogen fused-heterocycles; oxidative coupling; C—H activation; N—H activation, cyclization; annulation