1: thien-2-yl bromide With hydrogenchloride; iodine; magnesium; triethylamine in tetrahydrofuran 2 h; Heating / reflux; 2: With sulfur in tetrahydrofuran T=45 - 50°C; 2 h; 3: trans-crotonic acid With hydrogenchloride; triethyl amine hydrochloride; triethylamine more than 3 stages;

triethylamine in toluene T=15°C; Reflux;

1: With oxalyl dichloride in dichloromethane; N,N-dimethyl-formamide T=20°C; 2 h; 2: With tin(ll) chloride in dichloromethane; N,N-dimethyl-formamide T=0 - 5°C;