A formal vinylogous Schmidt reaction: nitrogen insertion of para-quinone methides

Abstract

Compared with recent nitrogen addition reactions, which mainly focus on the styrene motif, feasible modification of a conjugated C(sp²)–C(sp²) single bond is rare due to its robustness. Herein, we report a facile nitrogen introduction to the conjugated C(sp²)–C(sp²) bond of p-QMs through a vinylogous Schmidt process, using N-OTs carbamate as a bench-stable ambiphilic nitrogen source. Depending on the electron-donating ability of the ortho-substituent on the benzene ring, the reaction underwent the formal vinylogous Schmidt process through an aziridine intermediate or a 1,6-addition/cyclization step delivering benzoxazolidine or dihydroindazole scaffolds, respectively. This study not only expands the application boundary of the Schmidt reaction but also provides a new strategy for nitrogen addition to a C(sp²)–C(sp²) bond.