Solvent Free Three-Component Synthesis of 2,4,5-trisubstituted-1H-pyrrol-3-ol-type Compounds from L-tryptophan: DFT-B3LYP Calculations for the Reaction Mechanism and 3H-pyrrol-3-one↔1H-pyrrol-3-ol Tautomeric Equilibrium

Authors :: Ericsson Coy-Barrera
Diego Quiroga
Lili Dahiana Becerra
Source :: Molecules, Vol 25, Iss 4402, p 4402 (2020), Molecules, Volume 25, Issue 19
Publication Year :: 2020
Publisher :: MDPI AG, 2020.
Abstract: In this paper, we describe the solvent-free three-component synthesis of 2,4,5-trisubstituted-1H-pyrrol-3-ol-type compounds from L-tryptophan. The first step of the synthetic methodology involved the esterification of L-tryptophan in excellent yields (93&ndash 98%). Equimolar mixtures of alkyl 2-aminoesters, 1,3-dicarbonyl compounds, and potassium hydroxide (0.1 eq.) were heated under solvent-free conditions. The title compounds were obtained in moderate to good yields (45%&ndash 81%). Density functional theory using &ldquo Becke, 3-parameter, Lee&ndash Yang&ndash Parr&rdquo correlational functional (DFT-B3LYP) calculations were performed to understand the molecular stability of the synthesized compounds and the tautomeric equilibrium from 3H-pyrrol-3-one type intermediates to 1H-pyrrol-3-ol type aromatized rings.

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