Ring expansion by in situ tethering of hydroxy azides to ketones: The Boyer reaction

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 attack of azide on an oxonium ion intramolecular. The scope of this reaction vis a vis ketone and hydroxyalkyl azide structure is discussed. (C) 1997 Elsevier Science Ltd.