Figure 2

Reaction conditions: (a) dry acetone, K₂CO₃; (b) metallic sulfur, glycerol/K₂CO₃ (10:1 (ml/mmol)), 80 °C; (c) dry xylene, reflux; (d) EtOH, reflux; (e) EtOH, reflux; (f) THF, rt; (g) glacial CH₃COOH or NH₄Cl, reflux; and (h) glacial CH₃COOH, reflux.