toluene-4-sulfonic acid; orthoformic acid triethyl ester in 1,2-dichloro-ethane T=80°C; 2.5 h;

toluene-4-sulfonic acid in ethylene glycol; toluene

1: With n-butyllithium in tetrahydrofuran; hexane 0.666667 h; Cooling with acetone-dry ice; 2: With iodine in tetrahydrofuran; hexane T=5°C; 2.16667 h; Cooling with acetone-dry ice; 3: With sodium thiosulfate in tetrahydrofuran; hexane; ethyl acetate T=5°C; 0.0833333 h;