Directed ortho-Metalation and Anionic ortho-Fries Rearrangement of Polycyclic Aromatic O-Carbamates: Regioselective Synthesis of Substituted Chrysenes

Abstract

A general method for the regioselective synthesis of a series of ortho-substituted chrysenyl N,N-diethyl-O-carbamates by the directed ortho-metalation (DoM) strategy is reported. The starting O-carbamates were prepared from the corresponding chrysenols, available by oxidative photochemical cyclization or directed remote metalation tactics. Chrysen-1-yl and chrysene-3-yl ring site selectivity of directed ortho-metalation (DoM) and anionic ortho-Fries rearrangement (AoF) protocols, with s-BuLi/TMEDA, followed by electrophilic quench using a selection of electrophiles, were observed, leading to new chrysenyl derivatives. 5-Chrysenyl N,N-diethyl-O-carbamate underwent instant AoF rearrangement even at −100 °C to furnish chrysenyl o-hydroxycarboxamide. Iterative DoM reactions were carried out to gain insight into the regioselectivity factors.