sulfuric acid; magnesium sulfate in dichloromethane T=20°C; 48 h;

1: 2,5-dibromothiophene With n-butyllithium; n-butyl-magnesium chloride in tetrahydrofuran; hexane; toluene T=-10°C; 2: di-tert-butyl dicarbonate in tetrahydrofuran; hexane; toluene T=-10°C; 3: With citric acid in tetrahydrofuran; hexane; toluene Further stages.;

tert-butyl alcohol