1: 72 percent / pyridine, AgNO3 / tetrahydrofuran / 2.5 h / Ambient temperature 2: 75 percent / 4-dimethylaminopyridine / acetonitrile / 5 h / Ambient temperature 3: 90 percent / tributyltin hydride, 2,2'-azobis (2-methylpropionitrile) / benzene / 1.33 h / Heating 4: 88 percent / 80percent aq. HOAc / 3.25 h / Ambient temperature View Scheme