Efforts towards Rh(II)-catalyzed N-alkoxyazomethine ylide generation: Disparate reactivities of O-tethered α-diazo keto and -β-ketoester oximes

Abstract Azomethine ylide [3 + 2] cycloaddition reactions are among the most powerful and well-studied chemical transformations to construct five-membered nitrogen-containing frameworks. However, cycloadditions of azomethine ylides bearing N-alkoxy substituents have largely been overlooked. This has been the case despite the potential for (1) accessing heterocycles with good regio- and diastereocontrol, (2) the presence of a cleavable tether which can be manipulated downstream via N–O bond cleavage, and (3) the promise of interesting structural diversity. Herein, we describe our efforts toward dirhodium-catalyzed intramolecular N-alkoxyazomethine ylide generation from α-diazo keto and -β-ketoester oximes and the disparate reactivities observed.