Letters in Organic Chemistry - Volume 20, Issue 10, 2023

The conformational features of vinyl isocyanate (1) and vinyl azide (2) have been analyzed using G4MP2, CCSD(T)/6-311+G**, B3LYP/6-311+G** and LC-ωPBE/6-311+G** theory levels. Published experimental data indicate that the stability of the cis-isomer of vinyl azide (2) is more than the trans-isomer. This is consistent with the findings attained using G4MP2 and LC-ωPBE/6- 311+G** levels, whereas B3LYP/6-311+G** and CCSD (T)/6-311+G** levels provide false energetic outcomes. Natural Bond Orbital (NBO) interpretation is used to interpret the reason for the stability of the cis stereoisomer of compound 2 and the structural features of compound 1. Dipole-dipole interactions, steric effects, and resonance energies on the structural behaviors of compounds 1 and 2 are also investigated using NBO analysis. The results showed that the stability of the cis conformer of compound 2 compared to its trans conformer could be explained using the steric effect (Pauli Exchange Type Repulsion or PETR). Dipole moments of the cis conformer of compound 2 are evaluated experimentally (from Rotational Spectroscopy) and theoretically. The experimental (from Rotational Spectroscopy) and theoretically evaluated dipole moments of trans-conformation of compound 2 are slightly greater than that in cis-conformation, which is in favor of the cis-conformation, while dipoledipole interactions are in favor of the cis-conformation of compound 1. Accordingly, the electrostatic interactions associated with dipole-dipole interactions do not explain the conformational behaviors of compound 1. The stabilization energies related to the delocalization of electrons are in favor of the cis-conformation of compound 1, whereas it has no considerable effect on compound 2’s conformational behavior.

Artificial enzyme mimics have lately sparked a lot of attention since they offer a lot of benefits over natural enzymes. Because of their proteic origin and tailorable structures, self-assembling peptides are ideal building blocks for the creation of artificial enzymes. Recently, a series of histidinebearing self-assembling peptides with β-sheet structures, which are selective for short-chain fatty acids, were described. In this work, the catalytic behaviors of these peptides were further investigated using 2,4-dinitrophenyl acetate (DNPA) as a model substrate. Furthermore, the peptide was capable of forming a solid hydrogel that was also catalytically active at higher concentrations.

Amphiphilic tri-arm star-shaped copolymers, poly(ethylene oxide)-b-poly(ε-caprolactone) PEO3-b-PCL3, with different poly (ε-caprolactone) (PCL) molecular weights were successfully synthesized by ring-opening polymerization (ROP). Firstly, the tri-arm star-shaped PEO3 was prepared by ROP of trimethylolpropane and ethylene oxide (EO). The ring-opening polymerization (ROP) of ε- caprolactone (CL) was initiated using the tri-arm star-shaped PEO3 with the hydroxyl group as macroinitiator and Sn(Oct)2 as a catalyst. Amphiphilic tri-arm star-shaped copolymers PEO3-b-PCL3 were obtained. By changing the ratio of monomer and macroinitiator, a series of PEO3-b-PCL3 were prepared with a well-defined structure, molecular weight control, and narrow molecular weight distribution. The expected intermediates and final products were confirmed by ¹H NMR and Gel Permeation Chromatography (GPC) analyses. In addition, the sizes and morphologies of the obtained micelles with different PCL segment lengths were investigated with dynamic light scattering (DLS) and transmission electron microscopy (TEM), respectively. It was found that the self-assembly morphologies were spherical micelle in aqueous solution.

A simple and efficient synthesis of pyrrolo[1,2-a]pyrazine using Schiff base formation, intramolecular cyclization (or N-alkylation), and Pictet–Spengler type reaction (hetero-aromatisation) has been developed. In this chemistry, metal-free, cost and time-effective processes have been highlighted to afford the complex nitrogenous scaffold using simple starting materials.

The development of efficient and eco-friendly synthetic processes or techniques for the synthesis of heterocyclic compounds is increasing enormously. Here, an environmentally friendly ionic liquid is used as an efficient catalyst for the synthesis of biologically important dihydropyrano [3,2- c] chromenes. This is because ionic liquids play an important role in green chemistry due to their distinctive properties, easy handling, non-toxicity, increased reaction selectivity, and low solubility. This review focuses on dihydropyrano [3,2-c] chromenes synthesis due to their great importance as natural products, pharmaceuticals, and bioactive molecules. The review summarizes the application of ionic liquids as an effective catalyst for the multicomponent synthesis of dihydropyrano [3,2-c] chromene derivatives by using aromatic aldehydes, 4-hydroxycoumarin, and malononitrile in a green chemical manner.

Anilinopyrimidines have a wide range of biological activities, including antibacterial, antifungal, and anticancer effects. They have a wide range of uses and opportunities due to their varied experimental preparation and study activities. This creates a lot of interest, experiments and analytical analyses are still being conducted to understand their medicinal chemistry better. According to their effects, which can include antifungal and antibacterial, anticancer or antitumor, and other properties, anilinopyrimidines are categorized in this review. In conclusion, it is critical to base the design of new anilinopyrimidine derivatives and the creation of novel synthesis methodologies on the most recent information discovered through recent research. This review intends to shed light on advancements in the synthetic and biological activity of analogs of anilinopyrimidines.

Various catalytic and non-catalytic organic transformations are carried out in glycerol media with superior efficiency over commonly employed organic solvents. The success of glycerol as a green media is due to its exceptional H-bonding properties, which result in enhanced reactivity in many organic transformations. In addition, its highly polar nature and non-toxic properties, recyclability, large availability as an organic waste from the biodiesel industry, high boiling point, low vapor pressure and low price further extend the scope of this solvent as green media. In this review, we present the potential use of glycerol as a green solvent in many organic transformations in two sections: cyclization reactions and miscellaneous reactions.

Conductive clay–polymer nanocomposites were preparedvia the in situ polymerization of aminoacetophenone and/or aniline monomers (at initial “aminoacetophenone:aniline”) in the presence of polyhydroxy iron cation–modified montmorillonite (MMT-PIC). Fourier transform infrared spectroscopy analysis demonstrated the characteristic bands of the MMT-PIC polymers/copolymers. The morphological properties analyzed and imaged through X-ray diffraction and scanning electron microscopy, respectively, displayed an increasing interlayer distance with the mass loading of PIC and poly(aminoacetophenone-co-aniline) (poly(AAP-co-ANI)), affording intercalated nanocomposites. Energy-dispersive X-ray spectroscopy measurements revealed that the clay experienced a cation exchange of sodium by the PIC, and poly(AAP-co-ANI) was present in large amounts on the nanocomposite surface. The electrical conductivity of the obtained nanocomposites was 5.760 × 10⁻⁵ Scm⁻¹. Moreover, the electrochemical behavior of the polymers extracted from the nanocomposites was studied via cyclic voltammetry; the redox processes indicated that the polymerization into activated carbon produced electroactive polymers.

In this present investigation, efficient and general protocols for the synthesis of a series of imidazoles 4(a-p) derivatives have been developed by cyclocondensation of aromatic aldehydes, benzil and ammonium acetate in the existence of efficient [EMIm][BH3CN] ionic liquid catalyst under microwave condition in good to excellent yields (91-97%). The structures of the synthesized compounds have been confirmed by IR and NMR spectra. The significant features of this protocol are an uncomplicated workup process, rate enhancement with high yields, and efficient catalysts. It was concluded that [EMIm][BH3CN] is the finest catalyst under MW heating conditions.

Specific recognition at trace quantity levels of metal ions without using the costly analytical instrument and a tedious sample preparation method is an extensive concern for environmental monitoring and mitigation. Mercury(II) (Hg²⁺) has acute toxicity. The development of ion-selective fluorescence sensors for the selective detection of Hg²⁺ is an essential task to accomplish. The aim of this study is to detect Hg²⁺ in an aqueous medium. A fluorescence sensor (DP) based on Schiff base was designed and utilized to detect Hg²⁺. Scanning electron microscope (SEM), Fourier transformed Infrared (FT-IR), X-ray powder diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to learn the sensing mechanism between sensor DP and Hg²⁺ cations. When Hg²⁺ ions were added to the sensor DP, it showed a dramatic fluorescent “turn-on” response for Hg²⁺ in dimethylformamide (DMF) solution. And the detection limit (LOD) of DP for Hg²⁺ in aqueous media (1.0 mol L^-1) was 2.23 × 10-8 mol L^-1. In summary, an aminoantipyrine-containing Schiff base fluorescent chemosensor for extraordinary recognition of Mercury(II) was designed and synthesized via a simple one-step pathway and led to intermolecular self-assembly through π-π stacking interactions. And the sensor DP could fluorescently “turn on” when the Hg²⁺ cation was added. The limitation of Hg²⁺ was 2.23×10-8 M, which indicated that the sensor DP could be useful as a highly selective and sensitive sensor for detecting Hg²⁺ ions in an aqueous medium by the strong interaction with DP. Notably, the sensor DP was used as a fluorescent display material with satisfactory results.

During the process optimization of Lisdexamfetamine dimesylate, two process impurities were observed. Methods: These impurities remained a concern for commercialization and were isolated, on characterization, were found to be H-Lys-ε-Lys-d-amphetamine and other being its regio- isomer H-Lys-α-Lysd- amphetamine. The main target of this study was to synthesize reference compounds for HPLC analysis of these impurities produced in Lisdexamfetamine. Result: To the best of our knowledge, these impurities are not commercially available and no synthetic methods have been reported. Both of these potential impurities were synthesized, and their structures were established by various spectral techniques. Conclusion: Furthermore, herein we also report the synthesis of two process impurities Boc- Lys(Boc)-ε-Lys(α-Boc)-O-Nitrophenol and Boc-Lys(Boc)-α-Lys(ε-Boc)-O-Nitrophenol and their fate for the formation of impurities H-Lys-ε-Lys-d-amphetamine and H-Lys-α-Lys-d-amphetamine.

The first synthesis of 2-bromogentisyl alcohol, a halogenated compound cytotoxicity to breast cancer cell line, was achieved in four steps. Key steps include (i) formylation of aromatic compound, (ii) bromination, (iii) demethylation and (iv) reduction. Compound 3 was prepared from 4- methoxyphenol (2) in 92% yield in the presence of MgCl2 and Et3N, then intermediate 4 was obtained by bromination of 3 in 78% yield. Subsequently, the direct demethylation of 4 with BBr3 afforded the intermediate 5 in 72% yield. Finally, title compound 1 was prepared by the reduction of 5 using NaBH4 in 87% yield. The overall yield is 45% from 4-methoxyphenol. This method is simple and the reaction conditions are mild.