Search

The tunable properties of stimuli-responsive copolymers or hydrogels enable their application in different fields such as biomedical engineering, tissue engineering, or even drug release. Here we introduce a new PNIPAM-based triblock copolymer material comprising a controlled amount of a novel hydrophobic crosslinker 2,40 -diacryloyloxy benzophenone (DABP) and acrylic acid (AAc) to achieve lower critical solution temperature (LCST) between ambient and body temperatures. The dual stimuli-responsive p(NIPAM-coDABP-co-AAc) triblock copolymer material and hydrogel were synthesized, and their temperature and pHresponsive behaviors were systematically investigated. The hydrogel exhibited excellent temperature and pH-responsive properties with an LCST of around 30 1C. Moreover, the synthesized copolymer has been demonstrated to be nontoxic both in vitro and in vivo. When the hydrogel was preloaded with the model drug 5-fluorouracil (5-FU), the designed hydrogel released the drug in a temperature and pH-controlled fashion. It was observed that the prepared hydrogel has the ability to entrap 5-FU, and the loading is more than 85%. In the case of temperature-controlled release, we observed almost complete release of 5-FU at lower temperatures and sustained release behavior at higher temperatures. In addition, the hydrogel matrix was able to retard the release of 5-FU in an acidic environment and selectively release 5-FU in a basic environment. By realizing how the hydrogel properties influence the release of drugs from preloaded hydrogels, it is possible to design new materials with myriad applications in the drug delivery field. [ABSTRACT FROM AUTHOR]

This article provides an overview of the recent progress and prospects of using palladium nanoparticles (Pd NPs) as catalysts for the synthesis of functionalized heterocycles through C(sp2)-H arylation. Heterocycles are important in various fields, including pharmaceuticals and materials science. Traditional synthetic approaches have limitations, but transition-metal-catalyzed C-H activation offers a more efficient alternative. Heterogeneous catalytic approaches using Pd NPs show promise in terms of catalyst recoverability and reusability. The article discusses different methods and catalysts for the synthesis of functionalized heterocycles, highlighting their advantages and potential applications. [Extracted from the article]

The article discusses the use of benzoxazole and benzothiazole as directing groups for palladium- and ruthenium-catalyzed C-H arylation reactions. The authors explore different reaction conditions and catalysts to achieve selective arylation of these compounds. They also investigate the effects of substituents on the aryl unit and the benzoxazole/benzothiazole moiety. The document provides valuable information for researchers interested in the synthesis and functionalization of heterocyclic compounds. Additionally, the document includes experimental procedures and characterization data for specific compounds synthesized using the methods discussed. [Extracted from the article]

The application of bifunctional organocatalysts in organic chemistry has advanced remarkably owing to their high stability to moisture and air, relatively low toxicity, ease of handling, and recoverability. Among chiral bifunctional organocatalysts, squaramides have emerged as a privileged catalyst in recent years. This review article presents a comprehensive report on fine-tunable bifunctional chiral squaramide-catalyzed sulfa-Michael addition, which is based upon synchronous interplay of synergistic 'electrophilic–nucleophilic' dual activation strategies via multiple H-bonding interactions for the construction of both common and complex molecular entities bearing multiple stereocenters. Mechanistic discussions are kept brief, but significant understandings have been recorded. The contribution of squaramide catalyst to the construction of C–S bonds via sulfa-Michael addition has been applied in medicinal, natural, and industrial chemistry. Attention is focused on summarizing the progress made in chiral squaramide-catalyzed asymmetric sulfa-Michael addition and subsequent cascade/domino reaction sequences between 2011 and 2022. 1 Introduction 2 Quinine-Squaramide Organocatalysis 3 Iminophosphorane-Squaramide Organocatalysis 4 Chinchona-Squaramide Organocatalysis 5 trans -1,2-Diaminocyclohexane-Squaramide Organocatalysis 6 Conclusion [ABSTRACT FROM AUTHOR]

Functionalization of the bio‐relevant heterocycles 2‐arylbenzo[d]oxazole and 2‐arylbenzo[d]thiazole has been achieved through Ru(II)‐catalyzed alkenylation with unactivated olefins leading to selective formation of the mono‐alkenylated products. This approach has a broad substrate scope with respect to the coupling partners, affords high yields, and works for gram scale synthesis using a readily available Ru‐based catalyst. Mechanistic studies reveal a C−H activation pathway for the dehydrogenative coupling leading to the alkenylation. However, the results of the ESI‐MS‐guided deuterium kinetic isotope effect studies indicate that the C−H activation stage may not be the rate‐determining step of the reaction. The use of a radical scavenging agent such as TEMPO did not show any detrimental effect on the reaction outcome, eliminating the possibility of the involvement of a free‐radical pathway. [ABSTRACT FROM AUTHOR]

Abstract: Reported herein is the first example of a direct arylation of heteroarenes by a transient‐ligand‐directed strategy without the need to construct and deconstruct the directing group. A wide range of heteroarenes undergoes the coupling with diverse aryl iodides to assemble a large library of highly selective and functionalized 3‐arylthiophene‐2‐carbaldehydes. This route provides an opportunity to rapidly access new mechanofluorochromic materials. Moreover, a novel strategy for mechanochromic luminogens with chromism trends of red‐ and blue‐shifts has been disclosed for the first time by facile functional‐group modifications to a common structural core. [ABSTRACT FROM AUTHOR]

An ecofriendly approach for the synthesis of highly substituted tetrahydropyridines by an 'on-water' multicomponent reaction has been demonstrated. The use of water as the reaction medium is essential under the catalytic influence of a surfactant. The use of a variety of anionic, cationic, and non-ionic surfactants in water was examined and the reaction was successfully catalyzed by anionic surfactants sodium dioctyl sulfosuccinate (SDOSS) and sodium dodecyl sulfate (SDS), with the former being superior. The use of an organic solvent together with a catalytic amount of sodium dioctyl sulfosuccinate to form homogeneous conditions afforded inferior yields and highlighted the specific role of water through the creation of microreactors at the water surfactant interface. A mechanistic insight for the five-component reaction leading to the formation of tetrahydropyridines is provided invoking a tandem inter- and intramolecular Mannich reaction pathway. [ABSTRACT FROM AUTHOR]

A novel strategy for direct aryl hydroxylation via Pd-catalysed A novel strategy for direct aryl hydroxylation via Pd-catalysed Csp2-H activation through an unprecedented hydroxyl radical transfer from 1,4-dioxane, used as a solvent, is reported with bio relevant and sterically hindered heterocycles and various acyclic functionalities as versatile directing groups. activation through an unprecedented hydroxyl radical transfer from 1,4-dioxane, used as a solvent, is reported with bio relevant and sterically hindered heterocycles and various acyclic functionalities as versatile directing groups. [ABSTRACT FROM AUTHOR]

Thepalladium–nickel binary nanocluster is reported as anew catalyst system for Suzuki–Miyaura cross-coupling of ortho-heterocycle-tethered sterically hindered aryl bromides.The inferior results obtained with the reported Pd/Ni salts/complexesor individual Pd/Ni nanoparticles as catalyst reveal the cooperativecatalytic effect of the Pd and Ni nanoparticles in the Pd–Ninanocluster. The broad substrate scope with respect to variation ofthe 2-arylbenzoxazole moiety and boronic acids, which offers a meansfor diversity generation and catalyst recyclability, marks a distinctadvantage. [ABSTRACT FROM AUTHOR]

The tunable properties of stimuli-responsive copolymers or hydrogels enable their application in different fields such as biomedical engineering, tissue engineering, or even drug release. Here we introduce a new PNIPAM-based triblock copolymer material comprising a controlled amount of a novel hydrophobic crosslinker 2,4'-diacryloyloxy benzophenone (DABP) and acrylic acid (AAc) to achieve lower critical solution temperature (LCST) between ambient and body temperatures. The dual stimuli-responsive p(NIPAM- co -DABP- co -AAc) triblock copolymer material and hydrogel were synthesized, and their temperature and pH-responsive behaviors were systematically investigated. The hydrogel exhibited excellent temperature and pH-responsive properties with an LCST of around 30 °C. Moreover, the synthesized copolymer has been demonstrated to be nontoxic both in vitro and in vivo . When the hydrogel was preloaded with the model drug 5-fluorouracil (5-FU), the designed hydrogel released the drug in a temperature and pH-controlled fashion. It was observed that the prepared hydrogel has the ability to entrap 5-FU, and the loading is more than 85%. In the case of temperature-controlled release, we observed almost complete release of 5-FU at lower temperatures and sustained release behavior at higher temperatures. In addition, the hydrogel matrix was able to retard the release of 5-FU in an acidic environment and selectively release 5-FU in a basic environment. By realizing how the hydrogel properties influence the release of drugs from preloaded hydrogels, it is possible to design new materials with myriad applications in the drug delivery field.

Functionalization of the bio-relevant heterocycles 2-arylbenzo[d]oxazole and 2-arylbenzo[d]thiazole has been achieved through Ru(II)-catalyzed alkenylation with unactivated olefins leading to selective formation of the mono-alkenylated products. This approach has a broad substrate scope with respect to the coupling partners, affords high yields, and works for gram scale synthesis using a readily available Ru-based catalyst. Mechanistic studies reveal a C-H activation pathway for the dehydrogenative coupling leading to the alkenylation. However, the results of the ESI-MS-guided deuterium kinetic isotope effect studies indicate that the C-H activation stage may not be the rate-determining step of the reaction. The use of a radical scavenging agent such as TEMPO did not show any detrimental effect on the reaction outcome, eliminating the possibility of the involvement of a free-radical pathway., (© 2020 Wiley-VCH GmbH.)