**Lyubov' N. Sobenina and Boris A. Trofimov \***

A.E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch, Russian Academy of Sciences, 1 Favorsky Str., 664033 Irkutsk, Russia; sobenina@irioch.irk.ru

**\*** Correspondence: boris\_trofimov@irioch.irk.ru; Tel.: +7-(3952)41-93-46

Academic Editors: José Pérez Sestelo and Luis A. Sarandeses Received: 25 April 2020; Accepted: 25 May 2020; Published: 27 May 2020

**Abstract:** The publications covering new, transition metal-free cross-coupling reactions of pyrroles with electrophilic haloacetylenes in solid medium of metal oxides and salts to regioselectively afford 2-ethynylpyrroles are discussed. The reactions proceed at room temperature without catalyst and base under solvent-free conditions. These ethynylation reactions seem to be particularly important, since the common Sonogashira coupling does not allow ethynylpyrroles with strong electron-withdrawing substituents at the acetylenic fragments to be synthesized. The results on the behavior of furans, thiophenes, and pyrazoles under the conditions of these reactions are also provided. The reactivity and structural peculiarities of nucleophilic addition to the activated acetylene moiety of the novel C-ethynylpyrroles are considered.

**Keywords:** electrophilic haloacetylenes; pyrroles; ethynylpyrroles; furans; thiophenes; pyrazoles; Al2O3
