@article { ISI:000381052600004,
	title = {Crystal structure, computational studies, and stereoselectivity in the synthesis of 2-aryl-thiazolidine-4-carboxylic acids via insitu imine intermediate},
	journal = {Journal of Sulfur Chemistry},
	volume = {37},
	number = {4},
	year = {2016},
	month = {MAR},
	pages = {401-425},
	publisher = {TAYLOR \& FRANCIS LTD},
	address = {2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLAND},
	abstract = {<p>This article presents the synthesis of (2R/2S,4R)-2-aryl-thiazolidine-4-carboxylic acids via nucleophilic addition of L-Cysteine on aromatic aldehydes involving a yield and time-effective room temperature reaction in an aqueous DMSO medium in the presence of NaHCO3 as a base. The synthesized diastereomers were spectroscopically characterized and quantified for diastereomeric excess by liquid chromatography-mass spectrometry analysis. The impact of the type and position of substituent in aromatic aldehydes on reaction time, \% yield, H-1 NMR shift at newly formed chiral center [C(2)-H], and diastereomeric excess (de\%) have been investigated. A plausible mechanism for stereoselectivity via an in situ imine intermediate is proposed using real-time IR monitoring of the synthetic reaction based on the significant signals at 1597, 1593cm(-1) for imine (C=N) stretching. The imine mechanism for stereoselectivity was further supported by NMR studies of azomethine C-13 NMR signals at 159, 160ppm and by the single crystal structure of hitherto unknown (2S,4R)-3-(tert-butoxycarbonyl)-2-(2-hydroxyphenyl)thiazolidine-4-carbox ylic acid (3a) obtained as a major diastereomer in the synthesis of the butyloxy carbonyl (BOC) derivative of (2R/2S,4R)-2-(2-hydroxyphenyl)thiazolidine-4-carboxylic acid. The significant ortho-OH effect of phenolic hydroxyl group leading to strong hydrogen bondings plays a vital role in the formation of 2S,4R BOC derivative stereoselectively. The frontier molecular orbitals, possible electronic excitations, IR band characterizations, and reactivity parameters of newly reported compound (3a) have been predicted using quantum chemical descriptors from density functional theory. The theoretical exploration of experimental spectra using time-dependent DFT indicated a (-*) transition between HOMO and LUMO in the ultraviolet region.</p>},
	keywords = {2-aryl-thiazolidine-4-carboxylic acids, density function theory, frontier molecular orbitals, imine intermediate, X-ray crystal structure},
	issn = {1741-5993},
	doi = {10.1080/17415993.2016.1156116},
	author = {Jagtap, Rohidas M. and Rizvi, Masood A. and Dangat, Yuvraj B. and Pardeshi, Satish K.}
}
@article {49549,
	title = {Optimization and mechanistic insights of zinc ascorbate catalyst for ring-opening polymerization of caprolactone using RSM methodology and DFT calculations},
	journal = {Polymers for Advanced Technologies},
	volume = {36},
	year = {2025},
	month = {APR},
	pages = {e70182},
	type = {Article},
	abstract = {<p>
	Polycaprolactone (PCL) is an aliphatic polyester recognized for its exceptional versatility and biodegradability, which has garnered significant attention for a wide range of applications. This study presents an innovative methodology for the synthesis of PCL through the ring-opening polymerization (ROP) of epsilon-caprolactone (CL). The approach employs a biocompatible and environmentally benign organometallic zinc ascorbate complex as a catalyst. Derived from ascorbic acid, a well-established reducing agent, zinc ascorbate serves as a sustainable alternative to conventional tin-based catalysts, thereby mitigating environmental impact and enhancing safety measures. The catalyst operates effectively under solvent-free conditions and does not require initiators, achieving a high polymer conversion rate of approximately 79\%. The optimization of the reaction parameters was conducted using response surface methodology (RSM) employing a central composite design (CCD). The structural and chemical characterization of the catalyst as well as the resulting polymers was performed using proton nuclear magnetic resonance (1H NMR), Fourier-transform infrared spectroscopy (FTIR), and x-ray diffraction (XRD) analyses. Additionally, density functional theory (DFT) calculations elucidated a four-step coordination-insertion mechanism for the polymerization of cyclic lactones, with findings supported by Gibbs free energy, electrostatic potential, and non-covalent interactions. This study underscores the potential of zinc ascorbate as a reliable, nontoxic, and cost-effective catalyst, fulfilling the increasing demand for sustainable and efficient polymerization processes in commercial and biomedical applications.</p>
},
	keywords = {density function theory, Polycaprolactone, Response surface methodology, ring-opening polymerization, zinc ascorbate},
	issn = {1042-7147},
	doi = {10.1002/pat.70182},
	author = {Naik, Sonali S. and Vedpathak, Shantanu and Nair, Kiran Sukumaran}
}
