Direct functionalization of alkyl ethers to construct hemiaminal ether skeletons (HESs)

Hemiaminal ether skeletons (HESs) are important backbones generally found in organic compounds. Compared to traditional functional group transformations, strategies for the C-H functionalization of alkyl ethers to construct HESs have drawn much attention in the past decade. In this review, we focus on the recent progress in developing various pathways to construct HESs via the direct functionalization of alkyl ethers, including: (a) the transition-metal-catalyzed nitrene insertion pathway, (b) the transition-metal-free organonitrenoid insertion pathway, (c) the transition-metal-catalyzed cross-coupling process and (d) the radical-involved cross-coupling pathway under metal-free conditions. In this review, we focus on the recent progress in developing various pathways to construct hemiaminal ether skeletons (HESs) via the direct functionalization of alkyl ethers.