water; propionic acid T=140°C; P=52476.2 Torr; 2 h; Autoclave;

sulfuric acid Reflux;

1: propionic acid With hydrogen sulfide; triethylamine; isobutyl chloroformate in dichloromethane T=-15°C; 4.5 h; Cooling with ethylene glycol dry ice; 2: propionyloxymethyl chloride With triethylamine in DMF (N,N-dimethyl-formamide) T=20°C; 60 h;