1: 68 percent / H2S / dimethylformamide / 1.5 h / -5 °C 2: anhydrous K2CO3 / acetone / 20 h / 20 °C 3: 61 percent / NEt3 / benzene / 5 h / Heating 4: 87 percent / Bu3SnH; α,α'-azoisobutyronitrile / benzene / 2 h / Heating 5: 89 percent / H2 / 10 percent Pd/C / methanol View Scheme

hydrogen sulfide in N,N-dimethyl-formamide T=-5°C; 1.5 h;

1: 68 percent / H2S / dimethylformamide / 1.5 h / -5 °C 2: anhydrous K2CO3 / acetone / 20 h / 20 °C 3: 61 percent / NEt3 / benzene / 5 h / Heating 4: 87 percent / Bu3SnH; α,α'-azoisobutyronitrile / benzene / 2 h / Heating View Scheme