Formylation and bromination ortho to the hydroxy-group of 2-carbonyl-substituted phenols in the presence of titanium(IV) chloride

Abstract

Formylation with dichloromethyl methyl ether and titanium(IV) chloride in dichloromethane, and bromination with bromine and titanium(IV) chloride in dichloromethane, of methyl 2,4-dihydroxybenzoate (16), methyl 2-hydroxy-4-methoxybenzoate (17), ethyl 2-hydroxy-4-methoxy-6-methylbenzoate (21), methyl 2-hydroxy-4-methylbenzoate (24), and 2-hydroxy-4- methoxyacetophenone (25) produce appreciable amounts of 3-substituted products. This selective substitution in the position ortho to the hydroxy-group is discussed in terms of a six-membered ring titanium complex. Show more