Preparation of 2‐substituted 1,3,4‐thiadiazoles and mesoionic 1,3,4‐thiadiazole[3,2‐c]quinazolines from 4H‐3,1‐benzothiazine‐4‐thiones or 3‐amino‐4(3H)‐quinazolinethiones | Publicación