Katalytische isomerisierung von heptenen mit IrX(CO)L2

1-, 2-cis-, 2-trans-, and 3-trans-heptenes (C₇)are isomerized either very slowly or not at all with IrX(CO)L₂ at 80°C in toluene and under N₂. However, under the conditions of hydrogenation fast isomerisation takes place. With IrCl(CO)L₂ as catalyst the rate of isomerisation decreases the order: 1-C₇ ∼ 2-cis-C₇ > 3-trans-C₇ > 2-trans-C₇. This sequence is independent of the ligand L in lrCl(CO)L₂, however, with a particular isomer the rate of isomerisation is a function of L in the order L = PPh₃ > P(C₆H₁₁)3 > P(OPh)₃.     

Domino Diels-Alder reactions of N-methoxyethyl-7-oxa-norbornadiene-2,3-dicarboximide: an elusive, highly reactive dienophile

Flash vacuum pyrolysis (FVP) has been used to generate the novel 7-oxa-norbornadiene-2,3-dicarboxylic imide that in situ gave an unprecedented cycloaddition reaction cascade with the imidofuran, a side-product of FVP. Stereoselectivity of cycloadditions was studied with the aid of density functional calculations, which fully support observed exo/endo-selectivity.     

Stereoselectivity in the epoxidation of carbohydrate-based oxepines

The facial selectivity in the DMDO epoxidation of carbohydrate-based oxepines derived from glucose, galactose, and mannose has been determined by product analysis and density functional theory (DFT, B3LYP/6-31+G**//B3LYP/6-31G*) calculations. Oxepines 3 and 4, derived from d-galactose and d-mannose, largely favor alpha- over beta-epoxidation. The results reported here, along with selectivities in the DMDO-mediated epoxidation of d-xylose-based oxepine 1 and d-glucose-based oxepines 2 and 5 reported earlier, support a model in which electronic effects, guided by the stereochemistry of the oxygens on the oxepine ring, largely determine the stereoselectivity of epoxidation. Other contributing factors included conformational issues in the oxepine's transition state relative to the reactant, the asynchronicity in bond formation of the epoxide, and the overall steric bulk on the alpha- and beta-faces of the oxepine. Considered together, these factors should generally predict facial selectivity in the DMDO-epoxidation of cyclic enol ethers.     

Synthesis and properties of (E)-1,2-difluoroethylene derivatives: improvement of the ultraviolet light stability

The synthesis and properties of (E)-α,β-difluorostilbene derivatives were studied. In particular, we investigated three suppression methods of (E)–(Z) isomerisation by shortening the molecular conjugation length, which included the introduction of a fluorine atom into the ortho or para position of the benzene ring or the replacement of the benzene ring with a cyclohexane ring. The relationship between the molecular structure of liquid crystals and the level of isomerisation by ultraviolet (UV) light was discussed.     

Catalyse multifonctionnelle—VI : Isomerisation de la Δ-5 cholestenone par les melanges phenols-amines

Kinetic study of Δ-5 cholestenone isomerisation in benzene, catalysed by phenols-triethylamine mixtures indicates a transition state with a mole of phenol and a phenol-triethylamine complex. Catalytic activity of phenols-triethylamine mixtures according to versus those complexes association constants in benzene shows a clear maximum for m-nitrophenol. Besides, activation enthalpies are decreasing with phenols acidities, while activation entropies become more negative.     

Flash vacuum pyrolysis of azo and nitrosophenols: new routes towards hydroxyarylnitrenes and their reactions

Flash vacuum pyrolysis of phenylazonaphthols and nitrosonaphthols at 700°C and 0.02 Torr yielded quinoline, isoquinoline, indene and naphthols (and aniline only from the phenylazo derivatives). Similar FVP of p-nitroso and p-phenylazophenol gave pyridine. Also, FVP of phenanthraquinonemonophenylhydrazone and monooxime gave phenathridine and fluorenone. The formation of the heterocyclic system was assumed to involve nitrene and azatropone intermediates.     

Reaction of tetracyanoethene with tricarbonyliron complexes of some substituted 7-methylenecycloheptatrienes and the subsequent isomerization of the initial addition products

An NMR study of tetracyanoethene (tcne) addition to substituted (η⁴-7-methylenecycloheptatriene)Fe(CO)₃ complexes shows that 1,3-addition is the dominant initial reaction. Subsequent isomerisation of these 1,3-adducts to 1,6- or 1,8-adducts is controlled by steric factors. Frontier orbital analyses allow concerted pathways to be identified for each observed addition and isomerisation. The crystal structure of the tcne adduct of (η⁴-7-phenylmethylenecycloheptatriene)Fe(CO)₃ establishes an exo geometry for the phenyl substituent.     

Flash vacuum pyrolysis of N-phenylbenzamide oxime and related compounds

Flash vacuum pyrolysis (FVP) of the benzamide oxime 1 at 650 °C leads to the imino-oxadiazole 10 as the major product. It is probably formed by intermolecular cycloaddition of benzonitrile oxide 11 and the diphenylcarbodiimide 12, an unexpected process to take place under FVP conditions. Intermediates 11 and 12 are themselves obtained by competitive dehydration and elimination of aniline from 1. Mixed products were obtained from FVP of the C- and N-p-tolyl analogues of 1 (5 and 6, respectively) probably owing to equilibration of the carbodiimide intermediate.     

Studies in trifluoromethaneslphonic acid—I: Protonation of aromatic derivatives

Solutions of aromatic compounds in trifluoromethanesulphonic acid have been investigated using ¹H-NMR and UV specstrocpy. In addition, conductivity measurements were made over a wide concentration range. At low concentrations ( < 0.001M) all derivatives were completely protonated. For 0.2-1.0M evidence was obtained for ion pairing in the cases of benzene and toluene. An intimate ion pair is postulated in which the partial charges on the arenium ion and on the sulphonate anion match up to maximise electrostatic interaction. The stability of these two species is discussed for a series of methylbenzenes.Exchange reactions are also discussed in terms of ion pairing. Preliminary results show that both trans alkylation and isomerisation reactions occur with great facility in this solvent. Dihydroanthreacene undergoes a disproportionation reaction in which it acts as a very powerful hydride donor.     

Constituents of the Leaves and Stem Bark of Aglaia foveolata

The previously known potent cytotoxic agent silvestrol (1) (0.002% w/w yield) and five new flavagline derivatives (2-6) were isolated from the leaves of Aglaia foveolata collected in Indonesia. The new compound 5 has an unprecedented cyclic amide moiety in its cyclopenta[b]benzopyran skeleton, while compound 6 is a novel benzo[b]oxepine derivative in which the oxepine ring is cleaved. Pyramidatine (7), a biogenetic precursor of the new flavaglines 2-6, was isolated from the leaf extract investigated. Silvestrol was also isolated from the stem bark of A. foveolata (yield of 0.02% w/w) along with a new baccharane-type triterpenoid (8). The structures of the new compounds were elucidated on the basis of their NMR and mass spectrometric data. All new compounds isolated were tested against a panel of cancer cell lines, but only compound 2 was cytotoxic (IC₅₀ range=1.4-1.8 μM), and is the first member of the cyclopenta[b]benzopyran class found to exhibit this type of activity. Compound 2 also showed significant NF-κB inhibitory activity in an Elisa assay (IC₅₀=0.37 μM).     

Synthesis and Study of Dibenzo[b,f]oxepine Combined with Fluoroazobenzenes—New Photoswitches for Application in Biological Systems

Dibenzo[b, f]oxepine derivatives are an important scaffold in natural, medicinal chemistry, and these derivatives occur in several medicinally relevant plants. Two dibenzo[b, f]oxepines were selected and connected with appropriate fluorine azobenzenes. In the next step, the geometry of E/Z isomers was analyzed using density functional theory (DFT) calculations. Then the energies of the HOMO and LUMO orbitals were calculated for the E/Z isomers to determine the HOMO-LUMO gap. Next, modeling of the interaction between the obtained isomers of the compounds and the colchicine α and β-tubulin binding site was performed. The investigated isomers interact with the colchicine binding site in tubulin with a part of the dibenzo[b, f]oxepine or in a part of the azo switch, or both at the same time. Based on the UV-VIS spectra, it was found that in the case of compounds with an azo bond in the meta position, the absorption bands n→π* for both geometric isomers and their separation from π→π* are visible. These derivatives therefore have the potential to be used in photopharmacology.     

广东石豆兰中的噁庚英和联苄类化合物

从兰科植物广东石豆兰(Bulbophyllum kwangtungense Schlecht.)的乙酸乙酯部分分离得到了2个新的茋类化合物5-(2,3-二甲氧苯乙基)-6-甲基苯并[d][1,3]二氧戊环(1)和10,11-二氢-2,7-二甲氧基-3,4-亚甲二氧基二苯并[b,f]噁庚英(2). 药理活性实验结果证明, 化合物2对体外培养的Hela细胞有较强的抑制作用.     

Concise total syntheses of heliannuols B and D

Concise and efficient enantioselective total syntheses of heliannuols B and D have been accomplished using chirality transfer through a Lewis acid-promoted Claisen rearrangement for the construction of the C7 tertiary stereogenic center and a relay ring-closing metathesis for assembling the dihydrobenzo[b]oxepine backbone of the natural products as the key steps.     

Characterization,Antioxidant and Anti-Inflammation Capacities of Fermented Flammulina velutipes Polyphenols

This work investigated the preparation, characterization, antioxidant, and anti-inflammation capacities of Flammulina velutipes polyphenols (FVP) and fermented FVP (FFVP). The results revealed that the new syringic acid, accounting for 22.22%, was obtained after fermentation (FFVP). FFVP exhibits higher antioxidant and anti-inflammation activities than FVP, enhancing cell viability and phagocytosis, inhibiting the secretion of NO and ROS, and reducing the inflammatory response of RAW264.7 cells. This study revealed that FFVP provides a theoretical reference for in-depth study of its regulatory mechanisms and further development of functional antioxidants that are applicable in the food and health industry.     

Gas-phase thermolysis of 1-acylnaphtho[1,8-de][1,2,3]triazines. Interesting direct routes towards condensed naphtho[1,8-de]heterocyclic ring systems

FVP pyrolysis of 1-acylnaphtho[1,8-de][1,2,3]triazines at 500 °C and 10⁻² Torr gave exclusively the corresponding 2-substituted naphtho[1,8-de][1,3]oxazines. The latter was also obtained by static pyrolysis but in lower yield along with the corresponding N-(naphthalen-1-yl)acylamides. The reaction was studied kinetically and mechanistically.     

Photo-curing kinetics for the UV-initiated cationic polymerization of a cycloaliphatic diepoxide system photosensitized by thioxanthone

Photo-differential scanning calorimetry (photo-DSC) was used to investigate the cure kinetics for the UV-initiated cationic photo-polymerization of cycloaliphatic diepoxide (CADE) systems with and without a photo-sensitizer, 2,4-diethylthioxanthone (DETX), in the presence of a diaryliodonium-salt photo-initiator. Two kinetics parameters—the rate constant (k) and the order of the initiation reaction (m)—were determined for the CADE epoxide system for different amounts of added DETX photo-sensitizer (0-1 wt%) and at different isothermal temperatures (25-100 °C) using an autocatalytic kinetics model. The photo-sensitized CADE epoxide system gave much higher k and m values than the nonphoto-sensitized one (due to the photo-sensitization effect). Moreover, k and m for both CADE epoxide systems with and without DETX increased significantly with increasing isothermal temperature due to a thermal contribution towards increasing the mobility of active species. We also observed that the addition of DETX lowered the activation energy for the UV-curable epoxide system; the collision factor for the system with DETX was higher than that obtained for the system without DETX, indicating that the reactivity of the former was greater than that of the latter due to the photo-sensitization effect.     

A highly regio- and stereoselective nickel-catalyzed ring-opening reaction of alkyl- and allylzirconium reagents to 7-oxabenzonorbornadienes

[Reaction: see text]. An efficient method for the synthesis of cis-2-alkyl- or allyl-1,2-dihydronaphthalenes via a nickel-catalyzed highly regio- and stereoselective ring-opening addition of alkyl- or allylzirconium reagents to 7-oxabenzonorbornadienes is described. Treatment of 7-oxabenzonorbornadienes 1a-c with various alkylzirconium reagents 2a-j (Cp2ZrClCH2CH2R: R = tert-butyl, n-butyl, n-pentyl, -(CH2)3CH=C(CH3)2, -SiMe3, -CH2SiMe3, -(CH2)3Br, cyclopentyl, cyclohexyl, and benzyl) in the presence of NiBr2(dppe) and Zn powder in dry THF at 50 degrees C afforded the corresponding cis-2-alkyl-1,2-dihydronaphthalene derivatives 3a-m in good yields. In addition, allyl zirconium reagents 4a-c also underwent ring-opening reactions with 1a and 1c to give 5a-d in very good yields. The alkylative ring-opening products from 7-oxabenzonorbornadiene can be further converted to naphthalene derivatives 6a-c, via an acid-mediated dehydration, in good to excellent yields. A possible mechanism for the present catalytic reaction was proposed.     

Molecular weight and configurational stability of poly(phenylacetylene) prepared with Rh catalyst

High-cis poly(phenylacetylene) (PPhA) has been prepared by polymerization of phenylacetylene with [Rh(COD)acac] catalyst and its molecular weight (MW) and configurational stability studied by SEC, ¹H NMR, UV/vis and IR techniques. PPhA dissolved in THF and THF-d₈ and exposed to the atmosphere and daylight at room temperature was found to undergo simultaneous cis-trans isomerisation and oxidative degradation accompanied by formation of a small amount (∼2 wt. %) of 1,3,5-triphenylbenzene. The extent of 1,3,5-triphenylbenzene formation was at least one order of magnitude lower than the extent of formation of new (shorter) PPhA macromolecules via their scission from the longer ones. Preparative MW-based fractionation revealed that a partly aged PPhA contains both (i) deeply isomerised macromolecules (forming the lower-MW fraction) and (ii) microstructurally unperturbed high-cis macromolecules (forming the higher-MW fraction). A hypothesis is postulated explaining the non-uniform distribution of high-cis and deeply isomerised trans-rich macromolecules along the MW distribution of partly aged PPhA. The hypothesis particularly assumes the acceleration of degradation of PPhA chains by simultaneous cis-trans isomerisation due to which the unpaired electron content is enhanced on the isomerised chains.     

Phosphatidylcholine-based nonaqueous photorheological fluids: effect of geometry and solvent

We report a detail study on photoinduced rheological changes in nonaqueous photorheological (PR) fluids obtained with 1,2-diacyl-sn-glycero-3-phosphocholine-based reverse wormlike micelles, 1-palmitoyl-2-oleophosphatidylcholine (POPC)/cyclohexane/H₂O, POPC/isooctane/H₂O, and L-α-dioleophosphatidylcholine (DOPC)/isooctane/H₂O systems. Initially, the mixtures form highly viscoelastic fluids of long, reverse wormlike micelles as confirmed by the rheological measurements. When photosensitive molecule, trans-CA, is added to these mixtures, they exhibit photosensitivity, and the viscoelasticity increases that decreases on UV irradiation. The nature of the substituent on the benzene ring of trans-CA influences the rheology. When hydroxycinnamic acid (HCA) (hydrophilic, ?OH group attached to the benzene ring of CA) is added to DOPC/isooctane/H₂O phase, separation occurs; while with the methoxycinnamic acid (MOCA) and methylcinnamic acid (MCA) (hydrophobic groups, ?OCH₃, and –CH₃ attached to the benzene ring of CA respectively) led to higher viscoelasticity. The study on the effects of position of the substitution on CA reveals the viscosity enhancement is in the order of p-?>?m-?>?o-isomers. The different geometries obtained because of substitution and photoinduced trans-cis isomerisation is responsible for the different rheology as confirmed by the dynamic rheology, the UV absorption, and the ¹H NMR spectrums. The ¹H NMR spectra revealed a change in the solubilization site of CA with irradiation. cis-CA (high solubility in water) is solubilized in the vicinity of water (at the hydrophilic end of DOPC) as compared with trans-CA. This disrupts the 3D networks of reverse wormlike micelles, decreasing the η ₀, plateau modulus, G _0, and relaxation time, τ _R of solution.     

Aromatization of aliphatic compounds—v : m-Dialkyl-benzenes and 2-benzyl-naphthalenes

Some cyclohexadienols, when heated at 220° with PyHCl, gave, through dehydration and isomerisation, the corresponding benzene derivatives. So 2,6-dibenzyliden-cyclohexanols gave m-dibenzyl-benzenes, 2-benzyliden-1-tetralols gave 2-benzyl-naphthalenes and 2,6-dicyclohexenyl cyclohexanols gave m-dicyclohexyl-benzenes. The correlation between these aromatisations and those of cyclohexenone acetic acids to arylacetic acids are here discussed. Some by-products, which were obtained in the aromatisation of 2-benzylidene-1-tetralols, are also described.