Recent Advances in Annulation Reactions of α,β-Unsaturated Ketoximes for the Synthesis of Structurally Diversified Heterocycles

Transition metal-catalyzed or metal-free-mediated annulation of α,β-unsaturated ketoximes with unsaturated coupling partners has emerged as a powerful protocol for the assembly of diverse functionalized heterocycles, which is attributed to the ability of the oxime functionality to serve as a directing group for C−H activation, to undergo reductive N−O bond cleavage, and be activated by Lewis acids or reduced by iodide salt. In this review, we summarize the coupling reactions of three types of α,β-unsaturated ketoximes with various organic compounds containing unsaturated bonds such as alkenes, alkynes, carbonyls, nitriles and so on over the past decades. The reaction conditions, selected examples of the reaction scope, limitations, and reasonable mechanisms are critically described. Furthermore, the prospects for future challenges and opportunities are also explored.