Synthesis of Benzo[e][1,3]thiazin‐4‐ones via PPh₃‐Promoted Cyclization of Benzo[c][1,2]dithiol‐3‐ones and Amidines

A phosphine‐mediated cyclization of benzo[c][1,2]dithiol‐3‐ones and amidines is demonstrated herein. Triphenylphosphine was harnessed as the activating reagent to facilitate the ring‐opening of benzo[c][1,2]dithiol‐3‐ones via S−S bond cleavage. This PPh 3 ‐Promoted cyclization reaction of benzo[c][1,2]dithiol‐3‐ones enabled to forge a diverse array of 1,3‐benzothiazones in decent yields with wide substrate scope under mild conditions.