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Selective reduction strategies based on abundant-metal catalysts are very important in the production of chemicals. In this paper, a method for the electrochemical semihydrogenation and semideuteration of alkynes to form Z-alkenes was developed, using a simple nickel foam as catalyst and H3O+ or D3O+ as sources of hydrogen or deuterium. Good yields and excellent stereoselectivities (Z/E up to 20 : 1) were obtained under very mild reaction conditions. The reaction proceeded with terminal and nonterminal alkynes, and also with alkynes containing easily reducible functional groups, such as carbonyl groups, as well as aryl chlorides, bromides, and even iodides. The nickel-foam electrocatalyst could be recycled up to 14 times without any change in its catalytic properties.

Readily accessible tetraorganoborate salts undergo selective coupling reactions under blue light irradiation in the presence of catalytic amounts of transition-metal-free acridinium photocatalysts to furnish unsymmetrical biaryls, heterobiaryls and arylated olefins. This represents an interesting conceptual approach to forge C?C bonds between aryl, heteroaryl and alkenyl groups under smooth photochemical conditions. Computational studies were conducted to investigate the mechanism of the transformation.

Photocatalyst-free visible-light-mediated reactions, based on the presence of a visible-light-absorbing functional group in the starting material itself in order to exclude the often costly, hazardous, degradable and difficult to remove or recover photoredox catalysts, have been gaining momentum recently. We have employed this approach to develop a denitrative photocatalyst-free visible-light-mediated protocol for the arylation/sulfonylation of β-nitrostyrenes employing arylazo sulfones (bench-stable photolabile compounds) in a switchable solvent-controlled manner. Arylazo sulfones served as the aryl and sulfonyl radical precursors under blue LED irradiation for the synthesis oftrans-stilbenes and (E)-vinyl sulfones in CH3CN and dioxane/H2O 2?:?1, respectively. The absence of any metal, photocatalyst and additive; excellent selectivity (E-stereochemistry) and solvent-switchability; and the use of visible light and ambient temperature are the prime assets of the developed method. Moreover, we report the first photocatalyst-free visible light-driven route to synthesize stilbenes and vinyl sulfones from readily available β-nitrostyrenes.

The development of new catalytic processes based on abundantly available starting materials by cheap metals is always a fascinating task and marks an important transition in the chemical industry. Herein, a nickel-catalyzed acceptorless dehydrogenative coupling of alcohols with nitriles followed by decyanation of nitriles to access diversely substituted olefins is reported. This unprecedented C=C bond-forming methodology takes place in a tandem manner with the formation of formamide as a sole byproduct. The significant advantages of this strategy are the low-cost nickel catalyst, good functional group compatibility (ether, thioether, halo, cyano, ester, amino, N/O/S heterocycles; 43 examples), synthetic convenience, and high reaction selectivity and efficiency.

The Matsuda-Heck reaction, usually performed with palladium catalysts, can be carried out under transition-metal-free conditions in the presence of a KOtBu/DMF couple. This system allows the selective and direct synthesis of stilbenes from aryldiazonium salts under mild temperature (20 °C). Mechanistic studies suggest a radical pathway in which the DMF acts as the initiator of the overall process.

Heterogeneous chemoselective or stereoselective C-C coupling reactions remain extremely challenging in traditional organic synthesis. Here, we constructed a AuPd@N-rich carbon nitride (NRCN) photocatalyst through simple ammonia solution heat treatment of carbon nitride and then AuPd NP loading. AuPd@NRCN exhibited extraordinary light color promoted catalytic performance in C-C bond formation under visible light in air. Surprisingly, both high chemoselectivity to unsymmetrical Ullmann biaryl products and satisfactory stereoselectivity to Z-type Heck reaction products could be achieved by changing the light source color. Various substrates exhibited great potential for the economical synthesis of unsymmetrical biaryl products and Z-type olefins. Efficient visible light promoted C-I bond activation accompanied with improved photocatalytic coupling reaction efficiency over AuPd@NRCN was verified firstly by in situ DRIFTS. Considering that the Ullmann cross-coupling reaction is a multi-photon reaction, the improved photocatalytic performance in the Ullmann cross-coupling reaction using a combination of light sources with different colors might be due to the activation of different substrates and/or steps requiring different energies, and the combination of the two energy sources was beneficial for improving the activation efficiency of different substrates and/or steps. The activation of iodobenzene and styrene in the Heck reaction with light was also beneficial to the formation of the stilbene product. The light color promoted chemoselectivity and stereoselectivity are expected to have profound impact on organic synthetic methodology improvement. This journal is

Four Ru(II)-NC complexes were tested as catalysts for semihydrogenation of internal alkynes to (E)-alkenes with ethanol, and the complex {(C5H4N)(C6H4)}RuCl(CO)(PPh3)2 (1a) showed the highest activity. The reactions proceeded well with 1 mol % catalyst loading and 0.1 equiv of t-BuONa at 110 °C for 1 h, and 32 alkenes were synthesized with excellent E:Z selectivity. This is the first ruthenium-catalyzed semihydrogenation of internal alkynes to (E)-alkenes using ethanol as the hydrogen donor.

Herein, the first example of visible-light-driven, cobalt-catalyzed transfer semihydrogenation of alkynes to alkenes is reported. It is carried out by using Ir[dF(CF3)ppy]2(dtbbpy)]PF6 as photosensitizer, CoBr2/n-Bu3P as proton-reducing catalyst, and i-Pr2NEt/AcOH as the hydrogen source. Under the established catalytic system, the semihydrogenation proceeds with Z as the major selectivity and with inhibition of over-reduction. Under mild reaction conditions, both internal and terminal alkynes, as well as reducible functional groups such as halogen, cyano, and ester, are tolerated. Preliminary mechanistic studies revealed the dual role of the photosensitizer in initiating the reaction via a single-electron transfer process and controlling the stereoselectivity via an energy transfer process. (Figure presented.).

The carbon–carbon cross coupling reactions through transition-metal-catalyzed processes has been significantly developed for their important synthetic applications. In this research, we have shown that NiFe2O4@TASDA-Pd(0) is a highly active, novel and reusable catalyst with excellent performance for the Mizoroki–Heck coupling reaction of several types of iodo, bromo, and even aryl chlorides in DMF under ultrasound irradiation. The novel palladium catalyst prepared and characterized by using FT-IR spectrum, X-ray diffraction (XRD), scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), thermo gravimetric analysis (TGA) and vibrating sample magnetometer (VSM). The catalyst can be recovered and recycled several times without marked loss of activity.

The potential safety hazards associated with the Mizoroki-Heck cross-coupling of bromobenzenes with styrenes were evaluated. The heat output from the reaction in various solvents was comparable in a variety of solvents; however, the rate of reaction was significantly faster in the presence of water. Thermal stability evaluation of the postreaction mixtures in DMSO and 3:1 DMSO/water by differential scanning calorimetry indicated that the onset temperatures of thermal decomposition were significantly lower than that of neat DMSO. Evaluation of the substrate scope revealed that the substitution pattern on the bromobenzene did not affect the heat output. The reaction rate of electron-deficient bromobenzenes was slower than that of the electron-rich bromobenzenes. In general, substituted styrenes afforded similar magnitudes of exotherms; however, the reaction rate of bromobenzene with 2-methylstyrene was significantly slower than the other studied styrenes. The predicted heat of reaction using the density functional theory method, B3LYP, was in good agreement with the experimental data. Such excellent agreement suggests that this calculation method can be used as a preliminary tool to predict heat of reaction and avoid exothermic reaction conditions. In many of the studied cases, the maximum temperature of a synthesis reaction was considerably higher than the solvent boiling point and thermal decomposition onset temperatures when the reaction was performed in DMSO or 3:1 DMSO/water. It is crucial to understand the thermal stability of the reaction mixture to design the process accordingly and ensure the reaction temperature is maintained below the onset temperature of decomposition to avoid potential runaway reactions.

The invention discloses a method of photo-induced catalytic selective synthesis of Z- and E-olefins. According to the method, a disubstituted acetylene compound is used as a starting raw material, a cheap acid is used as a hydrogen source, a phosphine is

The invention discloses a photo-induced catalytic method for selectively synthesizing a cis olefin and a trans olefin by using alcohol as a hydrogen source. According to the method, a di-substituted acetylene compound is used as an initial raw material, t

The invention discloses a method for catalytic-selectively synthesizing Z- and E-alkene through alcohol supply hydrogen iridium controlled by a ligand. The method comprises the following steps: usinga disubstituted acetylene compound as a starting raw mat

A ligand-controlled iridium-catalyzed semihydrogenation of alkynes to E- and Z-alkenes with ethanol was developed. Effective selectivity control was achieved by ligand regulation. The use of 1,2-bis(diphenylphosphino)ethane (DPPE) and 1,5-cyclooctadiene (COD) was critical for the stereoselective semihydrogenation of alkynes. The general applicability of this procedure was highlighted by the synthesis of more than 40 alkenes, with good stereoselectivities. The value of our approach in practical applications was investigated by studying the effects of pinosylvin and 4,4′-dihydroxystilbene (DHS) on zebrafish as a vertebrate model.

Immobilized triazine bis[mercapto amine] complexes of Pd(0) (NiFe2O4@TABMA-Pd(0)) was easily synthesized and applied as highly efficient and versatile nanocatalyst for the synthesis of various trans stilbenes with high performance fo

A novel ligand-free palladium/copper-catalyzed Heck-type coupling reaction of alkenes and N′-acyl arylhydrazines has been developed by using air as the terminal oxidant. This protocol features wide functional group tolerance and produces highly chemoselective and regioselective products with good to excellent yields.

A simple, novel and stereoselective synthesis of trans-stilbenes has been described using denitrative arylation of β-nitrostyrenes in the presence of benzoyl peroxide under metal-free conditions. The reaction is assumed to involve homolytic cleavage of benzoyl peroxide followed by decarboxylation to generate a phenyl radical, which brings about ipso-substitution of the nitro group of nitrostyrenes to afford trans-stilbenes.

Reactions of [NH4]2[PdCl4] with N-protonated or N-alkyl-1,3,5-triaza-7-phosphaadamantane iodide salts [PTA-R]I (R = H, Me, Et, nPr, nBu) give the water-soluble palladium(II) complexes of type [PdI3(PTA-R)] in isolated yields of 62–81%. All these compounds have been fully characterized by IR and NMR spectroscopies and elemental analyses. Their molecular structures were confirmed by single crystal X-ray diffraction analysis. The complexes belong to the relatively unusual zwitterionic, coordination compounds. Moreover, they constitute, as far as we are aware, the first reported examples of palladium compounds bearing N-alkyl-1,3,5-triaza-7-phosphaadamantane ligands. The complexes catalyze efficiently Heck reaction of iodobenzene and n-butyl acrylate as well as iodobenzene and substituted styrenes, under mild conditions in water as a solvent.

The straightforward visible-light-induced synthesis of stilbene compounds via the cross-coupling of nitroalkenes and diazonium tetrafluoroborates under transition-metal-free conditions is described. The protocol uses green LEDs as light sources and eosin Y as an organophotoredox catalyst. Broad substrate scope and exclusive selectivity for the (E)-configuration of stilbenes are observed. This protocol proceeds via a radical pathway, with nitroalkenes serving as the radical acceptor, and the nitro group is cleaved during the process.

The first catalytic dehydrative condensation of the benzylic C-H bonds of toluene and p-xylene with aromatic aldehydes is reported herein. This protocol provides highly atom-economical access to stilbene and p-distyrylbenzene derivatives, whereby water is the sole byproduct. The reaction is based on the deprotonation-functionalization of benzylic C-H bonds through η6-complexation of the arenes, which is realized for the first time using a catalytic amount of a transition metal activator. The key to the success of this method is the use of a sulfonamide anion as a catalyst component, which appears to facilitate not only the deprotonation of the benzylic C-H bonds but also the formation of a C-C bonds via an electrophilic tosylimine intermediate.

Herein, we report a novel cobalt-catalyzed stereodivergent transfer hydrogenation of alkynes to Z- and E-alkenes. Effective selectivity control is achieved based on a rational catalyst design. Moreover, this mild system allows for the transfer hydrogenation of alkynes bearing a wide range of functional groups in good yields using catalyst loadings as low as 0.2 mol %. The general applicability of this procedure is highlighted by the synthesis of more than 50 alkenes with good chemo- and stereoselectivity. A preliminary mechanistic study revealed that E-alkene product was generated via sequential alkyne hydrogenation to give Z-alkene intermediate, followed by a Z to E alkene isomerization process.

The preparation of palladium nanoparticles supported on acetylacetone-modified silica gel and their catalytic application for Heck olefination of aryl halides were investigated. The catalyst was characterized using X-ray diffraction, X-ray photoelectron spectroscopy, and transmission and scanning electron microscopies. The supported palladium nanoparticles are demonstrated to be a highly active and reusable catalyst for the Heck reaction. Several reaction parameters, including type and amount of solvent and base, were evaluated. The heterogeneity of the catalytic system was investigated with results indicating that there is a slight palladium leaching into the reaction solution under the applied reaction conditions. Despite this metal leaching, the catalyst can be reused nine times without significant loss of catalytic activity.

The present invention relates to method(s) of treating a subject afflicted with a skin disease or condition, the method comprising administering to the subject or patient in need a composition comprising a therapeutically effective amount of a substituted cis or trans- stilbene or a stilbene hybrid. A method of treating or reducing the likelihood of a skin disease or condition in a patient is an additional embodiment of the present invention. Preferred pharmaceutical compositions of the invention include nanoemulsions comprising a therapeutically effective amount of a substituted cis or trans-stilbene or stilbene hybrid and at least one antibiotic.

A rhodium-catalyzed oxidative decarbonylative Heck-type coupling of aromatic aldehydes with terminal alkenes to afford 1,2-disubstituted alkenes with good regio- and E-selectivity is developed. This reaction employs readily available aromatic aldehydes as the aryl electrophile counterpart and relies on selected acyl chloride as the crucial additive to activate the rhodium catalyst precursor.

Mesoporous poly(N-vinyl-2-pyrrolidone) (MPVP) was prepared through a nanocasting technique based on mesoporous silica KIT-6 as sacrificial templates, and served as an efficient scaffold for supporting Pd nanoparticles. The physical and chemical properties

The pair NaBH4-TMEDA and catalytic PdCl2(PPh 3)2 in THF at room temperature is a mild and efficient system for the hydrodebromination of alkenyl bromides, providing a facile reduction procedure that allows completing the process advantageously, leading from aldehydes to (E)-alkenes. This journal is the Partner Organisations 2014.

An unprecedented oxidative arylation reaction of terminal alkenes with simple aroyl hydrazides has been developed under aerobic conditions for the stereoselective synthesis of 1,2-disubstituted alkenes. A range of aroyl hydrazides underwent palladium/copper-catalyzed oxidative Mizoroki-Heck reaction with terminal alkenes open to air in a 1:1 mixture of dimethyl sulfoxide and acetonitrile to give structurally diverse 1,2-disubstituted alkenes in moderate to excellent yields with excellent regio- and E-selectivity. The reaction tolerated a wide variety of functional groups, such as alkoxy, hydroxy, amino, fluoro, chloro, bromo, cyano, nitro, ester, amide, imide, phosphine oxide, and sulfone groups, and, moreover, molecular oxygen and dimethyl sulfoxide were demonstrated to serve as terminal oxidants. This study provides a useful method for the stereoselective synthesis of 1,2-disubstituted alkenes through direct transformation of the vinylic Ci-H bonds in terminal alkenes. Cross-coupling: An oxidative arylation reaction of terminal alkenes with simple aroyl hydrazides has been developed in the presence of a PdCl2/CuI catalyst under aerobic conditions to give a range of structurally diverse 1,2-disubstituted alkenes in moderate to excellent yields with excellent regio- and E-selectivity (see scheme; r.s.=regioselectivity).

Dichloro-bis(aminophosphine) complexes of palladium with the general formula [(P{(NC5H10)3-n(C6H 11)n})2Pd(Cl)2] (where n = 0-2) are easily accessible, cheap and air stable, highly active and universally applicable C-C cross-coupling catalysts, which exhibit an excellent functional group tolerance. The ligand composition of amine-substituted phosphines (controlled by the number of P-N bonds) was found to effectively determine their catalytic activity in the Heck reaction, for which nanoparticles were demonstrated to be their catalytically active form. While dichloro{bis[1, 1′,1′′-(phosphinetriyl)tripiperidine]}palladium (1), the least stable complex (towards protons) within the series of [(P{(NC5H 10)3-n(C6H11)n}) 2Pd(Cl)2] (where n = 0-3), is a highly active Heck catalyst at 100 °C and, hence, a rare example of an effective and versatile Heck catalyst that efficiently operates under mild reaction conditions (100 °C or below), a significant successive drop in activity was noticed for dichloro-bis(1,1′-(cyclohexylphosphinediyl)dipiperidine)palladium (2, with n = 1), dichloro-bis(1-(dicyclohexylphosphinyl)piperidine)palladium (3, with n = 2) and dichloro-bis(tricyclohexylphosphine)palladium (4, with n = 3), of which the latter is essentially inactive (at least under the reaction conditions applied). This trend was explained by the successively increasing complex stability and its ensuing retarding effect on the (water-induced) generation of palladium nanoparticles thereof. This interpretation was experimentally confirmed (initial reductions of 1-4 into palladium(0) complexes of the type [Pd(P{(NC5H10)3-n(C6H 11)n})2] (where n = 0-3) were excluded to be the reason for the activity difference observed as well as molecular (Pd 0/PdII) mechanisms were excluded to be operative) and thus demonstrates that the catalytic activity of dichloro-bis(aminophosphine) complexes of palladium can-in reactions where nanoparticles are involved-effectively be controlled by the number of P-N bonds in the ligand system.

Pd(II) anionic, square planar complexes of the type [RPPhPdl, where X = Cl, Br, have been applied for the first time as a catalyst precursor for the Heck reaction carried out in DMF at 140 °C. The highest yield was obtained for the most reducible ones, [MePPhPdrl, in DMF in the presence of NaHCOas a base. It was found that during the reaction, phosphonium halide stabilized Pd(0) nanoparticles of about 10 nm, which have been formed in situ from the palladium(II) precursor and Pd(0) colloidal nanoparticles acts as the reservoir for Pd(II) species via activation of the metal surface through the oxidative addition of aryl halides. Georg Thieme Verlag Stuttgart New York.

A novel ligand-free indium(III)-catalyzed Heck reaction of various aryl iodides with olefins has been developed. As a result, a set of the corresponding E-internal olefins was obtained selectively in high to excellent yields. The reaction condition is tolerant to air, in accordance with the concept of modern green chemistry.

Pd nanoparticles generated in green reaction media (viz. ionic liquids and water) catalyze the one-pot sequential Heck and Suzuki coupling reactions of bromo-chloroarenes to afford unsymmetrically substituted arenes in good yields.

The activity of {Pd[C6H2(CH2CH 2NH2)-(OMe)2,3,4] (μ-Br)}2 complex was investigated in the Heck-Mizoroki C-C cross-coupling reaction under conventional heating and microwave irradiation conditions in molten salt tetrabutylammonium bromide as the solvent and promoter at 130 °C. This complex in these conditions is an active and efficient catalyst for the Heck reaction of aryl iodides, bromides and even chlorides, and also arenesulfonyl chlorides. Copyright

The [Pd{C6H2(CH2CH2NH 2)-(OMe)2,3,4}Br(PPh3)] monomeric orthopalladate complex of homoveratrylamine and triphenylphosphine was synthesized and its application in Heck coupling reactions was investigated. This complex had been demonstrated to be more active than the corresponding dimeric catalyst for Heck reactions of aryl iodides, bromides and even chlorides and also arenesulfonyl chlorides. The cross-coupled products were produced in excellent yields using catalytic amounts of [Pd{C6H 2(CH2CH2NH2)-(OMe) 2,3,4}Br(PPh3)] as a thermally stable and oxygen insensitive complex in NMP at 130 °C.

Non-cross-linked polystyrene-supported (carbomethoxymethyl) triphenylarsonium bromide (1) and benzyltriphenylarsonium iodide (2) were synthesized. They showed similar reactivities compared with the free arsonium salts in the arsa-Wittig reaction. The use of the polymer-supported reagents facilitated product purification and rendered the organoarsenic reagents easily separable and recyclable.

The activity of [Pd(C6H4CH2 NH 2-κ2-C-N)PPh3MOBPPY]OTf complex, A (MOBPPY = 4-methoxybenzoylmethylenetriphenyl- phosphoraneylide), was investigated in the Heck-Mizoroki C-C cross-coupling reaction under conventional heating and microwave irradiation conditions. The complex is an active and efficient catalyst for the Heck reaction of aryl halides. The yields were excellent using a catalytic amount of [Pd(C6H4CH 2 NH2-κ2-C-N)PPh3MOBPPY]OTf complex in N-methyl-2-pyrrolidinone (NMP) at 130 °C and 600 W. In comparison to conventional heating conditions, the reactions under microwave irradiation gave higher yields in shorter reaction times. Copyright

The Wittig reaction involving direct olefination of triphenylphosphonium ylides (Ph3PCHR) with aldehydes is arguably the most often used method for alkene synthesis, but in general it yields mixtures of Z- and E-alkenes for semistabilized triphenylphosphonium ylides (R = aryl or vinyl). We have developed a simple and efficient protocol to improve the stereoselectivity significantly by replacing the aldehydes used in the Wittig reaction with N-sulfonyl imines, which possess distinct electronic and steric properties relative to aldehydes. A broad range of aromatic, α,β-unsaturated, and aliphatic imines bearing appropriate N-sulfonyl groups smoothly undergo olefination reaction with various benzylidenetriphenylphosphoranes or allylidenetriphenylphosphoranes under mild reaction conditions to afford an array of both Z- and E-isomers of conjugated alkenes in good to excellent yields and with greater than 99:1 stereoselectivity. Moreover, this tunable protocol has been successfully applied to the highly stereoselective synthesis of two anticancer agents, DMU-212 and its Z-isomer.

A mild and efficient method for oxidative Heck-type reaction of arylboronic acids with olefins catalyzed by cyclopalladated ferrocenylimine was developed. The results represent the first examples involving the palladacycle as the catalyst for such couplings. Moreover, the catalytic system could tolerate various functional groups, such as F, Cl, Br, NO2 and CH3O, and the substrates could be extended to a wide range of olefins from acrylic esters, α,β-unsaturated ketones to alkenes. Furthermore, the olefination could proceed well under base- and ligand-free conditions and employ oxygen as the environmentally benign oxidant.

The [Pd{C6H2(CH2CH2NH2)-(OMe)2,3,4} (μ-Br)]2 complex of homoveratrylamine was synthesized and its application in the Heck coupling reaction was studied. This complex had been demonstrated to be active and efficient catalyst for the Heck reaction of aryl iodides, bromides and even chlorides. The cross-coupled products were produced in excellent yields in a short reaction time using catalytic amounts of [Pd{C6H2(CH2CH2NH2)-(OMe)2,3,4} (μ-Br)]2 complex in N-methyl-2-pyrrolidinone (NMP at 130 °C).

The present invention relates to method(s) of treating a subject afflicted with cancer or a precancerous condition, an inflammatory disease or condition, and/or stroke or other ischemic disease or condition, the method comprising administering to the subject or patient in need a composition comprising a therapeutically effective amount of a substituted cis or trans-stilbene.

In the presence of a catalytic amount of PdCl2(PPh 3)2 and a silylating agent, organozinc halides reacted with carbonyl compounds to give the corresponding (E)-stilbenes in good to excellent yields under mild conditions. The reaction mechanism is briefly discussed.

The transcription factor nuclear factor kappaB (NF-κB), which regulates expression of numerous antiinflammatory genes as well as genes that promote development of the prosurvival, antiapoptotic state is up-regulated in many cancer cells. The natural product resveratrol, a polyphenolic trans-stilbene, has numerous biological activities and is a known inhibitor of activation of NF-κB, which may account for some of its biological activities. Resveratrol exhibits activity against a wide variety of cancer cells and has demonstrated activity as a cancer chemopreventive against all stages, i.e., initiation, promotion, and progression. The biological activities of resveratrol are often ascribed to its antioxidant activity. Both antioxidant activity and biological activities of analogues of resveratrol depend upon the number and location of the hydroxy groups. In the present study, phenolic analogues of resveratrol and a series of substituted trans-stilbenes without hydroxy groups were compared with resveratrol for their abilities to inhibit the human tumor necrosis factor alpha-induced (TNF-α) activation of NF-κB, using the Panomics NF-κB stable reporter cell line 293/NF-κB-luc. A series of 75 compounds was screened to identify substituted trans-stilbenes that were more active than resveratrol. Dose-response studies of the most active compounds were carried out to obtain IC50 values. Numerous compounds were identified that were more active than resveratrol, including compounds that were devoid of hydroxy groups and were 100-fold more potent than resveratrol. The substituted trans-stilbenes that were potent inhibitors of the activation of NFκB generally did not exhibit antioxidant activity. The results from screening were confirmed using BV-2 microglial cells where resveratrol and analogues were shown to inhibit LPS-induced COX-2 expression.

Stereoselective alkenylated compounds are formed from the reaction of organozinc halides and aldehydes (see scheme; FG = functional group). Under mild conditions, and in the presence of a silylating agent, the Ni-catalyzed procedure gives E-alkenes and E-

Aromatic aldehydes react with ketones to produce (E)-1-aryl-1-alkenesvia a tandem Aldol-Grob cleavage reaction sequence. The reaction, initiated by boron trifluoride, also produces a carboxylic acid fragment.

Styrene reacts with arenediazonium chlorides in the presence of FeCl2 as catalyst to give 1-chloro-1-phenyl-2-arylethanes along with minor amounts of 1,4-diaryl-2,3-diphenylbutanes. Ferrous chloride turned out to be a more active catalyst in the chloroarylation of styrene than copper chlorides.

A combination of zinc metal and a catalytic amount of chlorotrimethylsilane has been found to promote the transformation of various aldehydes and ketones with gem-dichloro compounds, such as benzylidene dichloride (1a) and methyl dichloroacetate (1b), to the corresponding cross- coupling products, such as substituted styrene 3 and methyl acrylates 4 derivatives, under mild reaction conditions in THF. The E-isomer of the corresponding alkenes was obtained stereoselectively in good-to-excellent yields. The reaction serves as a very convenient one-pot procedure.

Main route of the reaction between m-phenylenebisdiazonium tetrafluoroborate with unsaturated compounds (acrylonitrile, styrene, alkyl acrylates and methacrylates) in the presence of NaCl and a catalyst (CuCl2) is the Meerwein chloroarylation by one diazogroup; the second diazogroup is replaced by chlorine according to Sandmayer's reaction.

Mechanistic studies of the cyclopropanation of a series of trans-stilbenes by ethyl diazoacetate catalyzed by two different triarylaminium salts decisively confirm a cation radical mechanism and rule out a hypothetical electrophilic mechanism. The elucidation of key aspects of these cation radical mechanisms, including kinetic vs equilibrium control of ionization and chain vs catalytic mechanisms, has also been achieved for these systems. New mechanistic criteria for the positive identification of cation radical mechanisms are proposed.

A kinetic study of the hydrolysis of substituted α-nitrostilbenes (NS-Z with Z = 4-Me, H, 4-Br, 3-NO2, and 4-NO2) in 50% Me2SO-50% water (v/v) at 20 °C is reported. The mechanism consists of four steps: nucleophilic addition to NS-Z of water (k1H2O) and OH- (k1OH) to form PhCH(OH)C(Ar)NO2- (TOH-); carbon protonation of TOH- by water (k2H2O), H3O+ (k2H), and buffer acids (k2BH) to form PhCH(OH)CH(Ar)NO2 (TOH0); rapid oxygen deprotonation of TOH0 (KaOH) to form PhCH(O-)CH(Ar)NO2 (TO-); collapse of TO- (k4) into benzaldehyde and arylnitromethane anion. The aci-form of TOH0, PhCH(OH)CH(Ar)NO2H (TOH,aci0), can also be generated as a transient by reaction of TOH- with strong acid. A combination of kinetic experiments involving the reaction of the olefin with water and OH-, the reaction of TOH- with acid, and the reaction of independently synthesized TOH0 with base allowed the dissection of the rate coefficients of most of the individual steps. From the substituent dependence of these rate coefficients, it is concluded that water and OH- addition to NS-Z (k1H2O and k1OH) as well as the collapse of TO- to benzaldehyde and ArCH=NO2- (k4) is characterized by substantial transition-state imbalances, reminiscent of the imbalance observed in the deprotonation of ArCH2NO2. It is also shown that the intrinsic rate constants for the k1OH and k4 steps are low compared to those for the corresponding steps in the hydrolysis of other olefins of the type PhCH=CXY (XY = (H, NO2), (CO)2C6H4, (COO)2C(CHj)2, and (CN)2). This again parallels the behavior in the deprotonation of ArCH2NO2.

A series of rhenium(0) radicals were spin trapped by 9,10-phenanthroquinone (C14H8O2) and its derivatives, , , and (n=1, X=H, OMe-3, Cl-3, Br-3, Pri-3, CN-3

(1RS,2SR)-1,2-Diphenyl-2-diphenylphosphonoylethanol (erythro-isomer) (1) and its threo-isomer (2) have been prepared stereospecifically by opening the appropriate stilbene oxides with Ph2PLi followed by oxidation with H2O2-AcOH.Compounds (1) and (2) can also be obtained stereoselectively (erythro-isomer predominating) via treatment of Ph2POCHLiPh with PhCHO.Under all the conditions tried, treatment of the threo-isomer (2) with base gave (E)-stilbene.The erythro-isomer (1) under most conditions gave predominantly (E)-stilbene, together with variable amounts of Ph2POCH2Ph, through in one case mainly (Z)-stilbene was formed.The conversion erythro-(E)-stilbene was shown to occur via fragmentation to Ph2POCHLiPh and PhCHO by trapping experiments using m-chlorobenzaldehyde.