Volhard–Erdmann cyclization

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Volhard–Erdmann cyclization is a method in organic chemistry for making thiophenes, five-membered rings that contain sulfur. It works by cyclizing 1,4-difunctional compounds (such as disodium succinate, γ-oxo acids, 1,4-diketones, or chloroacetyl-substituted esters) with phosphorus heptasulfide. The reaction is named after Jacob Volhard and Hugo Erdmann. It can produce alkyl- and aryl-substituted thiophenes. An example is the synthesis of 3-methylthiophene from itaconic acid.