1: With n-butyllithium in tetrahydrofuran; hexane T=5 - 20°C; 1 h; 2: With boric acid trimethyl ester in tetrahydrofuran; hexane T=-70°C; 0.5 h; 3: With ammonium chloride in tetrahydrofuran; hexane T=-15 - 20°C; 1 h;