Preparation of 4-Hydroxy-2-trifluoromethylthiophene: A Novel Bioisostere of α,α,α-Trifluoro-m-cresol

Abstract

A simple and convenient four-step synthesis of 4-hydroxy-2-trifluoromethylthiophene (1) a novel bioisostere of a,a,atrifluoro-m-cresol is reported. The key step is the condensation between ethyl 3-methoxy-4,4,4-trifluorocrotonate and methyl thioglycolate to form methyl 3-hydroxy-5-trifluoromethylthiophene-2-carboxylate (6). Hydrolysis of the ester followed by decarboxylation furnishes 1. Multi-hundred gram quantities of 1 have been obtained utilizing the present procedure.

Fluorine-containing alkyl(aryl) vinyl sulfides

“…Alkoxycarbonylmethyl polyfluoroalkenyl sulfides containing a functional group in the b-position readily cyclise to thiophenes under the action of bases. 59,127,128 Thus on treatment with sodium methoxide, methoxycarbonylmethyl 1,3,3,3-tetrafluoro-2methoxycarbonylpropenyl sulfide generates a carbanion with participation of the methylene group and undergoes intramolecular cyclisation, which affords 5-fluoro-3-hydroxythiophene 79. The vinylic fluorine atom remains intact.…”

Synthesis of aromatic heterocycles

“…It was then hydrolysed and decarboxylated to 4-hydroxy-2-trifluoromethylthiophene, an isostere of trifluoro-m-cresol. 53 A related route to 3-aminothiophene-2-carboxylic esters bearing a sulfone function at C-4 and a free 5-position has been described. 54 A synthesis of 5-dialkylaminothiophene-2-carboxylic esters from thioamides is illustrated in Scheme 13.…”