Cp2TiCl2-catalyzed reaction of symmetrical alkynes with aα,ω-dicarboxylic acid esters and EtAlCl2: An original pathway to C5-C6 cyclic ketones and tetrasubstituted furans

An original method for the synthesis of C5-C6 cyclic ketones and tetrasubstituted furans was developed based on the Cp2TiCl2-catalyzed reaction of symmetrical alkynes and alpha,omega-dicarboxylates in the presence of Mg and EtAlCl2. The length of the hydrocarbon chain between carboxyl groups in a,omega-dicarboxylic acid esters affects the chemoselectivity of the reaction. The formation of 2-alkylidene and 2-alkenyl cyclopent(hex)an-l-ones occurred in the reaction with esters of glutaric and adipic acids. alpha,omega-Dicarboxylic acid esters with more than four methylene units between carboxyl groups gave rise to substituted furans. Stereochemistry of 2-alkenyl cydopent(hex)an-l-ones was determined based on the analysis of experimental and theoretical data obtained from DFT calculations. (C) 2018 Elsevier Ltd. All rights reserved.