Reaction of carbethoxynitrene with anthracene, phenanthrene, and pyrene

Abstract

Carbethoxynitrene, generated by thermal decomposition of ethyl azido- formate, reacts with anthracene to yield a mixture of 9-, 1-, and 2-anthrylurethane. Phenanthrene when treated with carbethoxynitrene affords 9-, 1-, and 4-phenanthryl-urethane, and pyrene is similarly converted into a mixture of 1- and 4-pyrenyl- urethane. In any one substrate there is no simple relationship between the isomer ratio and free-valence numbers or bond orders. The relative yields of products are most easily rationalized in terms of a dichotomy of mechanism, the reaction proceeding both by a direct substitution pathway (electrophilic or free-radical) and via an aziridine formed by addition of carbethoxynitrene across positions of high bond order.