S. M. S. Chauhan

Use of Graphite Oxide and Graphene Oxide as Catalysts in the Synthesis of Dipyrromethane and Calix(4)pyrrole

Graphite oxide and graphene oxides have been used as solid catalysts for the synthesis of 5,5-dialkyldipyrromethanes and calix[4]pyrroles in organic and aqueous solutions at room temperature.

Oxidation of 1-naphthol and related phenols with hydrogen peroxide and potassium superoxide catalysed by 5,10,15,20-tetraarylporphyrinatoiron(III)chlorides in different reaction conditions

Reaction of 1-naphthol and related phenols with hydrogen peroxide catalysed by 5,10,15,20-tetra(pentafluorophenyl)porphyrinatoiron(III)chloride gives corresponding quinones and oxidative phenol coupled products, whereas the reaction of naphthols with hydrogen peroxide catalysed by 5,10,15,20-tetramesitylporphyrinatoiron(III)chloride give above products along with quinone epoxides in moderate yields. The reaction of quinone with potassium superoxide catalysed by Me12TPPFe(III)Cl and p-MeOTPPFe(III)Cl give higher yields of quinone epoxides than the reaction of quinone with hydrogen peroxide catalysed by 5,10,15,20-tetraarylporphyrinatoiron(III)chlorides.

Facile and Efficient Synthesis of 14‐Alkyl‐ or Aryl‐14‐H‐Dibenzo[a,j]xanthenes using Sulfonyl‐Functionalized Ionic Liquids

Abstract An efficient, simple, and rapid synthesis of 14‐alkyl‐or aryl‐14‐H‐dibenzo[a,j]xanthenes is reported by one‐pot condensation of 2‐naphthol with alkyl or aryl aldehydes in the presence of sulfonyl‐functionalized acidic ionic liquids at 125°C.

Activity-guided isolation of antioxidant xanthones from Swertia chirayita (Roxb.) H. Karsten (Gentianaceae)

An activity-guided isolation and purification process was used to identify the DPPH (l,l-diphenyl-2-picrylhydrazyl) radical-scavenging components of Swertia chirayita. A dry, whole plant of S. chirayita was extracted with different solvents and tested for its DPPH radical-scavenging activity. The acetone : water (8 : 2) extract showed the highest total phenolic content (TPC) and DPPH radical-scavenging activity, which was column chromatographed to obtain decussatin, swertianin, bellidifolin, isobellidifolin, amarogentin, swertianolin and mangiferin as active components. Good correlation was observed between TPC and DPPH scavenging activity among the extracts. The unique structure of xanthones, including the catecholic moiety and the completely conjugated system, enables them to be promising antioxidants.

Synthesis and anion binding properties of novel 3,12- and 3,7-bis(4′-nitrophenyl)-azo-calix[4]pyrrole receptors

Two novel 3,12- and 3,7-bis(4′-nitrophenyl)-azo-5,5,10,10,15,15,20,20-octamethyl calix[4]pyrroles were prepared and studied as potential anion binders for AcO− and H2PO4−; the isomeric pair not only allowed for the colorimetric detection but also helped to discriminate the geometrically different anions.

Syntheses of Calix[4]Pyrroles by Amberlyst-15 Catalyzed Cyclocondensations of Pyrrole with Selected Ketones

A facile and efficient protocol is reported for the synthesis of calix[4]pyrroles and N-confused calix[4]pyrroles in moderate to excellent yields by reaction of dialkyl or cycloalkyl ketones with pyrrole catalyzed by reusable Amberlyst(TM)-15 under eco-friendly conditions.

Microwave assisted dealkylation of alkyl aryl ethers in ionic liquids

Alkyl aryl ethers undergo selective dealkylation in 1-butyl pyridinium bromide and 1-butyl-3-methyl imidazolium bromide ionic liquids under microwave irradiation to give the corresponding phenols in high yields. The ionic liquids serve the dual purpose of solvent as well as reagent and allow easy isolation of products.

Copper (I) chloride catalyzed synthesis of diaryl ethers in ionic liquids under mild conditions

Abstract The reaction of different aryl halides with aryl oxides catalyzed by CuCl in 1-butyl-3-methyl-imidazolium tetrafluoroborate [bmim][BF4] and 1-butyl-3-methyl-imidazolium hexafluorophosphate [bmim][PF6] ionic liquids to give diaryl ethers in 54–90% yields has been studied under mild reaction conditions.

Chemoselective Esterification of Phenolic Acids in the Presence of Sodium Bicarbonate in Ionic Liquids

Abstract Chemoselective esterification of phenolic acids with dialkyl sulphates or alkyl halides in the presence of sodium bicarbonate in 1,3‐dialkylimidazolium ionic liquids is reported in excellent yields and less reaction time as compared to organic solvents.

Synthesis and anion binding of 2-arylazo-meso-octamethylcalix[4]pyrroles

2-Arylazo-5,5,10,10,15,15,20,20-octamethylcalix[4]pyrroles (azo-OMCPs) have been synthesised by the reaction of calix[4]pyrrole with aryldiazonium chloride in 15–45% yields. The solution-state binding studies of the synthesised hosts were investigated by absorption spectroscopy and 1H NMR in DMSO and CDCl3, respectively. These receptors, appended with electron-donating and electron-withdrawing groups, displayed enhanced affinity and selectivity for fluoride anion. Well-defined colour change in the visible region of the spectrum was observed upon addition of fluoride ion in DMSO solution of azo-OMCPs. Detailed NMR studies in CDCl3 revealed that azo-OMCPs with nitro and chloro groups have higher binding affinity for fluoride ion.