Access to benzo[e][1,3]thiazin-4-ones via PCy3-mediated annulations of benzo[c][1,2]dithiol-3-ones with iso(thio)cyanates

Abstract

Herein, we describe a novel organophosphine-mediated annulation reaction of benzo[c][1,2]dithiol-3-ones with iso(thio)cyanates, which proceeds via an S atom to C–N unit exchange strategy. The methodology efficiently produces a variety of benzo[c][1,2]dithiol-3-one derivatives in moderate to excellent yields under straightforward reaction conditions. Other salient features of this approach include transition-metal-free process, operational simplicity, gram-scale synthesis, and capacity for late-stage modifications. Additionally, control experiments were conducted to provide new insights into the conversion mechanism of benzo[c][1,2]dithiol-3-ones.