A one-pot methods were developed for the synthesis of five-membered sulfur and selenium heterocycles based on the consecutive cyclometallation of olefins, allenes, and acetylenes using alkyl and haloalkyl derivatives of Al and Mg in the presence of catalytic amounts of titanium and zirconium complexes to give the corresponding alumina-and magnesacarbocycles in situ, which, without further purification, were introduced into reaction with sulfur or selenium, leading to various tetrahydrothiophenes, thiophenes, tetrahydroselenophenes, and selenophenes.Thiophene is separated from the coking products of mineral coal or obtained by the thermal reaction of C 4 -hydrocarbons with sulfur, hydrogen sulfide, and SO 2 [1-3]. One of the most popular synthetic methods for the preparation of tetrahydrothiophenes and selenophenes is a method based on use of the Yur'ev reaction [4,5].Along with these methods, the synthesis of five-membered heterocycles by means of replacing transition metal atoms, in particular, the zirconium atom in zirconacyclopentanes, zirconacyclopentenes, and zirconacyclopentadienes by sulfur and selenium atoms, has been found feasible [6][7][8][9]. Unfortunately, this method has not found common use due to the need to employ stoichiometric amounts of the zirconacycloalkanes and the difficulty in preparing these organometallic precursors.The reactions of metallacycloalkanes, prepared in situ using nontransition metals, aluminacyclopentanes [10-12], magnesacyclopentanes [13,14], and their derivatives prepared in situ by the Dzhemilev reaction by means of the catalytic cycloalumination and cyclomagnesation of unsaturated compounds using alkyl Mg and Al derivatives by the action of catalysts derived from Ti and Zr complexes, with S 8 and Se hold promise for the synthesis of five-membered heterocycles (Scheme 1). _______ * Dedicated to Academician B. A. Trofimov of the Russian Academy of Sciences on the occasion of his seventieth jubilee.