The Volhard–Erdmann cyclization is an organic synthesis of alkyl and aryl thiophenes by cyclization of disodium succinate or other 1,4-difunctional compounds (γ-oxo acids, 1,4-diketones, chloroacetyl-substituted esters) with phosphorus heptasulfide. The reaction is named after Jacob Volhard and Hugo Erdmann. An example is the synthesis of 3-methylthiophene starting from itaconic acid:
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