Abstract N-Acylnitroso derivatives 6 which were prepared by in-situ oxidation of the corresponding hydroxamic acids 5 reacted instantaneously and in high yields with dihydropyridine 4. The Diels-Alder adducts 8 were formed regiospecifically with the acylnitroso dienophiles 6a–c, whereas the dienophiles 6d–f gave mixtures of both regioisomers 7 and 8. These and some other results [2] were best explained by the FMO ...
