New cup-shaped α-cyclodextrin derivatives and a study of their catalytic properties in oxidation reactions

A series of new α-cyclodextrin derivatives with a substituted propylene bridge attached to the 6-O's of the A,D-glucose units are reported. The compounds were prepared from the known 6^A,6^D-di-O-(prop-2-methylidene-1,3-dienyl)-hexadeca-O-benzyl-α-cyclodextrin, which was transformed into 6^A,6^D-di-O-(prop-2-methyl-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-formyl-2-hydroxy-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-aminomethyl-2-hydroxy-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-hydroxymethylidene-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-formyl-1,3-dienyl)-α-cyclodextrin, 6^A,6^D-di-O-(prop-2-carboxy-1,3-dienyl)-α-cyclodextrin and 6^A,6^D-di-O-(prop-2-methoxycarbonyl-1,3-dienyl)-α-cyclodextrin. The new compounds were evaluated for their ability to affect amine and alcohol oxidations in the presence of hydrogen peroxide.     

Supramolecular oxidation of anilines using hydrogen peroxide as stoichiometric oxidant

6A,6D-Di-O-(propan-2-on-1,3-diyl) alpha-cyclodextrin-6A,6D-dicarboxylate (2alpha) and 6A,6D-di-O-(propan-2-on-1,3-diyl) beta-cyclodextrin-6A,6D-dicarboxylate (2beta) were found to catalyze the oxidation of aromatic amines in the presence of hydrogen peroxide. The products were the corresponding nitro compounds or in some cases azo-, azoxy-, or other dimerization products. The catalysis was found to follow enzyme kinetics giving a rate increase (kcat/kuncat) of up to 1100 in the best case.     

Comparative study of some synthesised and commercial fluorogenic substrates for horseradish peroxidase and its mimetic enzyme hemin by a flow injection method

Four 3,4-dihydroquinoxalin-2(1H)-one derivatives, i.e., 3,4-dihydroquinoxalin-2(lH)-one (DHQ), 3-methyl-3,4-dihydroquinoxalin-2(1H)-one (MDHQ), 3,4-dihydroquinoxalin-2(1H)-one-6-acid (DHQ-6-A) and 3-methyl-3,4-dihydroquinoxalin-2(1H)-one-6-acid (MDHQ-6-A), and N,N′-dicyanomethyl-o-phenylenediamine (DCM-OPA) were synthesised as potential substrates for horseradish peroxidase (HRP). Of these compounds DCM-OPA, DHQ and MDHQ can be prepared by very simple methods in a pure form in large quantities. Their properties for use as fluorogenic substrates for HRP and its mimetic enzyme hemin were compared with commercially available substrates, i.e., p-hydroxyphenylacetic acid (p-HPA), p-hydroxyphenylpropionic acid (p-HPPA), homovanillic acid (HVA) and tyramine, by a flow injection method. The results showed that DCM-OPA and MDHQ were the best among the five synthesised substrates and p-HPPA and p-HPA are better than HVA and tyramine. Substrates p-HPPA, p-HPA, DCM-OPA and MDHQ showed comparable ability for H₂O₂ detection in HRP and hemin catalysed reaction systems, with detection limits in the nmol l⁻¹ region. The stability of DCM-OPA is better than MDHQ, but both are stable for at least a month in a refrigerator.     

13C NMR spectra of some 1,2-disubstitutedN-vinyl-1H-1,2,4-triazoles

¹³C NMR spectra (20 and 75 MHz, in DMSO-d₆) of a series of 1,3-diaryl-3-(1H-1,2,4-triazol-1-yl)- and 1,3-diaryl-2-(1H-1,2,4-triazol-1-yl)prop-2-en-1-ones were registered. It was shown that the chemical shifts of both the carbon atom of the alkene group and C(3) reflect regio- and stereoisomerism of these compounds. Taking this into account the isomeric structures of several 1,3-diaryl-3-(1H-1,2,4-triazol-1-yl)prop-2-en-1-ones were identified and the configurations relative to the double bond of a number of 1,3-diaryl-2-(1H-1,2,4-triazol-1-yl)prop-2-en-1-ones were determined.     

Polyimides with main-chain photosensitive groups: Synthesis, characterization and their properties as liquid crystal alignment layers

In this work, a series of polyimides containing main-chain chalcone groups and side-chain cinnamate or acetate groups were synthesized. In the synthetic route, three dianhydride monomers were prepared by the reactions of 1,3-dihydro-1,3-dioxoisobenzofuran-5-carbonyl chloride with 1,3-bis(4-hydroxylphenyl)prop-2-en-1-one, 1,3-bis(4-(2-hydroxyethyl)phenyl)prop-2-en-1-one, and 1,3-bis(4-hydroxyphenyl)-pent-1-en-3-one-4-en, respectively. The precursor polyimides were obtained by the polycondensation of the dianhydride monomers with 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane and the in situ imidization. After the polymerization, the final products were obtained by introducing the side groups through the reactions of the polyimide precursors with cinnamoyl chloride or acetic anhydride. The chemical structures and properties of the polyimides were characterized by elemental analysis, ¹H NMR, ¹³C NMR, FTIR, GPC, and thermal analysis. The polyimides show high thermal stability and good solubility in aprotic polar organic solvents. The polyimides can undergo sensitive [2+2] photocycloaddition reaction upon the UV light irradiation. After irradiation with linearly polarized UV light, the polyimide thin films can induce 5CB liquid crystal molecules to homogeneously align in the liquid crystal cells. Both the alignment ability and pretilt angles of the molecular orientation depend on the chemical structures of the polyimides.     

Electrochromic tetrathiafulvalene derivatives functionalised with 2,5-diaryl-1,3,4-oxadiazole chromophores

Electrochromism has been demonstrated by three novel electrochemically-reversible compounds and, which were synthesised by Pd catalysed cross-coupling of iodotrimethylTTF (6) and 2,6(7)-diiodoTTF (7) with the 2,5-diaryl-1,3,4-oxadiazole derivatives 1 and 2 containing terminal ethyne and butadiyne groups.     

Nitrate and perchlorate salts of a silver(I) complex from 5-methyl-2-(2,3-diaza-4-(5-methyl-2-thienyl)buta-1,3-dienyl)thiophene

Bis(5-methyl-2-(2,3-diaza-4-(5-methyl-2-thienyl)buta-1,3-dienyl)thiophene) silver(I) complex was synthesized in high yield by refluxing 5-methyl-2-(2,3-diaza-4-(5-methyl-2-thienyl)buta-1,3-dienyl)thiophene (L) with silver nitrate or silver perchlorate in anhydrous acetonitrile. The product thus formed was well characterized by NMR, IR, UV–Vis and mass spectroscopies as well as elemental analysis and electrochemical analysis. Molecular structures of compounds L, [L₂Ag]NO₃ and [L₂Ag]ClO₄ were determined by single crystal X-ray diffraction analysis. It was found that the C=N double bond of the ligand rotated during the course of ligand coordination in the case of the perchlorate salt but not in the case of the nitrate salt.     

Influence of trimethoxy-substituted positions on fluorescence of heteroaryl chalcone derivatives

Three series of heteroaryl chalcones, (E)-1-(2-pyridyl)-3-(X)prop-2-en-1-one (Ia-Ic), (E)-1-(2-thienyl)-3-(X)prop-2-en-1-one (IIa-IIc), and (E)-1-(2-furyl)-3-(X)prop-2-en-1-one (IIIa-IIIc), where X = 2,4,5-trimethoxyphenyl (for series a), X = 2,4,6-trimethoxyphenyl (for series b), and X = 3,4,5-trimethoxyphenyl (for series c) were synthesised using basic catalysed aldol condensation and characterised using 1H NMR and FT-IR spectroscopies. Compound IIa was also characterised by single crystal X-ray analysis. The absorption and fluorescence emission spectra of these compounds revealed that the absorption and fluorescence depended on the heterocycle rings and trimethoxysubstituted phenyl rings linked to the enone system. The position of methoxy groups substantially affected the fluorescent properties. Compounds Ia-IIIa containing the 2,4,5-trimethoxyphenyl moiety exhibited the red-shift phenomenon and strong emission fluorescence.     

Prenylindoles from Tanzanian Monodora and Isolona species

6-(3-Methyl-but-2-enyl)-1,3-dihydro-indol-2-one, annonidine F [3-[6-(3-methyl-but-2-enyl)-1H-indolyl]-6-(3-methyl-but-2-enyl)-1H-indole], 1H-indole-5-carbaldehyde, 6-(3-methyl-2-butenyl)-1H-indole, 6-(3-methyl-buta-1,3-dienyl)-1H-indole, 6-(4-oxo-but-2-enyl)-1H-indole and 3-geranylindole were isolated from Monodora angolensis (Annonaceae) while 3-(1,1-dimethyl-but-2-enyl)-5-(3-methyl-but-2-enyl)-1H-indole (caulidine A), 4-[3-(1,1-dimethyl-but-2-enyl)-1H-indol-5-yl]-but-3-en-2-one (caulidine B), 5-(3-methyl-2-butenyl)-1H-indole and 5-(3-methylbuta-1,3-dienyl)-1H-indole were obtained from Isolona cauliflora (Annonaceae); structural determination by spectroscopic analysis. Some of the prenylindoles had antifungal and antimalarial activities.     

Epoxidation of propyl- and isobutyl-β-alkylvinylketones

A study is made of the epoxidation of hepten-2-one-4, octen-3-one-5, nonen-4-one-6, 2-methylhepten-5-one-4, 2-methylocten-5-one-4, and 2-methylnonen-5-one-4 with alkaline methanolic hydrogen peroxide. 46–71% yield of the corresponding epoxy ketones are obtained. It is shown that treatment of the 2, 3-epoxyheptanone-4, 3, 4-epoxyoctanone-5, 4, 5-epoxynonanone-6, 2-methyl-5, 6-epoxyheptanone-4, 2-methyl-5, 6-epoxyoctanone-4 and 2-methyl-5, 6-epoxynonanone-4 with zinc chloride isomerizes them to, respectively, heptandione-3, 4, octandione-4, 5, nonandione-4, 5, 2-methylheptandione-4, 5, 2-methyloctandione-4, 5, and 2-methylnonandione-4, 5 in upto 78% yield.     

Highly diastereoselective intramolecular Diels-Alder reaction of chiral silatrienes

New Si-chiral 2-silahexa-3,5-dienyl acrylates were prepared in six steps from dichloro(chloromethyl)methylsilane. The EtAlCl₂ catalysed intramolecular Diels-Alder reaction of these compounds gave chiral 4-sila-4a,7,8,8a-tetrahydroisochroman-1-ones in good yield. Very good diastereoselectivity was observed for a silatriene bearing a methyl and a 2-methoxyphenyl substituent on the chiral silicon atom.     

Synthesis and characterization of some chalcones and their cyclohexenone derivatives

A series of chalcones and their derivatives have been synthesized. Chalcones, 1-(1,3-benzodioxol-5-yl)-3-(aryl)-prop-2-en-1-ones were prepared by the aldol condensation of 1-(1,3-benzodioxol-5-yl)ethanones and aryl aldehydes. Based-catalyzed condensation of 1-(1,3-benzodioxol-5-yl)-3-(aryl)prop-2-en-1-ones with ethyl acetoacetate yields corresponding ethyl 4-(1,3-benzodioxol-5-yl)-6-(aryl)-2-oxocyclohex-3-ene-1-carboxylates. Some of the synthesized chalcones were reported in the literature; the newly synthesized compounds were characterized by single crystal X-ray studies, IR, ¹H-NMR and LCMS mass spectral analysis.     

Synthesis of 6-(perfluoroalkyl)salicylates by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 3-ethoxy-1-(perfluoroalkyl)prop-2-en-1-ones

6-(Perfluoroalkyl)salicylates were prepared by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 3-ethoxy-1-(perfluoroalkyl)prop-2-en-1-ones.     

A new eco-friendly strategy for the synthesis of novel antimicrobial spiro-oxindole derivatives via supramolecular catalysis

Novel spiro-oxindole derivatives were synthesised by one-pot multicomponent reaction using isatins, urea and 1,3-dicarbonyls. β-Cyclodextrin, an oligosaccharide, catalysed the reaction and can be reused for further reaction after recovery. This developed synthetic route is environmentally benign in which water is used as solvent to produce excellent yields of products. The synthesised compounds were evaluated for their antimicrobial activities against two bacteria and two fungi. All the synthesised spiro-oxindoles exhibit significant antimicrobial activity.     

Regioselective synthesis of 4-alkyl- and 4-aryl-6-(perfluoroalkyl)salicylic acid derivatives by formal [3+3] cyclocondensation of 1,3-bis(silyloxy)-1,3-butadienes with 3-silyloxy-1-(perfluoroalkyl)prop-2-en-1-ones

4-Alkyl- and 4-aryl-6-(perfluoroalkyl)salicylic acid derivatives were regioselectively prepared by [3+3] cyclization of 1,3-bis(silyl enol ethers) with 3-silyloxy-1-(perfluoroalkyl)prop-2-en-1-ones.     

Fischer iondolization and its related compounds—X: Application of the advanced fischer indolization of a 2-methoxyphenylhydrazone derivative to syntheses of some naturally occurring 6-substituted indoles

Two naturally occurring 6-substituted indoles, 6-(3-methylbuta-1,3-dienyl)indole (2) and 6-(3-methyl-2-butenyl)indole (5), were synthesized by using an advanced Fischer indolization of a 2-methoxyphenylhydrazone derivative.     

Diels-Alder cycloaddition of electrophilic 2H-azirines with 3-(3-(tert-butyldimethylsilyloxy)buta-1,3-dienyl)oxazolidin-2-ones. Treatment of the cycloadducts under acidic conditions

3-(3-(tert-Butyldimethylsilyloxy)buta-1,3-dienyl)oxazolidin-2-one was reacted with several electrophilic 2H-azirines to give the expected cycloadducts in moderate to good yields. Treatment of the cycloadducts under acidic conditions gave six-membered ring aminoenones and aziridine derivatives. In the case where anilinium fluoride was used an inversion at the C-2 stereogenic center was observed forming an isomer of the former cycloadduct. The chiral (R)-3-(3-(tert-butyldimethylsiloxy)buta-1,3-dienyl)-4-phenyloxazolidin-2-one was also reacted with an electrophilic 2H-azirine. The reaction showed no diastereoselectivity, but both diastereoisomers were fully isolated by chromatography.     

Functionalisation reactions of 2,5-diphenyl-1,3,4-oxadiazoles bearing a terminal ethynyl or butadiynyl substituent: X-ray crystal structures of the products

2-(4-tert-Butylphenyl)-5-(4-ethynylphenyl)-1,3,4-oxadiazole 1 and the butadiyne analogue 2 reacted with triethyl orthoformate in the presence of zinc iodide to give the acetal derivatives 3 and 4 which were hydrolysed with Amberlyst-15 in acetone-water to afford the alkynylaldehyde derivatives 5 and 6 in high yields. The reaction of 4,5-bis(methoxycarbonyl)-2-tributylphosphonium-1,3-dithiole tetrafluoroborate 7 salt with 5(nBuLi, THF) gave the Wittig product 2-(3-[4-[5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]phenyl]prop-2-ynylidene)-1,3-dithiole-4,5-dimethyl dicarboxylate 11 (33% yield) whereas other attempted Wittig and Horner-Wadsworth-Emmons reactions led to the unexpected loss of the aldehyde group from compounds 5 and 6 to give 1 and 2, respectively. The X-ray crystal structures of compounds, 3, 4, 5 and 11 are reported: the pi-systems of all four molecules adopt predominantly planar conformations. A comparison of bond lengths in the structures of 5 and 11 reveals extended pi-conjugation in the latter.     

Intramolecular gold(III) catalysed Diels–Alder reaction of 1-(2-furyl)-hex-1-en-5-yn-3-ol derivatives: a short and generalised route for the synthesis of hydroxyphenanthrene derivatives

Gold(III) catalysed intramolecular Diels–Alder reaction of various 1-(2-furyl)-hex-1-en-5-yn-3-ol derivatives has been studied to synthesise hydroxyphenanthrenes and other polynuclear aromatic hydroxyl compounds. The required precursors were synthesised by indium mediated propargylation of suitable β-furyl-α,β-unsaturated aldehydes.     

Spectral correlation,antimicrobial and insect antifeedant activities of some 1-naphthyl keto-oxiranes

Thirteen optically active (αS, βR) 1-naphthyl keto-oxiranes (1-naphthyl-4-yl[3-(substituted phenyl)oxiran-2-yl]methanones) have been synthesised by phase transfer catalysed epoxidation of 1-naphthyl chalcones. The yields of oxiranes are more than 95%. The synthesized oxiranes have been characterized by IR, ¹H, ¹³C and MS spectra. The spectral data are correlated with Hammett substituent constants and Swain–Lupton parameters. From the regression analysis the effect of substituent on the group frequencies has been predicted. The antimicrobial and insect antifeedant activities of all synthesised oxiranes have been evaluated.