potassium carbonate; acetone

toluene-4-sulfonic acid in benzene 16 h; Heating;

1: hex-5-ynoic acid With oxalyl dichloride in dichloromethane 2.5 h; Inert atmosphere; 2: With indium(III) chloride in dichloromethane 3 h; Inert atmosphere; 3: phenol in dichloromethane Inert atmosphere;