Recyclable nanoparticulate copper mediated synthesis of naphthoxazinones in PEG-400: a green approach

Development of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates as heterogeneous catalysts for one pot synthesis of 1,2-dihydro-1-aryl-3H-naphth[1, 2-e][1,3]oxazin-3-one derivatives

Background:

Four members of N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates [DSTMG]n[X], where n= 1 or 2; X= FeCl4 - , Zn2Cl6 2-, NiCl4 2-, MnCl4 2- were synthesized as solid Brønsted-Lewis acidic compounds and studied the catalytic activity with the most acidic salt for three-component synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2- e][1,3]oxazin-3-ones.

Methods:

N,N-disulfo-1,1,3,3-tetramethylguanidinium chlorometallates of the four transition metal cations such as Fe(III), Zn(II), Ni(II) and Mn(II) were prepared after treatment of the parent ionic liquid N,N-disulfo-1,1,3,3- tetramethylguanidinium chloride [DSTMG][Cl] with the respective metal chlorides in different mole fractions at 75 ºC. The synthesis of 1,2-dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones was carried out via three-component reaction of 2-naphthol, aromatic aldehydes and urea under neat condition at 90 ºC using 7 mol% of the [DSTMG][FeCl4] catalyst.

Results:

The characterization of synthesized chlorometallates were done using spectroscopic and other analytical techniques including thermogravimetric analysis and Hammett acidity studies. Among the four salts, the salt of Fe(III) ion was observed as the strong Brønsted acidic hydrophobic salt and thus chosen for the catalytic study.

Conclusion:

A new type of chlorometallates of guanidinium cation with composition [DSTMG]n[X], where X= FeCl4 - /Zn2Cl6 2-/ NiCl4 2-/ MnCl4 2- and n= 1 or 2 were developed as –SO3H functionalized solid acids with varied thermal stability (150-250 ºC) and physisorbed water (0-20%) as observed from the thermogravimetric study. From them, the most Brønsted acidic Fe(III) salt was employed as efficient recyclable heterogeneous catalyst for the one-pot synthesis of 1,2- dihydro-1-aryl-3H-naphth[1,2-e][1,3]oxazin-3-ones in neat condition.

Recent development in the synthesis of heterocycles by 2-naphthol-based multicomponent reactions

2-Naphthol or β-naphthol is an important starting material that has drawn great attention in various organic transformations because of its attributes, such as low cost, easy to handle and eco-friendliness. The electron-rich aromatic framework of 2-naphthol with multiple reactive sites allows it to be utilized in several kinds of organic reactions eventuated to several organic molecules with potent biological properties. Multicomponent reaction approach has been tremendously utilized to explore the synthetic utility of 2-naphthol for the construction of diverse N/O-containing heterocyclic framework. In this review, we summarize recent data pertaining to multicomponent reactions, wherein heterocyclic compounds are synthesized utilizing 2-naphthol as one of the starting materials. It is anticipated that this review will stimulate the researchers to design new multicomponent strategies complying with the Green Chemistry principles for the further exploitation of 2-naphthol for the rapid synthesis of versatile biologically relevant heterocycles. This review provides a concise overview of the different 2-naphthol based multicomponent reactions utilized for the construction of diverse bioactive heterocyclic scaffold.

A PLA–TiO2 particle brush as a novel support for CuNPs: a catalyst for the fast sequential reduction and N-arylation of nitroarenes

One pot synthesis of diarylamines from nitro arenes by sequential reduction and N-arylation.

Manganese ferrite nanoparticle catalyzed tandem and green synthesis of spirooxindoles

PEG-400 as a nontoxic, green and reusable solvent was used for the synthesis of novel spiro-furo-pyridine-indoline-carbonitriles in the presence of a magnetically recoverable nanocatalyst.

A Facile One-Pot Solvent-Free Synthesis of 1,2-Dihydro-1-arylnaphtho[1,2-e][1,3]oxazine-3-ones Catalyzed by Wet Cyanuric Chloride

A novel one-pot synthesis of 1,2-dihydro-1-arylnaphtho[1,2-e][1,3]oxazine-3-ones by condensation of a variety of aldehydes withβ-naphthol and urea or thiourea in the presence of wet cyanuric chloride under solvent-free condition has been described. High yields, simple procedure, easy workup, short reaction times, and avoiding the use of organic solvent are the advantages of this green methodology.

Using hydrophilic ionic liquid, [bmim]BF4-ethylene glycol system as a novel media for the rapid synthesis of copper nanoparticles

In this work, we present a novel method for the synthesis of copper nanoparticles. We utilize the charge compensatory effect of ionic liquid [bmim]BF₄ in conjunction with ethylene glycol for providing electro-steric stabilization to copper nanoparticles prepared from copper sulphate using hydrazine hydrate as a reducing agent. The formed copper nanoparticles showed extended stability over a period of one year. Copper nanoparticles thus prepared were characterized by powder X-ray diffraction measurements (pXRD), transmission electron microscopy (TEM) and quasi elastic light scattering (QELS) techniques. Powder X-ray diffraction (pXRD) analysis revealed relevant Bragg's reflection for crystal structure of copper. Powder X-ray diffraction plots also revealed no oxidized material of copper nanoparticles. TEM showed nearly uniform distribution of the particles in methanol and confirmed by QELS. Typical applications of copper nanoparticles include uses in conductive films, lubrication and nanofluids. Currently efforts are under way in our laboratory for using these nanoparticles as catalysts for a variety of organic reactions.