1: 2,2,4,4-tetramethyl-3-thioxocyclobutanone S-oxide With Lawesson's reagent in dichloromethane T=20°C; 0.166667 h; 2: 2,2,4,4-tetramethyl-3-thioxocyclobutan-1-one in dichloromethane T=20°C; 168 h;