Single‐Step Modular Synthesis of Unsaturated Morpholine N ‐Oxides and Their Cycloaddition Reactions

A single‐flask procedure for the generation of α‐keto‐ N ‐alkenylnitrones through a Chan–Lam coupling and subsequent spontaneous 6π electrocyclization of these intermediates for the synthesis of 2 H ‐1,4‐oxazine N ‐oxides has been developed for a variety of α‐ketooximes and alkenylboronic acids. This transformation provides a new approach to C‐substituted unsaturated morpholine derivatives that are poised to undergo further functionalization for the preparation of a diverse array of novel heterocyclic structures. The scope of the new method for the synthesis of 2 H ‐1,4‐oxazine N ‐oxides is discussed, in addition to initial studies describing the cycloaddition reactivity of these new heterocyclic intermediates.