ACID-CATALYZED REARRANGEMENTS OF N-NITROSODEHYDROMORPHOLINE

N-Nitrosodehydromorpholine, a potential metabolic intermediate in the carcinogenic activation of N-nitrosodiethanolamine, and N-nitrosomorph oline, was prepared from the hemiacetal N-nitroso-2-hydroxymorpholine (2) by tosylation and in situ base-catalyzed elimination. The attempte d acid-catalyzed hydration of 3 gives neither 2 nor the unstable alpha -hydroxynitrosamine, N-nitroso-3-hydroxymorpholine (4). The product of this transformation is N-(2-hydroxyethyl)-2-oximinoethanamide (5) as confirmed by an X-ray crystallographic determination. Treatment of 3 w ith gaseous HCl in CH2Cl2 gives 1-aza-4-oxa-3-oximinocyclohexene (6), which rearranges to 5 upon treatment with aqueous acid. The initial re arrangement was proven to be intermolecular by means of a crossover ex periment employing (NO)-N-15 and C-5-D-2 isotopomers of 3.