1: conc.H2SO4 / CH2Cl2 / 120 h / Ambient temperature 2: N2H4*H2O / ethanol / 0.58 h 3: 1.) Ag2CO3, AgClO4, molecular sieve / 1.) CH2Cl2, toluene, 1 h, RT; 2.) 5 d 4: 1.) H2S; 2.) pyridine / 1.) pyridine, H2O, 3.5 h, 0 deg C; 24 h ; 2.) 0 deg C, 24 h 5: 95 percent / HCOOH / 20 h / Ambient temperature View Scheme

1: conc.H2SO4 / CH2Cl2 / 120 h / Ambient temperature 2: N2H4*H2O / ethanol / 0.58 h View Scheme

With  sulfuric acid in  dichloromethane 120 h;  Ambient temperature;