Highly regioselective halogenation of 1-phenyl-3-(3,5-dimethoxyphenyl)-propane-1,3-dione

Halogenation of 1-phenyl-3-(3,5-dimethoxyphenyl)-propane-1,3-dione (1) with N–X reagents take place regioselectively at the α position (except for fluorination), while halogenation of its BF2 derivative 3 take place regioselectively at position 2 in the activated phenyl ring. When the molar ratio of substrate to reagent is changed from 1:1.1 to 1:2.1 or 1:2.8, halogenation takes place at positions 2 and 6 of the aromatic ring. Crystallization of a BF2 derivative from protic solvent led to hydrolysis of the BF2 group.