Effects of tertiary amine catalysis on the regioselectivity of anisole chlorination with trichloroisocyanuric acid

Tertiary amines and their salts in dichloromethane were found to induce a strong para regioselectivity in the chlorination of anisole as the model substrate with trichloroisocyanuric acid (TCCA). Using a catalyst loading of 6 mol % trimethylammonium chloride gave a para vs. ortho selectivity of 38:1. This effect is attributed to the in situ formation of N-chlorotrialkylammonium salts, which chlorinate alkyl aryl ethers with a high regioselectivity. The regioselectivity and monochlorination selectivity for anisole chlorination with TCCA in numerous solvents are reported. The chlorination of a few related benzenoid substrates under selected conditions is described.