Copper-Catalyzed Skeletal Rearrangement of O-Propargylic Alkylaldoximes via N–O Bond Cleavage

Synthesis of Azetidine Nitrones and Exomethylene Oxazolines through a Copper(I)-Catalyzed 2,3-Rearrangement and 4π-Electrocyclization Cascade Strategy

A variety of azetidine nitrones are prepared in moderate to good yields through copper(I) combined with 2-aminopyridine to catalyze skeletal rearrangement of O-propargylic oximes. Mechanistic studies reveal that the reaction undergoes a copper(I)-catalyzed tandem [2,3]-rearrangement, 4π-electrocyclization, ring opening, and recyclization over four steps in one pot. Substituents at the terminus of alkyne and oxime moieties have a significant impact on the formation of azetidine nitrones and exomethylene oxazolines, respectively. Furthermore, the obtained azetidine nitrone could easily participate in [3 + 2] cycloaddition with alkynoates, and a [2.2]-paracyclophane-derived azetidine nitrone is synthesized in 45% yield over five steps from bromo[2.2]-paracyclophane.

Metal-Involving Synthesis and Reactions of Oximes

This review classifies and summarizes the past 10-15 years of advancements in the field of metal-involving (i.e., metal-mediated and metal-catalyzed) reactions of oximes. These reactions are diverse in nature and have been employed for syntheses of oxime-based metal complexes and cage-compounds, oxime functionalizations, and the preparation of new classes of organic species, in particular, a wide variety of heterocyclic systems spanning small 3-membered ring systems to macroheterocycles. This consideration gives a general outlook of reaction routes, mechanisms, and driving forces and underlines the potential of metal-involving conversions of oxime species for application in various fields of chemistry and draws attention to the emerging putative targets.