Microwave-assisted organic synthesis and transformations using benign reaction media

Recyclable imidazolium ion-tagged nickel catalyst for microwave-assisted C–S cross-coupling in water using sulfonyl hydrazide as the sulfur source

Recyclable nickel(ii) catalyst promoted sulfenylation of aryl halides with sulfonyl hydrazides in water using microwave irradiation under mild conditions is reported.

An Efficient, Eco-friendly and Sustainable One-Pot Synthesis of 3,4-Dihydropyrimidin-2(1H)-ones Directly from Alcohols Catalyzed by Heteropolyanion-Based Ionic Liquids

Efficient, eco-friendly and sustainable access to 3,4-dihydropyrimidin-2(1H)-ones directly from alcohols under microwave and solvent-free conditions has been reported. The practical protocol involves heteropolyanion-based catalyzed oxidation of alcohols to aldehydes with NaNO₃ as the oxidant followed by cyclocondensation with dicarbonyl compounds and urea or thiourea in a two-step, one-pot manner. Compatibility with different functional groups, good to excellent yields and reusable catalysts are the main highlights. The utilization of alcohols instead of aldehydes is a valid and green alternative to the classical Biginelli reaction.

An efficient synthesis of naphtho[2,1-b]furan-2(1H)-ones catalysed by Nafion-H supported on silica-coated super paramagnetic iron oxide nanoparticles

A one-pot procedure is descibed for the synthesis of naphtho[2,1- b]furan-2(1 H)-ones via a multicomponent reaction of aryl aldehydes, hippuric acid, acetic anhydride and β-naphthol in the presence of Nafion-H supported on silica-coated superparamagnetic iron oxide nanoparticles under microwave irradiation. The catalyst can be recovered easily and reused several times without significant loss of catalytic activity.

Hydroxylation of Benzene via C-H Activation Using Bimetallic CuAg@g-C3N4

Bimetallic CuAg@g-C₃N₄ catalyst system has been designed and synthesized by impregnating copper and silver nanoparticles over the graphitic carbon nitride surface. Its application has been demonstrated in the hydroxylation of benzene under visible light.

Investigation of Selective Microwave Heating Phenomena in the Reactions of 2-Substituted Pyridines

Debated selective microwave heating effects were investigated in a rearrangement and a benzylation reaction involving 2-substituted pyridines. An accurate, reproducible comparison technique and simultaneous temperature measurement using both external infrared and internal fibre optic sensors were utilized. The experimental details of the benzylation reaction were thoroughly addressed to resolve the inconsistencies that have been discussed previously in the literature. Hidden inhomogeneities in temperature and concentration were revealed within the reaction mixtures during microwave heating, which could be prevented by the modification of the vessel wall using an inert fluoropolymer liner. Instead of the previously proposed microscopic thermal microwave effect, the enhanced reaction rate could be explained by macroscopic-scale localized heating in the boundary layers close to the vessel surface in the microwave-heated experiment.

Chemoenzymatic one-pot reaction of noncompatible catalysts: combining enzymatic ester hydrolysis with Cu(i)/bipyridine catalyzed oxidation in aqueous medium

Combination of a lipase (CALB) with a Cu/bipyridine catalyst for environmentally benign synthesis of aldehydes from their corresponding esters.

Simple access toward 3-halo- and 3-nitro-pyrazolo[1,5-a]pyrimidines through a one-pot sequence

Herein, a regioselective, time-efficient and one-pot route for the synthesis of diversely substituted 3-halo- and 3-nitropyrazolo[1,5-a]pyrimidines in good to excellent yields through a microwave-assisted process is provided.

6-(Aryldiazenyl)pyrazolo[1,5-a]pyrimidines as Strategic Intermediates for the Synthesis of Pyrazolo[5,1-b]purines

A microwave-assisted approach for the regioselective synthesis of functionalized 6-(aryldiazenyl)pyrazolo[1,5-a]pyrimidin-7-amines from the cyclization of 3-oxo-2-(2-arylhydrazinylidene)butanenitriles with 5-amino-1H-pyrazoles under solvent-free conditions has been developed. This methodology was distinguished by its broad substrate scope, operational simplicity, high atom economy, and high-yielding without requiring chromatographic purification. In addition, an efficient and versatile palladium-catalyzed reductive azo cleavage is disclosed for the synthesis of diverse heteroaromatic 1,2-diamines, a valuable synthetic building block to develop new fused heteroaromatic systems. As synthetic example, several substituted pyrazolo[5,1-b]purines were synthesized in yields up to 96% by using microwave irradiation in the cyclocondensation of these 1,2-diamines with orthoesters.

Synthesis of Ag(II) 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin and its facile demetalation to 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin

A novel one-step strategy for the synthesis of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin using AgIIOBP is described. AgIIOBP was synthesized and was. Bromination of AgIITPP was carried out in a one-step reaction by varying the subsequently demetalated using H2S time interval and stoichiometric addition of Br2. The molecular weight of the halogenated porphyrin was confirmed by MALDI-TOF mass spectrometry. The synthesis of Ag(II) 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetraphenylporphyrin was followed by demetalation of Ag(II) ion from the halogenated porphyrin. The demetalation of was carried out under mild conditions using sodium sulphide in trifluoroacetic acid. The time taken for the demetalation was considerably lesser than previously reported and which facilitated a simple way for the isolation of the final product in good yield. The yield of the free base was 98%. The formation of the product and purity was confirmed by 1H NMR, Mass spectrometry. UV-visible spectrophotometer clearly showed the appearance of a characteristic Q-band of the octa-brominated porphyrin.

One-pot synthesis and in-vitro anticancer evaluation of 5-(2'-indolyl)thiazoles

A series of 5-(2′-indolyl)thiazoles were synthesized and evaluated for their cytotoxicity against selected human cancer cell lines. The reaction of thioamides 3 with 3-tosyloxypentane-2,4-dione 4 led to in situ formation of 5-acetylthiazole 5 which upon treatment with arylhydrazines 6 in polyphosphoric acid resulted in the formation of 5-(2′-indolyl)thiazoles 2. Among the synthesized 5-(2′-indolyl)thiazoles, compounds 2d–f, and 2h exhibited encouraging anticancer activity and also selectivity towards particular cell lines (IC₅₀ = 10–30 μM). Further studies on the SAR of compound 2e may result in good anticancer activity.

Design for carbon–carbon bond forming reactions under ambient conditions

The carbon–carbon (C–C) bond forms the ‘backbone’ of nearly every organic molecule, and lies at the heart of the chemical sciences! Let us explore designing of carbon–carbon frameworks at ambient conditions.

Microwave-assisted synthesis of 3-sulfenylindoles by sulfonyl hydrazides using organic ionic base-Brønsted acid

3-Sulfenylation of indoles by sulfonyl hydrazides using organic ionic base-Bronsted acid sulfonyl hydrazides as thiol surrogate.

Application of novel multi-cationic ionic liquids in microwave assisted 2-amino-4H-chromene synthesis

Novel multi-cationic ionic liquids containing a mesitylene backbone with acetate and methane sulphonate anions have been synthesized, and used for 2-amino-4H-chromene synthesis under MW.

Microwave-assisted heteropolyanion-based ionic liquid promoted sustainable protocol to N-heteroaryl amides via N-directing dual catalyzed oxidative amidation of aldehydes

A procedure for the synthesis of N-heteroaryl amides directly from oxidative amidation of aldehydes catalyzed by heteropolyanion-based ionic liquids has been reported. The proposed N-directing dual-catalysis mechanism was briefly investigated.

Alkyl group-directed assembly of coordination polymers based on bis-(4-imidazol-1-yl-phenyl)-amine and their photocatalytic properties

Four new coordination polymers have been solvothermally synthesized to explore their diverse networks and photocatalytic properties.

Superelectrophilic Activation of Crotonic/Methacrylic Acids: Direct Access to Thiochroman-4-ones from Benzenethiols by Microwave-Assisted One-Pot Alkylation/Cyclic Acylation

An efficient microwave-assisted protocol for the synthesis of 2-/3-methylthiochroman-4-ones by superacid-catalyzed alkylation followed by cyclic acylation (cyclization via intramolecular acylation) is described. Using easily accessible benzenethiols and crotonic acid/methacrylic acid with triflic acid (as catalyst of choice for needed optimal acidity), the reaction was tuned toward the formation of the cyclized products in good selectivity and yield. A mechanism involving the formation of carbenium-carboxonium superelectrophilic species is suggested.

Silica-Supported Oligomeric Benzyl Phosphate (Si-OBP) and Triazole Phosphate (Si-OTP) Alkylating Reagents

The syntheses of silica-supported oligomeric benzyl phosphates (Si-OBP(n)) and triazole phosphates (Si-OTP(n)) using ring-opening metathesis polymerization (ROMP) for use as efficient alkylating reagents is reported. Ease of synthesis and grafting onto the surface of norbornenyl-tagged (Nb-tagged) silica particles has been demonstrated for benzyl phosphate and triazole phosphate monomers. It is shown that these silica polymer hybrid reagents, Si-OBP(n) and Si-OTP(n), can be used to carry out alkylation reactions with an array of different nucleophiles to afford the corresponding benzylated and (triazolyl)methylated products in good yield and high purity.