Reactions of Ethyl Diazoacetate with Thianaphthene, Indoles, and Benzofuran

The thermolysis of ethyl diazoacetate in thianaphthene leads in low yield to the heterocycle's 3-acetic ester and 2,3-cyclopropanation products. Copper catalysis furnishes the same products along with triethyl 1,2,3-cyclopropanetricarboxylate. Copper-induced thermolysis of the diazo ester in 1,3-dimethylindole produces in low yield ethyl 1,3-dimethyl-2-indolylacetate, whereas the reaction on N-acylindoles leads to the trapping of the enamine double bond in the form of cyclopropane esters. A similar reaction of benzofuran yields cyclopropane carboxylates, whose acid-catalyzed ring opening yields 2- and 3-benzofuranacetic esters. In aqueous acid a major product is o-(β- carboxypropionyl)phenol. Acid-induced opening of carbinol reduction products of the cyclopropane esters give 2- and 3-vinylbenzofurans.