A Quantum Chemical Study on the Mechanisms of Acylpyrrolylacetylenes Reactions With 1-Pyrrolines

The mechanisms of reactions between electron-deficient acetylenes, specifically acylpyrrolylacetylenes, and 1-pyrrolines were examined using a DFT B2PLYP-D3/6-311++G**//B3LYP/6-31+G* approach. The study was focused on the interaction of 1-phenyl-3-(1H-pyrrol-2-yl) prop-2-yn-1-one with 5-methyl-3,4-dihydro-2H-pyrrole, and was aimed at a clearer understanding of the reaction progress. The reaction pathway for the synthesis of a dipyrroloimidazole derivative comprising three five-membered nitrogen-containing heterocycles is compared to one typical for N-substituted acylethynylpyrroles, which involves opening the pyrroline ring to form delta-keto aminoenones. An explanation is presented for the high level of deuterium exchange during the reaction in deuterated methanol. Also, the impact of trace water in acetonitrile was assessed. A ring-opening mechanism is proposed, involving the 1-pyrroline molecule as a base. The photochemical isomerization process of the end product is also examined. The mechanisms of reactions between electron-deficient acetylenes, specifically acylpyrrolylacetylenes, and 1-pyrrolines were examined using a DFT B2PLYP-D3/6-311++G**//B3LYP/6-31+G* approach. The reaction pathway for the synthesis of a dipyrroloimidazole derivative comprising three five-membered nitrogen-containing heterocycles is compared to one typical for N-substituted acylethynylpyrroles, which involves opening the pyrroline ring to form delta-keto aminoenones.image