The intramolecular Schmidt reaction of alkyl azides and ketones has been demonstrated. The reaction is proposed to occur via initial attack of an azide on a ketone activated by a variety of protic or Lewis acids, including trifluoroacetic acid, titanium tetrachloride, and others. The resulting azidohydrin undergoes a direct rearrangement to afford the product amide and molecular nitrogen. When cyclic ketones are used, fused bicyclic lactams of types encountered in a wide variety of natural products are obtained. Although the distance allowed between the carbonyl group and the alkyl azide is quite restricted, the reaction is general with respect to the ketone component, including acyclic ketones and cyclic substrates ranging from standard to large ring sizes. The reaction also succeeds with aldehydes, although elimination or hydride migration products compete. In several cases examined, the reaction was found to proceed with retention of configuration at the migrating carbon. Competing reactions with P-diketones and a$-unsaturated ketones were found to predominate over ring expansion. @

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The Lewis acid-promoted reactions of alkyl azides with ketones can afford several products. Chief among these result from a Schmidt-like insertion of the azide into the carbon-carbon bond adjacent to the carbonyl group. Alternatively, an acid-promoted rearrangement of the azide to an iminium species can occur, mostly with benzylic azides; the iminium species can then be trapped by the enol of the carbonyl compound in a variation of the Mannich reaction. The scope of each of these reactions, the dependence of the observed products upon azide and ketone structure, and the nature of acid promotion are discussed. In broad strokes, cyclohexanones and other cyclic ketones react in the presence of TiCl 4 to afford insertion products, whereas the Mannich route predominates when benzyl azide and triflic acid are used. The features that lead to each reaction type and possible mechanistic implications are discussed.

Electrochemistry provides a powerful tool for the late-stage functionalization of complex lactams. A two-stage protocol for converting lactams, many of which are preparable through the intramolecular Schmidt reaction of keto azides, is presented. In the first step, anodic oxidation in MeOH using a repurposed power source provides a convenient route to lactams bearing a methoxy group adjacent to nitrogen. Treatment of these intermediates with a Lewis acid in DCM permits the regeneration of a reactive acyliminium ion that is then reacted with a range of nucleophilic species.

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