INTRODUCING THE DIELS-ALDER REACTIVITY OF 2-FURANMETHANETHIOL WITH SELECTED MALEIC ACID DERIVATIVES

Surprising chemoselectivity is demonstrated in the reaction of 2-furanmethanethiol with maleic anhydride and with N-phenylmaleimide. These maleic acid derivatives demonstrate a predilection for Die Is-Alder cycloaddition, forgoing both conjugate addition and initial carbonyl attack. N-Ethylmaleimide showed a preference for conjugate addition, whereas diethyl fumarate or dimethyl maleate proved unreactive. The cycloadduct of 2-furanmethanethiol and maleic anhydride was subjected to dehydration/aromatization conditions to create benzo[c]thiophen-1(3H)-one-7-carboxylic acid. An alkylation attempt also led to the foimation of a thiolester.