Reactions of nitroalkenes with ynamines; synthesis of stable four-membered cyclic nitrones and X-ray crystal structure of 2-(NN-diethylcarbamoyl)-2,4-dimethyl-3-phenyl-2,3-dihydroazete 1-oxide

2,3-Dihydroazete 1-oxides (3b–e), the first examples of crystalline, ‘stable’, four-membered cyclic nitrones, are formed by reaction of 1-nitroalkenes with ynamines, and other products are 3-nitrocyclobutenes; the structure of the cyclic nitrone (3b) has been determined by X-ray crystallography.