Oxygen → Allyl m-bromophenyl ether

The compounds of this invention in which X is oxygen are available as in the foregoing, but using a 5-substituted 3-chromanone. This molecule can be produced by a sequence of reactions beginning with m-bromophenol. Briefly, m-bromophenol is treated with allyl bromide in the presence of potassium carbonate to produce allyl 3-bromophenyl ether. The ether is converted to 2-allyl-3-bromophenol upon heating it in the presence of N,N-dimethylaniline. The phenol, upon reaction with ethyl chloroacetate, is converted to the ethyl ester of 2-allyl-3-(carboxymethoxy)bromobenzene. Upon oxidation using ozone followed by reductive work up, the allyl group is converted to a formylmethyl substituent which is then further oxidized using Jones' Reagent to the carboxymethyl substituent, the resulting product being the ethyl ester of (2-carboxymethyl-3-bromo)phenoxyacetic acid. The carboxylic acid group of this compound is esterified with t-butyl acetate and concentrated H2SO4 to form the ethyl ester of 3-bromo-2-(carbo-t-butoxymethyl)phenoxyacetic acid. In the presence of potassium t-butoxide, the diester is cyclized to form 4-t-butoxy-carbonyl-5-bromo-3-chromanone. Upon stirring at room temperature in the presence of acid, the latter is converted to 5-bromo-3-chromanone.