1: 93 percent / 4-dimethylaminopyridine / CH2Cl2 / 5 h / Ambient temperature 2: 2,6-lutidine / dimethylformamide / 6 h 3: dimethylformamide / 1 h / 60 °C View Scheme

1: 2,6-lutidine / dimethylformamide / 6 h 2: dimethylformamide / 1 h / 60 °C View Scheme

1: 7.3 g / pyridine / 1.) 5 deg C, 120 h; 2.) r.t., 24 h 2: 93 percent / 4-dimethylaminopyridine / CH2Cl2 / 5 h / Ambient temperature 3: 2,6-lutidine / dimethylformamide / 6 h 4: dimethylformamide / 1 h / 60 °C View Scheme

in N,N-dimethyl-formamide T=60°C; 1 h; Yield given;