Bromide ion → 5,5'-Dihydroxy-2,2'-diiodobiphenyl

Participants

Reaction Steps

The second 2,2'-dihalo-5,5'-dimethoxybiphenyl, and preferably 2,2'-diiodo-5,5'-dimethoxybiphenyl, is then demethylated under temperatures of about -78° C. to about -20° C., and preferably from about -78° C. to about -50° C., and ambient pressure, with a bromide-containing compound such as hydrogen bromide, boron tribromide, or mixtures thereof in a chlorinated solvent such as a chlorohydrocarbon including but not limited to dichloromethane to yield 2,2'-dihalo-5,5'-dihydroxybiphenyl, and preferably 2,2'-diiodo-5,5'-dihydroxybiphenyl. Boron tribromide is the preferred reactant. The concentration of the bromide-containing compound in the chlorinated solvent may range from 0.05M to about 1M, and preferably from about 0.1M to about 0.5M. The period of the demethylation reaction may depend upon the chemical structure, but will generally be from about 5 minutes to about 2 hours, and preferably from about 15 minutes to about 1 hour. The molar ratio of 2,2'-diiodo-5,5'dimethoxybiphenyl to the bromide-containing compound is about 1:3 to 1:10, and preferably about 1:2.5 to 1:5.

Provenance & Evidence