Ring and side chain formylated pyrazoles from acetophenone azines and Vilsmeier's reagent

Differently substituted acetophenone azines on treatment with excess phosphorous oxychloride in N,N‐dimethylformamide have found to yield three products in each case. An acceptable mechanism has been suggested for the formation of all the three products. J. Heterocyclic Chem., (2011).     

Domino Vilsmeier-Haack/ring closure sequences: a facile synthesis of 3-chlorobenzo[b]thiophene-2-carbaldehydes

Vilsmeier’s reagent treatment of substituted diphenacyl sulfides or diphenacyl disulfides has led to the formation of a series of benzfused 3-chlorothiophene-2-carbaldehydes by a Domino Vilsmeier-Haack reaction/ring closure sequence, opening a new route for the synthesis of 3-chlorobenzo[b]thiophene-2-carbaldehydes and their benzfused analogues. A plausible mechanism has been proposed.     

A new method of synthesising (±)-thalictroidine and (±)-hygrine

A new route to synthesise (±)-thalictroidine and (±)-hygrine by tandem S_N2-Micheal reaction is described.     

Synthesis and conformation of diethyl 2,3‐diaryltetrahydro‐4,5‐isoxazoledicarboxylates

The microwave assisted synthesis of diethyl 2,3‐diaryltetrahydro‐4,5‐isoxazoledicarboxylates by the cycloaddition of diethyl maleate with appropriate nitrones was carried out. The conformational aspects of the title compounds were investigated by NMR and X‐ray studies and the features are compared with a set of related tetrahydroisoxazoles highlighting the effect of substituents on the conformation of central five mem‐bered ring.     

Identification and Structure Elucidation of a Novel Antifungal Compound Produced by Pseudomonas aeruginosa PGPR2 Against Macrophomina phaseolina

Pseudomonas aeruginosa PGPR2 was found to protect mungbean plants from charcoal rot disease caused by Macrophomina phaseolina. Secondary metabolites from the culture supernatant of P. aeruginosa PGPR2 were extracted with ethyl acetate and the antifungal compound was purified by preparative HPLC using reverse phase chromatography. The purified compound showed antifungal activity against M. phaseolina and other phytopathogenic fungi (Fusarium sp., Rhizoctonia sp. Alternaria sp., and Aspergillus sp.). The structure of the purified compound was determined using ¹H, ¹³C, 2D NMR spectra and liquid chromatography-mass spectrometry (LC-MS). Spectral data suggest that the antifungal compound is 3,4-dihydroxy-N-methyl-4-(4-oxochroman-2-yl)butanamide, with the chemical formula C₁₄H₁₇NO₅ and a molecular mass of 279. Though chemically synthesized chromanone derivatives have been shown to have antifungal activity, we report for the first time, the microbial production of a chromanone derivative with antifungal activity. This ability of P. aeruginosa PGPR2 makes it a suitable strain for biocontrol.     

Temperature‐Dependent Product Selectivity in the Vilsmeier?Haack Reaction on Bis(phenylhydrazones) of Bis(aroylmethyl) Sulfides (=1,1′‐[Thiobis(methylene)]bis[arylmethanone] Bis(2‐phenylhydrazones)): Synthesis of 3‐Aroylindoles (=Aryl(1H‐indol‐3‐yl)methanones)

The bis(phenylhydrazone) of substituted diphenacyl sulfides (=1,1′‐[thiobis(methylene)]bis[arylmethanone] bis(2‐phenylhydrazones)) 1 underwent a tandem sequence of reactions upon treatment with Vilsmeier reagent, ultimately yielding 3‐aroylindoles (=aryl(1H‐indol‐3‐yl)methanones) 3 (Scheme 1 and Table 1). The reaction seems to be product selective depending upon the reaction temperature.     

Synthesis of aligned hematite nanoparticles on chitosan–alginate films

Iron oxide nanoparticles are being viewed with interest owing to the great potential they have in the biomedical applications like MRI contrast enhancement, targeted drug delivery, hyperthermia and recently in magnetic separation of cancer cells from the body. Templated synthesis has been considered ideal for synthesis of iron oxide nanoparticles as particles are attracted magnetically, in addition to usual flocculation through van der Waals attraction. Biological templates are attractive owing to their biocompatibility and the attractive porosity and surface chemistry that nature provides. Polysaccharides like chitosan and alginate have been employed in the synthesis of a polyion complex, which provided the active-binding sites for iron(II) ions in solution to bind. The natural organization of chitosan and alginate into a porous film has been exploited to synthesize spherical iron oxide nanoparticles through careful calcination of the iron(II) conjugate film. Our experiments indicate that the formed nanoparticles are highly crystalline, confirm to the hematite structure and have a superparamagnetic response with a low coercivity of 116 Oe. Particles thus synthesized were highly monodisperse with hydrodynamic diameter of 1.8 nm. The symmetric porosity of the film translates into the synthesis of well-aligned nanoparticles of iron oxide. Compared to synthesis in solution, the film-assisted synthesis offered a greater degree of control over the particle size distribution pattern, with the chitosan–alginate template providing the needed spatial separation to prevent the aggregation due to magnetostatic coupling. Such hematite nanoparticles can either be used directly or converted to paramagnetic magnetite by reduction. Zeta potential measurements indicate highly stable nanoparticles, which can therefore be conjugated to cationic liposomes carrying drugs and magnetically guided to target sites.     

Synthesis and characterization of 4‐aryl‐5‐(1‐aryl‐2‐methyl‐2‐nitropropyl)‐1,2,3‐selenadiazoles

The synthesis of a new set of selenadiazoles, 4‐aryl‐5‐(1‐aryl‐2‐methyl‐2‐nitropropyl)‐1,2,3‐selenadiazoles ( 4 ) derived from 2‐[4‐methyl‐4‐nitro‐1,3‐diarylpentylidene]‐1‐hydrazinecarboxamide ( 3 ) has been reported. THF has been found to be the solvent of choice for this reaction. Structural features of 3 and 4 have been analyzed by NMR and X‐ray techniques.     

NMR investigation of hydrogen bonding and 1,3-tautomerism in 2-(2-hydroxy-5-substituted-aryl) benzimidazoles

The 1,3-tautomerism associated with 2-(2-hydroxy-5-substituted-aryl)benzimidazoles was studied in different solvents. The effect of hydrogen bonding involving the hydroxyl group of the 2-aryl ring on the tautomerism was investigated using NMR spectroscopy. The influence of the solvent concentration on 2-(2-hydroxy-5-chloroaryl)benzimidazole was studied in acetone-d6 and DMSO-d6.     

Synthesis of novel 3,5,7‐triaryl‐5,6‐dihydro‐4h‐1,2,5‐triazepines

Several hitherto unknown 3,5,7‐triaryl‐5,6‐dihydro‐4H‐1,2,5‐triazepines have been synthesised by cyclocondensation of N,N‐bis(phenacyl)anilines with hydrazine hydrate in ethanol or ethyleneglycol under reflux condition. Increased yields were obtained in the presence of p‐toluenesulfonic acid compared to the uncatalysed reaction.