Search

Abstract: The remarkable improvements in organic synthesis facilitated by zirconium dioxide-based nanoparticles are updated and summarized in this review. The ZrO2 acts as a versatile heterogeneous nanocatalyst and is used in various elementary organic reactions and many multicomponent reactions. The employment of these catalysts in organic synthesis leading to bio-active scaffolds provides the opportunity to carry out the reactions using facile synthetic protocol under mild environments that furnish the equivalent products in high yields and shorter reaction times. According to reports in the literature, ZrO2-based catalysts were removed from the reaction mixture and recycled many times.

An ICl-mediated highly chemo- and regioselective functional group interconversion from methyl homopropargyl ether to α-iodo-γ-chloro-ketone is reported. Density functional theory (DFT)-calculated reaction coordinate and potential energy surface support the high chemo-selectivity observed for the formation of α-iodo-γ-chloroketone over furan. The five-membered oxonium ring formation-ring opening mechanism is a potential template for the preparation of polyfunctionalized carbonyl compounds.

In modern organic synthesis, the execution of reactions in the absence of expensive transition metals has received significant attention from the view-point of green chemistry and sustainable development. As a consequence, the combination of MI-TBHP as an oxidation system (M = Na, K, NH4) has opened a new avenue with significant impact for the succinct synthesis of complex heterocycle molecules via the construction of various chemical bonds [C-X (X = C, N, S, O), N-X (X = N, P) and S-N]. This comprehensive review article delineates the progress of recent developments in this emerging area, with an in-depth discussion on the substrate scope, limitations and proper mechanistic underpinnings. We hope this review will highlight the great potential of this MI-TBHP as a powerful oxidation system and inspire researchers to conduct further endeavors in this domain.

Indole and its congeners are ubiquitous nitrogen-containing organic scaffolds present in a plethora of natural products, marketed drugs, and other organic functional molecules. Recent years have witnessed tremendous advances in the diversification of this motif and its biological applications via transition-metal-catalyzed auxiliary assisted site-selective inert C–H functionalization. In this burgeoning field, N-methoxy/ethoxy/pivaloxy amide functionality has emerged as a most potent auxiliary/DG (directing group) for a wide range of C–C and C–heteroatom bond formations, providing a new advance for forging structurally fabricated polycyclic indole frameworks. This review aims to highlight evolved transformations, like arylation, alkylation, alkenylation, allylation, amidation, difluorovinylation, deuteration, hydroarylation, etc., and the applications of N-alkoxycarbamoyl indole derivatives made within the period of 2014–August 2021. Additionally, explicit mechanistic underpinnings have also been provided in the appropriate places.

An expeditious metal free C-3 chalcogenation of 4H-pyrido[1,2-a]pyrimidin-4-one has been devised to synthesize diversely orchestrated 3-ArS/ArSe derivatives in high yields (up to 95%). This operationally simple reaction proceeds under mild reaction conditions, can be executed in gram scale, and also highlights broad functional group tolerance. Preliminary experimental investigation suggests a radical mechanistic pathway for these transformations.

Palladium catalyzed arylation of the inert β-C(sp2)–H bond of carboxylic acid derivatives is reported herein for the first time utilizing 8-aminoimidazo[1,2-a]pyridine (AIP) as an efficacious and new inbuilt 6,5-fused bicyclic removable directing group. This protocol is scalable, exhibits high levels of β-site selectivity and tolerates a broad spectrum of functional groups.

We demonstrate herein the first example of a palladium(II) catalyzed regioselective ortho-C(sp2)–H arylation in aqueous medium (a sustainable solvent) utilizing 8-AIP (8-aminoimidazo[1,2-a]pyridine) as a promising and removable bidentate directing group/auxilliary. This newly developed protocol features a broad substrate scope with excellent functional group tolerance and enables an expeditious route to a library of unsymmetrical amides in good to excellent yields with exclusive site-selectivity.

Over the past few decades, quinoxalin-2(1H)-one derivatives are serving as active components in diverse families of drugs such as antimicrobial, anticancer, antithrombotic agents and protein kinase...

Background: Green and sustainable method for the oxidation of aldehydes into acids is now in demand as carboxylic acids are important and versatile intermediates. In this context, visible LED light-promoted aerial oxidation can be efficient and greener protocol. Objective: Herein, we have demonstrated a visible LED light-promoted efficient and greener protocol for the aerial oxidation of aromatic aldehydes into corresponding acids in the absence of any additives, base, catalyst, and oxidant. Methods: The oxidation of aromatic aldehydes was irradiated by an LED light at room temperature under an open atmosphere, monitored by TLC. The rate of oxidation was also monitored using different LED lights by UV-Vis studies. The products were purified by column chromatography using silica gel, and the mixture of ethyl acetate/petroleum ether as an eluting solvent and the pure products were confirmed by their melting point determination and NMR spectroscopic analysis. Results: The aldehydes were successfully converted into corresponding acids with good isolated yields (60-90 %) by this protocol, where blue LED light (l ~ 490 nm) was found to be the best choice. Conclusion: The present protocol of aerial oxidation of aromatic aldehydes into corresponding acids under visible LED light has been carried out in the absence of catalyst, oxidant, base, and any other additives. The higher isolated yields, no byproduct formation, and neat reaction conditions are the major advantages of the protocol.

A unique

Quinazolinone and its congeners are ubiquitous structural motifs found in numerous natural products due to their wide applications as anticancer, antiviral, anti-inflammatory, antifolate and antitumor agents etc. Previously, the synthetic community devoted their efforts towards synthetic approaches but recent years have also witnessed an upsurge in the diversification of this scaffold and its applications. Thus, this review (from 2011 to the beginning of 2020) comprehensively focuses on transition metal catalyzed C-H bond functionalization namely arylation, amination, acetoxylation, amidation, alkylation, alkenylation, alkynylation, halogenation, thiolation, trifluoroethylation etc. of quinazolin-4(3H)-one. Additionally, we also briefly elucidate the plausible mechanistic pathways, scope and limitations.

Indiscriminate use of antibiotics in broiler could lead to residue accumulation in food chain. We conducted a study to detect colistin residues in broiler meat in different growth stages, collected from different upazilas of Mymensingh division. A total of 108 samples, were collected from Fulbaria, Mymensingh Sadar, and Trishal Upazila of Mymensingh district and Nakla Upazila of Sherpur district. From each farm, nine samples were collected at the three different growth stages: 14-20 days (Early:E), 21-27 (Middle:M) days and 28-35 (Late:L) days, respectively. Thin layer chromatography (TLC) was used for the qualitative detection colistin residues in broiler meat. A questionnaire survey was carried out with the farmers from whom the samples were collected. Most of the farmers’ had varying degree of knowledge about biosecurity, withdrawal period and residue of antibiotic, and academic qualification varies from primary to graduate level. Out of 108 samples, 50% (18 out of 36) samples were positive for TLC in early samples, whereas 66.67% (24 out of 36) samples for middle and 50% (18 out of 36) for late collected samples. Upazila-wise, the highest concentration was detected in Mymensingh sadar and Nakla (66.67%) and lowest in Fulbaria (33.33%). These result indicates that colistin are being misused in poultry industry especially in middle days of broiler life and withdrawal periods are not maintained when broiler are marketed. Being a Reserve group antibiotics, measures are needed to ensure human safety regarding colistin residue in poultry industry. Asian Australas. J. Food Saf. Secur. 2019, 3(1), 43-47

In modern organic synthesis, the execution of reactions in the absence of expensive transition metals has received significant attention from the view-point of green chemistry and sustainable development. As a consequence, the combination of MI-TBHP as an oxidation system (M = Na, K, NH4) has opened a new avenue with significant impact for the succinct synthesis of complex heterocycle molecules via the construction of various chemical bonds [C-X (X = C, N, S, O), N-X (X = N, P) and S-N]. This comprehensive review article delineates the progress of recent developments in this emerging area, with an in-depth discussion on the substrate scope, limitations and proper mechanistic underpinnings. We hope this review will highlight the great potential of this MI-TBHP as a powerful oxidation system and inspire researchers to conduct further endeavors in this domain.

We demonstrate herein the first example of a palladium(ii) catalyzed regioselective ortho-C(sp2)-H arylation in aqueous medium (a sustainable solvent) utilizing 8-AIP (8-aminoimidazo[1,2-a]pyridine) as a promising and removable bidentate directing group/auxilliary. This newly developed protocol features a broad substrate scope with excellent functional group tolerance and enables an expeditious route to a library of unsymmetrical amides in good to excellent yields with exclusive site-selectivity.

Palladium catalyzed arylation of the inert β-C(sp2)-H bond of carboxylic acid derivatives is reported herein for the first time utilizing 8-aminoimidazo[1,2-a]pyridine (AIP) as an efficacious and new inbuilt 6,5-fused bicyclic removable directing group. This protocol is scalable, exhibits high levels of β-site selectivity and tolerates a broad spectrum of functional groups.

Owing to the fascinating applications of ionic liquids (ILs) based non-aqueous microemulsions (MEs) in the field of chemical reactions due to their high thermal stability compared to that of aqueous MEs and requirement of water-free environment, we designed a high-temperature stable cationic IL-in-oil microemulsions using 1-ethyl-3-propylbenzimidazolium bromide ([EPbim][Br]) as a polar phase for the first time. In order to determine the thermodynamic stability of such type of MEs, we measured the distribution of cosurfactant (herein, 1-octanol) between bulk n-decane phase and interface covered by quaternary ammonium head group of cetyltrimethylammonium bromide (CTAB) at elevated temperature. The spontaneous formulation of high-temperature IL-in-oil MEs with organized IL-oil interface was identified by the negative free energy and entropy change at studied temperature range (358–370 K). Interestingly, we observed temperature-independent exothermic behavior at a specific composition, which probably comes from the cation-π interaction between quaternary ammonium head group of CTAB and aromatic moiety of ILs. We performed phase behavior study to demonstrate a wide range of thermally stable of [EPbim][Br]/CTAB/decane MEs. Surprisingly, the droplet size was decreased with progressive addition of IL, which may be due to the difficulty of formation of strong and favourable H-bond between the polar head groups of CTAB and [EPbim][Br] at higher temperature. Furthermore, the aggregation number and molecular interfacial area at higher temperature were calculated, which have direct correlation with the droplet size. Finally, the nitration reaction with three different aromatic compounds was performed in this MEs media at the temperature-independent composition. The reaction was completed with the highest regioselectivity of para isomer product over the ortho one. Moreover, these results clearly highlight an efficient way towards the formulation of high temperature stable MEs with ILs at ambient pressure and open a wide field of potential applications.

An operationally simple sodium iodide-mediated C-S and C-Se bond formation protocol involving substituted 4-quinolone and thiols/diselenide to generate different ArS/ArSe-substituted 4-quinolone derivatives in excellent yields was developed. The versatility of this methodology has been successfully demonstrated by extension of the suitable reaction conditions to both substrates having different substituents. This regioselective C-H bond activation approach provides a direct access of structurally diverse 3-sulfenylated/selenylated 4-quinolone derivatives. Moreover, this new method proceeds without a transition-metal catalyst and prerequisite NH protection of 4-quinolone derivatives.

Carbonylative Sonogashira annulation sequence for one pot synthesis of 4-quinolone and 4H-chromen-4-one has been developed in presence of Pd-NHC catalyst. Substituted 2-iodoaniline and 2-iodophenol independently underwent in the carbonylative Sonogashira annulation reaction with a variety of acetylenes to result in 4-quinolone and flavone derivatives respectively in good to excellent yield. Moreover, this protocol does not require toxic CO gas, high catalyst loading and any expensive salt/additive. Herein we, for the first time, are using Mo(CO)6, as solid CO source for the one pot synthesis of flavone derivatives via carbonylative Sonogashira annulation reaction.

We unfold a rapid synthetic protocol for the preparation of imidazo[1,2-a]pyridine in cyclohexane. This methodology includes several advantages like shorter reaction time, catalyst free, broader substrate scope, and good yields of the desired products. Late stage functionalization of imidazo[1,2-a]pyridine has also been performed through C–H bond activation and C–C cross-coupling reactions.

We report the synthesis of biaryl ketones via an unprecedented copper/silver catalyzed acylative cross-coupling of thiol esters with either an arylboronic acid or a potassium aryltrifluoroborate. This new method proceeds without a requisite Pd-catalyst and Cu(I)TC mediator, and is efficient, versatile, operationally simple, and accommodating functionally diverse thiol esters, arylboronic acids, and potassium aryltrifluoroborates.

Regiocontrolled nitration of 4-quinolone, the highly privileged scaffold, has been developed at ambient conditions. The nitro group can selectively be introduced at diverse positions simply by tuning the reactivity of the moiety. Discrimination is being achieved through the selective functionalization of the free N-H group. The functional group has been screened theoretically with the help of Fukui function and local softness calculation. Theoretical predictions are synchronized well with the experimental findings. Finally, this nitration technique allows quick access to the structurally diverse 4-quinolones.

Recent advances in technology and manufacturing have made it possible to create small, powerful, energy-efficient, cost-effective sensor nodes for specialized telecommunication applicationsnodes "smart" enough to be capable of adaptation, self-awareness, and self-organization. Sensor Networks for Sustainable Development examines sensor network technologies that increase the quality of human life and encourage societal progress with minimal effect on the earths natural resources and environment. Organized as a collection of articles authored by leading experts in the field, this valuable reference captures the current state of the art and explores applications where sensor networks are used for sustainable development in: Agriculture Environment Energy Healthcare Transportation Disaster management Beneficial to designers and planners of emerging telecommunication networks, researchers in related industries, and students and academia seeking to learn about the impact of sensor networks on sustainable development, Sensor Networks for Sustainable Development provides scientific tutorials and technical information about smart sensor networks and their use in everything from remote patient monitoring to improving safety on the roadways and beyond.

An auto-tandem palladium catalysis from halogen-substituted isoxazoles and Michael acceptors is described. It involves two mechanistically distinct palladium-catalyzed reactions, a Heck reaction and a rearrangement, leading to 2-azafluorenones. It is the first example of palladium-catalyzed ring opening of isoxazoles and rearrangement of the β-imino ketone ring-opening product.

A simple, competent, green pathway has been developed for the Pd catalyzed ligand free homocoupling reaction of arylboronic acids in water under ambient conditions. An efficient reaction environment is generated using a combination of Pd(OAc)2 and ‘green additives’, which exhibited excellent activity and results in high yields of the desired coupled products within 15 minutes.

Regio-controlled nitration of 4-quinolone, the highly privileged scaffold, has been developed at ambient conditions. Nitro group can selectively be introduced at diverse position simply by tuning the reactivity of the moiety. Discrimination is being achieved through the selective functionalization of free N-H group. The functional group has screened theoretically with the help of Fukui function and local softness calculation. Theoretical predictions are synchronized well with the experimental findings. Finally, this nitration technique allows the quick access of the structurally diverse 4-quinolones.

Microemulsions (mEs), being thermodynamically stable, single phasic transparent mixtures of oil, water, surfactant ( either individually or in mixed state) and/or co-surfactant, are exemplary and multi dimensional reaction media in organic synthesis. They can act as an alternative of the phase transfer catalysis and influence the rate of the reaction due to the presence of charged carriers (amphiphiles) at the oil/water interface. The regioselectivity of many organic reactions can also be induced by employing mEs as templates. In particular, organic molecules with different degrees of polarity tend to accumulate at the oil/water interface of mEs. Subsequently, they orient themselves at the interface in such a way that the polar component extends into the water domain and the nonpolar component protrudes towards hydrocarbon domain. In view of this, a water-soluble reagent attacks the polar part of the amphiphile, and a reagent soluble in hydrocarbon reacts at the nonpolar part of the amphiphile. Because of this unique feature, use of mEs (or micro heterogeneous systems) as templates for studying organic reactions, have increased manifolds. In this short review, we mainly exemplify (i) mEs as reaction media, (ii) effect of microstructure of mEs on organic transformations and (iii) the most possible reaction location/site in mEs.