Chemistry of polyenic and polyacetylenic compounds Communication 10. Condensation of 5-bromo-3,4-dimethyl-3-penten-1-yne with sodiomalonic ester

Abstract

1. In the condensation of the primary enynic bromo compound (I) with sodiomalonic ester the malonic-synthesis reaction is accompanied by intramolecular nucleophilic addition at the acetylene bond with formation of diethyl 3,4-dimethyl-2-methylene-3-cyclopentene-1,1-dicarboxylate, which gives 2,3,4-trimethyl-1,3-cyclopentadiene-1-carboxylic acid on alkaline hydrolysis. 2. The structures of the substances formed were proved with the aid of their spectra and chemical reactions. 3. The condensation of the bromo compound (I) with the sodium derivative of methylmalonic ester was studied, and it was shown that in this case the reaction goes in accordance with the usual malonic-synthesis scheme.