SYNTHESIS OF 4-FLUORORESORCINOL AND 4-TRIFLUOROMETHYLRESORCINOL

Less expensive, safer, and easily scaled-up methods for the synthesis of 4-fluororesorcinol and 4-trifluoromethylresorcinol have been establ ished including two methods to give the former compound. One involves the reaction of Selectfluor(TM) reagent with 1,3-dimethoxybenzene to g ive 2,4-dimethoxy-1-fluorobenzene followed by hydrolysis to give 4-flu ororesorcinol. The overall yield of this two-step reaction is 54%. In the second case, when Selectfluor reagent is reacted directly with res orcinol, under the best reaction conditions, 4-fluororesorcinol is obt ained in 66% yield. It is, however very difficult to separate the star ting material from the mono- and difluororesorcinol products. Conseque ntly, the two-step method is the method of choice to prepare 4-fluoror esorcinol. The trifluoromethyl group was incorporated into 2,4-dimetho xy-1-iodobenzene to form 1,3-dimethoxy-4-trifluoromethylbenzene follow ed by mild hydrolysis to give 4-trifluoromethylresorcinol. (C) 1998 Jo hn Wiley & Sons, Inc.