One-pot multicomponent synthesis of tetrahydropyridines promoted by luminescent ZnO nanoparticles supported by the aggregates of 6,6-dicyanopentafulvene

Diastereo- and Enantioselective Synthesis of Highly Functionalized Tetrahydropyridines by Recyclable Novel Bifunctional C2-Symmetric Ionic Liquid–Supported (S)-Proline Organocatalyst

An efficient, novel bifunctional C2-symmetric ionic liquid–supported (S)-proline organocatalyst 7 was developed for a one-pot, five-component reaction involving β-keto esters 8, aryl aldehydes 9, and aryl amines 10, affording highly functionalized tetrahydropyridines 11a–o by simultaneous generation of fives bonds and two stereogenic centers with extraordinary diastereo- and enantioselectivities (up to >99:1 dr, 95:5 er) in isopropanol with high yields (up to 92%). This protocol provides quick access to diverse enantio-enriched, highly functionalized diastereo- and enantioselective tetrahydropyridines in a green medium without any column chromatographic purification. The catalyst was recycled five times without significant loss of its catalytic activity.

Versatile activity and morphological effects of zinc oxide submicron particles as anticancer agents

Background: Submicron particles (SMPs), as novel bionanomaterials, offer complementary benefits to their conventional nano-counterparts. Aim: To explore zinc oxide (ZnO) SMPs' bioimaging and anticancer potentials. Materials & methods: ZnO SMPs were synthesized into two shapes. Fluorescent spectrum and microscopy were studied for the bioimaging property. Wound healing and Live/Dead assays of glioblastoma cells were characterized for anticancer activities. Results: ZnO SMPs exhibited a high quantum yield (49%) with stable orange fluorescence emission. Both morphologies (most significant in the rod shape) showed tumor-selective properties in cytotoxicity, inhibition to cell migration and attenuating the cancer-upregulated genes. The tumor selectivity was attributed to particle degradation and surface properties on pH dependency. Conclusion: The authors propose that ZnO SMPs could be a promising anticancer drug with tunable, morphology-dependent properties for bioimaging and controlled release.

'Light-Up' AIE-Active Materials: Self-Assembly, Molecular Recognition and Catalytic Applications

Aggregation induced emission enhancement (AIEE) is one of the most widely explored phenomena to develop 'light up' (fluorescent) materials having potential applications in the field of supramolecular chemistry, analytical chemistry and material chemistry. By applying the principles of host-guest chemistry, we have developed a variety of aggregation induced emission (AIE/AEE) active materials having specific affinity for metal ions, electron deficient/electron rich analytes. The interactions between AIE active assemblies and metal ions are further tuned to prepare nanohybrids having potential applications as catalytic/photocatalytic systems in various organic transformations under eco-friendly conditions. This account summarizes various design strategies developed in our labortary for the preparation of AIE/AEE active building blocks having sensing and catalytic applications.

Cu(I)-Induced Activation of Furan for Inverse Electron Demand ADAR with Alkenes toward Regioselective Synthesis of Tetrahydropyridine

The aza-Diels-Alder reaction of various alkenes and in situ formed 1-aza-1,3-dienes from the reaction of furan/pyrrole/thiophene and PhINTs for the regioselective synthesis of tetrahydropyridine (THP) derivatives was realized. The reaction was catalyzed by Tp^Me2Cu as a catalyst under very mild reaction conditions. Structurally different alkenes, along with an alkyne, have been utilized as dienophiles to afford a wide range of different THP derivatives up to 70% yield. The potential application of the envisaged method was also investigated by a gram-scale synthesis.

Nanocrystalline ZnO: A Competent and Reusable Catalyst for the Preparation of Pharmacology Relevant Heterocycles in the Aqueous Medium

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Nanoparticle catalyzed synthesis is a green and convenient method to achieve most of the chemical transformations in water or other green solvents. Nanoparticle ensures an easy isolation process of catalyst as well as products from the reaction mixture avoiding the hectic work up procedure. Zinc oxide is a biocompatible, environmentally benign and economically viable nanocatalyst with effectivity comparable to the other metal nanocatalyst employed in several reaction strategies. This review mainly focuses on the recent applications of zinc oxide in the synthesis of biologically important heterocyclic molecules under sustainable reaction conditions.

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Application of zinc oxide in organic synthesis: Considering the achievable advantages of this nanocatalyst, presently several research groups are paying attention in anchoring zincoxide or its modified structure in several types of organic conversions e.g. multicomponent reactions, ligand-free coupling reactions, cycloaddition reaction, etc. The advantages and limitations of this nanocatalyst are also demonstrated. The present study aims to highlight the recent multifaceted applications of ZnO towards the synthesis of diverse heterocyclic motifs. Being a promising biocompatible nanoparticle, this catalyst has an important contribution in the fields of synthetic chemistry and medicinal chemistry.

Microwave-Assisted N-Allylation/Homoallylation-RCM Approach: Access to Pyrrole-, Pyridine-, or Azepine-Appended (Het)aryl Aminoamides

A facile and diversity-oriented approach has been developed for the synthesis of pyrrole-, pyridine-, or azepine-appended (het)aryl aminoamides via the N-allylation/homoallylation-ring-closing metathesis (RCM) strategy. Microwave condition was efficiently utilized for N-allylation of (het)aryl aminoamides to synthesize di-, tri-, and tetra-allyl/homoallylated RCM substrates in good yields. All of the RCM substrates were successfully converted to respective pyrroles 6a-h, 13a,b, 15a,b, pyridines 11a-d, 13c, and azepines 7a,b via RCM. All of the five-, six-, and seven-membered N-heterocycles were synthesized in shorter reaction times with excellent yields without isomerization products. A one-pot reaction to synthesize compounds 6a and 6b without isolating corresponding RCM substrates was achieved successfully. The synthetic utility of the compound 6b has been demonstrated by synthesizing biaryl derivatives 17a,b under the microwave Suzuki coupling reaction condition.

Metal nanoparticles embedded in AIEE active supramolecular assemblies: robust, green and reusable nanocatalysts

In modern organic synthesis, the utilization of metal NPs for carrying out fundamental organic transformations is an area of great interest. This frontier article describes the exploitation of supramolecular assemblies of AIEE-active materials as nanoreactors, stabilizers and shape directing agents for the preparation of various types of metal NPs without using any additives, reducing agents, stabilizing agents, etc. This article further summarizes the utilization of the as-prepared supramolecular ensembles as reusable nanocatalysts for carrying out various organic transformations under mild conditions.

Visible-light-mediated dehydrogenative cross-coupling between terminal alkynes and aldehydes by employing a supramolecular polymeric ensemble of PBI derivative

A supramolecular polymer of PBI derivative and ZnO NPs exhibits remarkable efficiency in direct dehydrogenative cross-coupling reaction for the synthesis of ynones under photocatalytic conditions.

Diastereoselective Synthesis of Symmetrical and Unsymmetrical Tetrahydropyridines Catalyzed by Bi(III) Immobilized on Triazine Dendrimer Stabilized Magnetic Nanoparticles

Unsymmetrical 1,2,5,6-tetrahydropyridine-3-carboxylates were obtained for the first time from a five-component Fe₃O₄@TDSN-Bi(III)-catalyzed reaction of aryl aldehydes, aryl amines, and ethyl acetoacetate. This magnetically separable catalyst enabled the selective incorporation of two different aryl amines or two different aryl aldehydes into the product, and provided excellent yields, short reaction times, mild reaction conditions, satisfactory catalyst recyclability, and low catalyst loading.

Green approach for synthesis of bioactive Hantzsch 1,4-dihydropyridine derivatives based on thiophene moiety via multicomponent reaction

A novel green and efficient one-pot multicomponent reaction of dihydropyridine derivatives was reported as having good to excellent yield. In the presence of the catalyst ceric ammonium nitrate (CAN), different 1,3-diones and same starting materials as 5-bromothiophene-2-carboxaldehyde and ammonium acetate were used at room temperature under solvent-free condition for the Hantzsch pyridine synthesis within a short period of time. All compounds were evaluated for their in vitro antibacterial and antifungal activity and, interestingly, we found that 5(b-f) show excellent activity compared with Ampicillin, whereas only the 5e compound shows excellent antifungal activity against Candida albicans compared with griseofulvin. The cytotoxicity of all compounds has been assessed against breast tumour cell lines (BT-549), but no activity was found. The X-ray structure of one such compound, 5a, viewed as a colourless block crystal, corresponded accurately to a primitive monoclinic cell.

Hexaphenylbenzene-based fluorescent aggregates for detection of zinc and pyrophosphate ions in aqueous media: tunable self-assembly behaviour and construction of a logic device

The aggregates of HPB derivative 7 exhibited “on–on” response towards Zn²⁺ ions and this in situ prepared 7-Zn2+ ensemble was utilized as a “not quenched” probe for detection of PPi ions in aqueous media.

C(sp3)–H dehydrogenation and C(sp2)–H alkoxy carbonylation of inactivated cyclic amines towards functionalized N-heterocycles

A novel and efficient synthesis of tetrahydropyridine-, dihydropyrrole-, and tetrahydroazepine-3-carboxylates via cascade reactions of cyclic amines with CO and alcohols is presented. To our knowledge, this should be the first example in which functionalized N-heterocycles were prepared through Pd-catalyzed C(sp³)–H dehydrogenation and C(sp²)–H carbonylation of cyclic amines.

Cu(ii)-grafted SBA-15 functionalized S-methylisothiourea aminated epibromohydrin (SBA-15/E-SMTU-CuII): a novel and efficient heterogeneous mesoporous catalyst

The catalytic activity of novel synthesized SBA-15/E-SMTU-Cu^II nanocatalyst was investigated for the green, one-pot, pseudo five-component synthesis of tetrahydropyridine derivatives.

Fluorescent aggregates of AIEE active triphenylene derivatives for the sensitive detection of picric acid

Fluorescent aggregates of triphenylene derivatives 3 and 5 having aggregation induced emission enhancement (AIEE) characteristics have been developed which selectively detect picric acid.

Aggregates of the pentacenequinone derivative as reactors for the preparation of Ag@Cu2O core–shell NPs: an active photocatalyst for Suzuki and Suzuki type coupling reactions

Aggregates of the pentacenequinone derivative stabilized Ag@Cu₂O core–shell nanoparticles (NPs) enabled efficient visible light harvesting to catalyse the palladium free Suzuki–Miyaura and Suzuki type cross coupling reactions at room temperature.