in toluene T=100°C; 2 h;

1: tert-butyl N-[2-(trifluoromethoxy)phenyl]carbamate With tert.-butyl lithium in tetrahydrofuran; pentane T=-78 - -50°C; 1 h; 2: carbon dioxide in tetrahydrofuran; pentane 3: With hydrogenchloride in water pH=1;