Although alkyl azides can react with ketones to form ring-expanded lactams, the reaction suffers from poor generality and the need to use powerful Lewis acid promotion. The reactions of 1, 2-and 1, 3-hydroxyalkyl azides with ketones yield N-hydroxyalkyl lactams in high yields under the action of protic or Lewis acids such as BF3· OEt2. The reaction appears to succeed due to the initial formation of a hemiketal, which then renders the ...