Abstract A one-flask conversion of cyclic ketones to N-methyl lactams is described. Reaction of the ketone with triethylorthoformate generates an acetal which is reacted in situ with N-(((p- nitrobenzene) sulfonyl) oxy methylamine 2a (CH 3 NH-OSO 2 C 6 H 4 NO 2). Dealkylation of the resulting O-ethyl imidate with sodium iodide gives the lactam. A variety of lactams, including macrocyclic lactams, are produced simply and in good yields.