02892nas a2200241   4500008004100000022001400041245015700055210006900212260009400281300001200375490000700387520187800394653004302272653002802315653003202343653002302375653002802398100002402426700002202450700002302472700002502495856013002520       2016                        eng d  a1741-599300aCrystal structure, computational studies, and stereoselectivity in the synthesis of 2-aryl-thiazolidine-4-carboxylic acids via insitu imine intermediate0 aCrystal structure computational studies and stereoselectivity in  a2-4 PARK SQUARE, MILTON PARK, ABINGDON OR14 4RN, OXON, ENGLANDbTAYLOR & FRANCIS LTDcMAR  a401-4250 v373 a<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>10a2-aryl-thiazolidine-4-carboxylic acids10adensity function theory10afrontier molecular orbitals10aimine intermediate10aX-ray crystal structure1 aJagtap, Rohidas, M.1 aRizvi, Masood, A.1 aDangat, Yuvraj, B.1 aPardeshi, Satish, K.  uhttp://library.ncl.res.in/content/crystal-structure-computational-studies-and-stereoselectivity-synthesis-2-aryl-thiazolidine02612nas a2200229   4500008004100000022001400041245016000055210006900215260000800284300001100292490000700303520173900310653002802049653002102077653003302098653003202131653001902163100002102182700002402203700002702227856012802254       2025                        eng d  a1042-714700aOptimization and mechanistic insights of zinc ascorbate catalyst for ring-opening polymerization of caprolactone using RSM methodology and DFT calculations0 aOptimization and mechanistic insights of zinc ascorbate catalyst  cAPR  ae701820 v363 a<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>
10adensity function theory10aPolycaprolactone10aResponse surface methodology10aring-opening polymerization10azinc ascorbate1 aNaik, Sonali, S.1 aVedpathak, Shantanu1 aNair, Kiran, Sukumaran  uhttp://library.ncl.res.in/content/optimization-and-mechanistic-insights-zinc-ascorbate-catalyst-ring-opening-polymerization