The oxa-Michael reaction in the synthesis of 5-and 6-membered oxygen-containing heterocycles

The oxa-Michael reaction (OMR) offers the most effective and straightforward route to the synthesis of a wide range of 5- and 6-membered oxygen-containing heterocycles including tetrahydropyrans, tetrahydrofurans, 1,4 dioxanes, isoxazolidines, isoxazolines, gamma-lactones and related gamma-butenolides. These molecular frameworks are frequently featured in numerous biologically active substances. Moreover, the emergence of organocatalytic asymmetric OMR has empowered access to a variety of diverse oxygen-containing heterocycles in a highly enantio- and/or diastereoselective fashion. This review provides an updated account on the recent advances and applications of OMR in the synthesis 5- and 6-membered monocyclic oxo-heterocycles published in the literature since 2013 to date.