in dichloromethane Irradiation (UV/VIS); under Ar, irradn. for 30 min; solvent was removed, chromy. (silica, n-hexane-CH2Cl2 (3:1, v/v));

in chloroform under Ar, carbonylation, 0.5 h, room temp.; solvent was removed in vac., chromy. (silica, n-hexane-CH2Cl2 (3:1, v/v));