4-(N,N-dimethlyamino)pyridine in tetrahydrofuran T=0 - 20°C; 2 h;

1: in chloroform T=0°C; 0.5 h; 2: With 4-(N,N-dimethlyamino)pyridine; dicyclohexyl-carbodiimide in chloroform T=0 - 20°C; 20 h;