*Article* **Unexpected Decarbonylation of Acylethynylpyrroles under the Action of Cyanomethyl Carbanion: A Robust Access to Ethynylpyrroles**

**Denis N. Tomilin 1, Lyubov N. Sobenina 1, Alexandra M. Belogolova 1,2, Alexander B. Trofimov 1,3, Igor A. Ushakov <sup>1</sup> and Boris A. Trofimov 1,\***


**Abstract:** It has been found that the addition of CH2CN− anion to the carbonyl group of acylethynylp yrroles, generated from acetonitrile and *t*-BuOK, results in the formation of acetylenic alcohols, which undergo unexpectedly easy (room temperature) decomposition to ethynylpyrroles and cyanomethylp henylketones (*retro*-Favorsky reaction). This finding allows a robust synthesis of ethynylpyrroles in up to 95% yields to be developed. Since acylethynylpyrroles became available, the strategy thus found makes ethynylpyrroles more accessible than earlier. The quantum-chemical calculations (B2PLYP/6-311G\*\*//B3LYP/6-311G\*\*+C-PCM/acetonitrile) confirm the thermodynamic preference of the decomposition of the intermediate acetylenic alcohols to free ethynylpyrroles rather than their potassium derivatives.

**Keywords:** acylethynylpyrroles; alkynones; terminal alkynes; deacylation; *retro*-Favorsky reaction
