titanium tetrachloride in dichloromethane T=0°C; 1 h;

1: 3,5-difluoroanisole With n-butyllithium in tetrahydrofuran T=-78°C; 1.5 h; 2: N,N-dimethyl-formamide in tetrahydrofuran T=-78 - 0°C; 0.333333 h;