Synthesis of 3-dialkylaminochromans via thallium(III)-induced cyclization of allyl aryl ethers

The sulfur-containing 3-alkylaminochromans, 5-methoxy-3-[N-(2- methylthioethyl)-propylamino]chroman (15), 5-hydroxy-3-[N-(2-methylthioethyl)propylamino]chroman (5) and 5-methoxy-8-methylthio-3-(dipropylamino)chroman (6), have been prepared from 8-bromo-5-methoxy-3-chromanol (11). This precursor was synthesized from 3-allyloxy-4-bromoanisole (8), by a thallium(III)-mediated ring-closure reaction. Compound 11 also served as starting material for the synthesis of 8-bromo-3-(dipropylamino)-5-methoxychroman (7).