A facile synthesis of 7-chloromethyl-1H-indole-2-carboxylates : Replacement of a sulfonic acid functionality by chlorine

Valuable new synthetic intermediates, 7-chloromethyl-1H-indole-2-carboxylates (3a-d), were prepared by the facile elimination of sulfur dioxide under the influence of thionyl chloride from 2-ethoxycarbonyl-1H-indole-7-methanesulfonic acids (1a-d), easily accessible by Fischer-type indolisation. The 7-chloromethylindoles easily underwent methanolysis and aminolysis.