1: 82 percent / CH2Cl2 / 2 h / Ambient temperature 2: 83 percent / 0.5 h / 0 °C / Irradiation; diphenyl disulphide or diselenide or var. aromatic ditellurides, var. derivatives of alifatic or alicyclic carboxylic acids and and N-hydroxy-2-thiopyridone, var. rection times View Scheme

T=0°C; 0.5 h; Irradiation;