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An effective approach to separate chiral (2S,4S)-1-(tert-butoxy carbonyl)-4-(methoxymethyl) pyrrolidine-2-carboxylic acid ((2S,4S)-TBMP)) from mixed (2S,4S)-TBMP and (2S,4R)-1-(tert-butoxy carbonyl)-4-(methoxymethyl) pyrrolidine-2-carboxylic acid ((2S,4R)-TBMP), an important intermediate for the anti-HCV drug Velpatasvir, was developed for the first time, eliminating the need for salinization and dissociation processes and several organic solvents with water. Conceivable binding modes were set up by Gaussian calculation, and the separation process was designed and studied based on the calculation. The results showed that only the monohydrate of (2S,4S)-TBMP could be crystallized since three hydrogen bonds were formed between (2S,4S)-TBMP and water, which resulted in more stability and isomer separation. Compared to the original approach, our new approach exhibits a remarkable 17.4% increase in yield, a 43.3% rise in atom economy (AE), a 43.3% improvement in reaction mass efficiency (RME), and a substantial 32.0 g g−1 reduction in process mass intensity (PMI). An industrial-scale implementation was set up successfully according to the new approach, achieving a batch capacity of 100 kg. [ABSTRACT FROM AUTHOR]

With the development of pure organic room-temperature phosphorescence (ORTP), study in excitation-dependent fluorescence-phosphorescence (ExDFPh) dual emission materials is burgeoning. Herein, using formylphenylboronic acid (FPBA) as a prototype, the effect of substitution position on the ExDFPh properties was investigated. Among the three isomers, 4-FPBA exhibits outstanding ExDFPh behavior. Its luminescence color could turn from yellow to white to blue through decreasing the excitation energy. Importantly, dual phosphorescence-emitting species were observed and verified, which updates the understanding of the RTP mechanism. The difference in the ExDFPh behavior is possibly attributed to the RTP performance which is drastically affected by substitution position. Crystal analyses reveal that the intermolecular hydrogen-bond interaction changes from two to one to zero-dimension with varying substitution patterns from para- to meta- to ortho-position, which would affect the RTP emission. This is further proved by the comparison with the corresponding boronic ester, which contains no typical hydrogen bonds in the crystal structure. Theoretical calculation indicates that the intermolecular interaction would also play an important role in the intersystem crossing of the higher-lying singlet excited state. Based on the multi-color emission, potential application in anticounterfeiting is exhibited. [ABSTRACT FROM AUTHOR]

This article describes the synthesis of four new co-crystals obtained via cross-crystallisation of 2- and 4-mercaptopyridines with thiourea and trithiocyanuric acid and examines their crystal structures. The resulting structures are the first four reported co-crystals of mercaptopyridines. In one case, the synthesis resulted in the production of a ternary co-crystal of unexpected composition instead of the desired product and the correct co-crystal needed to be obtained under dark room conditions; interestingly, when separated from solution, all four co-crystal samples were fully light resistant. The crystal state of the four co-crystals is stabilized by several N–H⋯S type hydrogen bonds. Additionally, in the case of thiourea co-crystals, additional short contacts of S⋯S type are also observed. This relatively complicated network of intermolecular interactions is fully characterized herein. [ABSTRACT FROM AUTHOR]

Monoalkylation of aniline can be readily achieved using trichloroacetimidate as an alkylating agent and a Brønsted acid, such as (±)-camphorsulfonic acid, as a catalyst. In this study, systematic theoretical calculations were performed to understand the reaction mechanism for the monoalkylation of 2,5-dichloroaniline with trichloroacetimidate catalyzed by (±)-camphorsulfonic acid; moreover, the judgement about whether the reaction takes place via an SN1 or SN2 mechanism was elaborated. The two possible proton-transfer reaction mechanisms proposed herein based on the experimental results were investigated; moreover, another two possible reaction mechanisms involving the activation of both 2,5-dichloroaniline and trichloroacetimidate by (±)-camphorsulfonic acid via dual hydrogen-bonding activation modes were evaluated. The calculated results suggest that the reaction between 2,5-dichloroaniline and trichloroacetimidate catalyzed by (±)-camphorsulfonic acid preferentially occurs through the SN1 mechanism based on the dual hydrogen-bonding activation modes. [ABSTRACT FROM AUTHOR]

Co-crystals of 9,9′-dianthracene-10,10′-dicarboxylic acid (1) with the linear bidentate bases 9,9′-biacridine (bac), phenazine (phez), 4,4′-dipyridine (dpy), and DABCO (dabco) were synthesized. In the crystal structures of the co-crystals of 1 and bac, phez, and dpy, one-dimensional (1D) structures were formed through the hydrogen bonding between the acid and the base. For each combination of the acid and the bases, several kinds of polymorphic co-crystals with a similar structure were obtained. Among them, a combination of 1 and dabco gave three kinds of co-crystals which had a layered structure. In one of the co-crystals, a phenomenon where layers of the crystals could be exfoliated by dropping water was observed. The two-dimensional (2D) fingerprinting plot of the co-crystals showed that the major interaction to form the 1D structure was O–H⋯N hydrogen bonding and that to form the layered structure was the CH–π interaction, and the influence of the latter interaction on the robustness of the crystal was stronger than the former in the co-crystals. [ABSTRACT FROM AUTHOR]

1,2-Propanediaminetetraacetic acid (H4pdta = C11H18O8N2) is degraded selectively to 1-methyl-1,2-propanediaminetriacetic acid (H3pd3a = C9H16O6N2) with a yield of 75% at room temperature, while N-(2- hydroxyethyl) ethylenediaminetriacetic acid (H4eed3a = C10H18O7N2) is converted with difficulty to ethylenediaminetriacetic acid (H3ed3a = C8H14O6N2) on peroxotitanates(IV), showing the influence of the uncoordinated leaving group. Various species in the reaction sequence are isolated and fully characterized, including (NH4)[Ti(O2)(Hpdta)]·H2O (1), (NH4)3[Ti(O2)(pdta)H(pdta)(O2)Ti]·7H2O (2), (NH4)[Ti(O2)(pd3a)]·H2O (3) and (NH4)[Ti(O2)(Heed3a)]·H2O (5). Peroxo dimer 2 forms a strong intramolecular hydrogen bond [2.451(3) Å] as an intermediate in the peroxo Ti-pdta system, which results in the absence of a fully deprotonated species of peroxo pdta titanate. A catalytic reaction of the peroxo titanate (NH4)3[Ti(O2)(pdta)H(pdta)(O2)Ti]·7H2O (2) for the conversion of pyridine to pyridine N-oxide shows 94% conversion at 80 °C. [ABSTRACT FROM AUTHOR]

The dimeric receptor 1 from 1,2-phenylenediacetic acid and calcium ions recognized fluoride ions almost exclusively in 100% water. This recognition could be explained by the electrostatic interaction between Ca2+ and fluoride, complementarity of the receptor binding cavity size to the size of the fluoride ion, hydrogen bonding from benzylic C–H and the hydrophobic effect. DFT calculation results were in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]