For the first time, regio- and stereoselective synthesis of tetraalkyl-substituted buta-1,3-dienes was carried out using the reaction of dialkyl-substituted alkynes with EtAlCl₂ and metallic magnesium in the presence of catalytic amounts of tantalum (V) chloride in a toluene solution. The effect of the nature of the solvent and temperature on the process of oxidative coupling of molecules of disubstituted alkynes on low-valent tantalum has been studied. A scheme is proposed for the catalytic conversion of disubstituted alkynes to buta-1,3-dienes under the conditions of organoaluminum synthesis. It was found that the reaction of in situ obtained metallocyclopentadienes with methanesulfonyl chloride leads to the selective formation of tetraalkyl-substituted 1,4-dichlorobuta-1,3-dienes.