lithium hexamethyldisilazane in tetrahydrofuran; cyclohexane T=-78°C;

1: pyrrolidin-2-one; di-tert-butyl dicarbonate With 4-(N,N-dimethlyamino)pyridine in dichloromethane T=20°C; 2: carbonic acid dimethyl ester With lithium hexamethyldisilazane in dichloromethane T=-78°C;