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چکیده
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Betti bases, a subclass of amino alcohols, exemplify highly versatile scaffolds in synthetic organic chemistry. These compounds are typically synthesized via a three-component reaction involving β-naphthol, an aromatic aldehyde, and an amine, which provides a robust and efficient route to these multifunctional molecules. When a chiral amine or aldehyde is incorporated as a reactant, the resulting Betti bases exhibit chirality. Alternatively, chiral Betti bases can be obtained by enantiomeric resolution of racemic mixtures using chiral resolving agents. The latter approach is particularly advantageous due to its economic efficiency, circumventing the need for costly enantiomerically pure starting materials while enabling access to single-enantiomer products. Beyond their structural simplicity, chiral Betti bases serve as pivotal intermediates in constructing chiral bioactive molecules and as precursors for diverse chiral ligands integral to catalytic systems for asymmetric transformations. Their utility in enantioselective reactions, such as adding alkyl, alkenyl, and phenyl groups to carbonyl compounds, underscores their importance in synthesizing enantiomerically enriched products essential for pharmaceutical synthesis and fine chemical production, where stereochemical precision is critical [1-3]. Racemic Betti bases were synthesized through a one-pot, three-component reaction involving β-naphthol, pyrrolidine, and benzaldehyde derivatives in ethanol, a green solvent, under reflux conditions. The resulting white-to-yellow solid was washed with ethanol to yield pure racemic Betti bases. The formation of a new stereogenic center was confirmed by the appearance of characteristic signals at approximately 5 ppm and 70 ppm in the ¹H-NMR and ¹³C-NMR spectra, respectively. The chiral Betti bases were obtained by resolving the corresponding racemic mixture using L-(+)-tartaric acid, an inexpensive and environmentally friendly chiral resolving agent. Reaction with L-(+)-tartaric acid generated diastereomeric salts of the (R)- and (S)-enantiomers, which exhibited differential solubility. After filtration, the (S)-(+)-Betti base was obtained from the residue, while the filtrate contained the (R)-(-)-Betti base. Both enantiomers were subsequently purified by treating the salts with sodium carbonate to remove L-(+)-tartaric acid, yielding enantiomerically pure chiral Betti bases.
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