Nitrene insertion reactions. 1. Dimethyl N-carbethoxyazepines and their cycloaddition reaction products

Dimethyl-N-carbethoxyazepines, isolated from the reaction between ethyl azidoformate and o-, m- and p-xylenes, react with tetracyanoethylene to give 4 + 2] Diels-Alder adducts. Nitroso-benzene is inert toward 2-methylazepines, but reacts with 3,6-dimethyl-N-carbethoxyazepine to give a 6 + 2] cycloadduct. The effect of two methyl substituents on the course of the cycloaddition reactions is discussed.