The Reaction of 3,4-Dinitrothiophene with Grignard Reagents: Formation of 2-(3-Amino-4-nitrothiophen-2-yl)phenols

The treatment of 3,4-dinitrothiophene with an aryl Grignard reagent results in the reduction of one nitro group accompanied by the ipso-substitution of a hydrogen atom by an ortho-phenolic group on the ring carbon adjacent to the reduced nitro group. A Claisen-type intramolecular rearrangement is proposed as the pivotal step of a rather complex mechanism, followed by proton-transfer aromatizing steps. This work shows yet another facet of the variegated reactivity of 3,4-dinitrothiophene towards nucleophiles. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)