BENZYLATION OF THIOPHENE USING ZINC AND IRON CHLORIDE MODIFIED MONTMORILLINITE CLAY

Montmorillinite clays, modified with either Zn(II) or Fe(III) chloride s have been used to catalyze the Friedel-Crafts alkylation of thiophen e. High yields (ca. 80%) of 2- and 3-benzylthiophene mixtures were obt ained using either catalyst in chlorobenzene or nitrobenzene solvent a t 80-degrees-C. The ratio of 2-/ 3-products was found to be controlled by their relative stability. Reactions were most rapid in nitrobenzen e solution (< 5 min) and resulted in formation of the 2-isomer as the only mono-substituted product. This is believed to be the first exampl e in which an alkylation of thiophene has been limited to one regio-is omer.