The reaction of 2-methyl substituted 1,2-oxazetidin-3-ones (1a, b) wit
h hydrogen chloride affords alpha-chlorocarbohydroxamic acids 3a, b as
intermediates which undergo recyclisation to 1 or elimination to the
atropahydroxamic acid derivative 4. Hydrazines (5) and alkoxyamines (8
) are reacted with 1 b, c to give the alpha-(methyl-aminooxy)carbohydr
azides 6 or alpha-(methylaminooxy)-carbohydroxamic acid derivatives 9
that are smoothly cyclized by 1,1'-carbonyldiimidazole to 1,2,4-oxadia
zi-nan-3,5-diones 7 and 10.