Perspectives of ionic liquids applications for the synthesis of five- and six-membered O,N-heterocycles

A considerable attention has been paid on the use of ionic liquids in chemical research. Modern synthetic chemistry is benefited as ionic liquid methodology provided an environmentally benign approach. In comparison to traditional processes the use of ILs resulted in improved, complimentary or alternative selectivities in organic synthesis. This review focuses on the advances in the development of innovative applications of ionic liquids for the synthesis of five- and six-membered O,N-heterocycles.     

Ultrasound-assisted green synthesis of five-membered O- and S-heterocycles

This review gives an overview of utilization of ultrasound for the synthesis of various heterocyclic compounds. Ultrasonic irradiation has been considered as an efficient methodology in many organic syntheses. With ultrasonic assistance short reaction times, good selectivity and high yields are reported. The use of ultrasound irradiation in organic reactions has been increasing rapidly in recent years.     

Stable Borepinium and Borafluorenium Heterocycles: A Reversible Thermochromic “Switch” Based on Boron–Oxygen Interactions

The first examples of N-heterocyclic carbene (NHC) and cyclic(alkyl)(amino) carbene (CAAC) stabilized borepinium and borafluorenium heterocycles are reported herein. The optical properties of the heterocyclic borenium cations were tuned by varying the Lewis base and by changing the number of atoms in the ring. More importantly, functionalizing the cationic boron ring system in the NHC-borafluorenium cation affords a temperature-sensitive molecule with reversible colorimetric “turn off/turn on” properties in solution. Notably, this is the first report of thermochromism in these cationic species. This property, which is mediated by an intermolecular boron–oxygen bond equilibrium, was examined in detail by X-ray crystallography, variable temperature-UV/Vis absorption spectroscopy (VT-UV/Vis), and density functional theory (DFT).     

Fission analysis of Z = 114 superheavy isotopes formed via heavy-ion induced reactions

Journal of Radioanalytical and Nuclear Chemistry - The quasi-fission and fission mass distributions for 48Ti + 238U → 286Fl* and...     

Cyanoacetaldehyde as a building block for prebiotic formation of pyrimidines

The present study uses density functional theory to investigate the possible free radical pathways for cytosine and uracil formation from cyanoacetaldehyde in the presence of urea and ammonia. Our proposed mechanisms are characterized by a smaller number of precursors and relatively lower barriers compared to previously reported reactions with other prebiotic precursors. Thus, the proposed mechanisms are more plausible in environments like prebiotic earth and present-day Titan. Overall, this study suggests a kinetically accessible route to pyrimidine formation and will hopefully contribute toward understanding the relevance of these precursors in prebiotic reactions.     

Application of silver-promoted reactions in the synthesis of five-membered O-heterocycles

The investigation of facial protocols for chemical synthesis is a growing area of interest due to increasing environmental issues. The use of catalysts in organic reactions has gained extensive interest. Metal and nonmetal catalysts provided a new improved alternative to traditional methods in modern synthetic chemistry. The aim of the present review is to focus on the applications of silver-promoted reactions for the synthesis of oxygen containing five-membered heterocycles which have significance in organic synthesis, pharmaceuticals, agrochemicals, and among others.     

Theoretical molecular predictions and antimicrobial activities of newly synthesized molecular hybrids of norfloxacin and ciprofloxacin

Antibiotics such as norfloxacin and ciprofloxacin are used to treat numerous bacterial infections. The present research work involves the molecular prediction, synthesis, characterization and in vitro antimicrobial activities of molecular hybrids of norfloxacin and ciprofloxacin. First set of compounds involve the substitutions of various amines at third position of ciprofloxacin and norfloxacin. On the other hand, second set of molecular hybrids include the substitution of different amines at seventh position along with linker (─COCH₂─). These synthesized compounds were identified by TLC technique and well characterized by various spectroscopic techniques such as IR, NMR, and ESI-MS. Molecular prediction of these newly synthesized compounds have been carried out using the SwissADME, ADMETLab software. Their cytotoxicity parameters have also been studied using Osiris software. It was observed that almost all these molecular hybrids suitable for their drug likeness properties. Further, these newly synthesized compounds were subjected to study their antimicrobial activities in vitro. The third substituted as well as most of seventh substituted molecular hybrids have shown 10-folds increase in their antibacterial activity as compared to the standard drug ciprofloxacin. Some of these compounds have also shown their potency when subjected to study their cytotoxicity test against Escherichia coli AB 1157, proficient to prepare damage in DNA.     

Synthesis and Evaluation of Pyrazole Derivatives as Potent Antinemic Agents

Russian Journal of Organic Chemistry - Pyrazole derivatives were synthesized by bromination of pyrazole, followed by N-alkylation of 4-bromopyrazole. The synthesized derivatives were characterized...     

Chiral Bent-Shaped Molecules Exhibiting Unusually Wide Range of Blue Liquid-Crystalline Phases and Multistimuli-Responsive Behavior

Recently, an unprecedented observation of polar order, thermochromic behavior, and exotic mesophases in new chiral, bent-shaped systems with a −CH₃ moiety placed at the transverse position of the central core was reported. Herein, a homologous series of compounds with even-numbered carbon chains from n=4 to 18 were synthesized, in which −Cl was substituted for −CH₃ at the kink position and a drastic modification in the phase structure of the bent-shaped molecule was observed. An unusual stabilization of the cubic blue phase (BP) over a wide range of 16.4 °C has been witnessed. Two homologues in this series ( 1 -12 and 1 -14) exhibit an interesting phase sequence consisting of BPI/II, chiral nematic, twist grain boundary, smectic A, and smectic X (SmX) phases. The higher homologues ( 1 -16 and 1 -18) stabilize the SmX phase enantiotropically over the entire temperature range. Crystal structure analysis confirmed the bent molecular architecture, with a bent angle of 148°, and revealed the presence of two different molecular conformations in an asymmetric unit of compound 1 -4. A DFT study corroborated that the −Cl moiety at the central core of the molecule led to an increase in the dipole moment along the transverse direction, which, in turn, facilitated the unusual stabilization of frustrated structures. Crystal polymorphism has been evidenced in three homologues ( 1 -10, 1 -12, and 1 -14) of the series. On the application of mechanical pressure through grinding, compound 1 -10 transformed from a bright yellow crystalline solid to a dark orange–green amorphous solid, which reversed upon dropwise addition of dichloromethane, indicating reversible mechanochromism in this class of compounds. In addition, excellent thermochromic behavior has been observed for compound 1 -10 with a controlled temperature–color combination.