1: 5-bromo-2-fluoro-4-methoxybenzaldehyde dimethylacetal in tetrahydrofuran T=-70°C; 0.333333 h; 2: With n-butyllithium in tetrahydrofuran; hexane T=-70°C; 0.166667 h; 3: N,N-dimethyl benzamide With water; toluene-4-sulfonic acid more than 3 stages;