Reactions of alkyl azides and ketones as mediated by Lewis acids: Schmidt and Mannich reactions using azide precursors

Citation
P. Desai et al., Reactions of alkyl azides and ketones as mediated by Lewis acids: Schmidt and Mannich reactions using azide precursors, J AM CHEM S, 122(30), 2000, pp. 7226-7232
Citations number
36
Categorie Soggetti
Chemistry & Analysis",Chemistry
Journal title
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
ISSN journal
00027863 → ACNP
Volume
122
Issue
30
Year of publication
2000
Pages
7226 - 7232
Database
ISI
SICI code
0002-7863(20000802)122:30<7226:ROAAAK>2.0.ZU;2-4
Abstract
The Lewis acid-promoted reactions of alkyl azides with ketones can afford s everal products. Chief among these result from a Schmidt-like insertion of the azide into the carbon-carbon bond adjacent to the carbonyl group. Alter natively, an acid-promoted rearrangement of the azide to an iminium species can occur, mostly with benzylic azides; the iminium species can then be tr apped by the enol of the carbonyl compound in a variation of the Mannich re action. The scope of each of these reactions, the dependence of the observe d products upon azide and ketone structure, and the nature of acid promotio n are discussed. In broad strokes, cyclohexanones and other cyclic ketones react in the presence of TiCl4 to afford insertion products, whereas the Ma nnich route predominates when benzyl azide and triflic acid are used. The f eatures that lead to each reaction type and possible mechanistic implicatio ns are discussed.