We have recently reported that 1,2,4-oxadiazole-4-oxides 1 undergo a clean photochemical cleavage 1 to nitriles 2 and nitrosocarbonyls 3, highly reactive intermediates 2 which can be quantitatively trapped with dienes or alkenes to afford the hetero Diels–Alder (HDA) adducts 4 or the ene adducts 5 (Scheme 1). The HDA 3 and ene 4 reactions of nitrosocarbonyls have recently acquired a broad synthetic significance because of the easy manipulation of both ...
