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Polyalphaolefins (PAOs) have potential applications as synthetic lubricants in automotive, industrial, and aviation equipment, including motor oils, hydraulic, and transmission fluids. During the present work, the linear higher alpha olefins (LHAOs) ranging from [C.sub.8] to [C.sub.12] present in the refinery stream (RS) are polymerized using Lewis acid catalyst combination of transition metal halide of Group 4, that is, Ti[Cl.sub.4] and Group 13 metal halide, that is, Al[Cl.sub.3]. The influence of Ti:Al (1:1, 1.5:1, 1:2, and 2:1) molar ratios, polymerization time (2-8 h), and polymerization temperature (100-170[degrees]C) on the polymerization behavior of LHAOs were also investigated. The synthesized PAOs were characterized using different analytical techniques, including [sup.1]H-[sup.13]C nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and gel permeation chromatography (GPC). The performance evaluation of PAOs was evaluated in terms of density, pour point, oxidation stability, thermal stability, kinematic viscosity (KV), viscosity index (VI), friction, and corrosion studies. The synthesized PAOs exhibit low pour point ( KEYWORDS cationic polymerization, linear higher alpha olefins, polyalphaolefins, synthetic lubricants, 1 | INTRODUCTION Polyalphaolefins (PAOs) are saturated hydrocarbons widely used in the production of high-performance synthetic lubricants. They are mainly synthesized from linear higher alpha olefins (LHAOs) ranging from [C.sub.8] [...]

Abstract Copolymers of propylene/1-octene and propylene/1-hexene were synthesized in slurry phase polymerization using Mg[Cl.sub.2]/Ti[Cl.sub.4]/Diester based catalyst system. The Al/Do (co-catalyst/external donor), Al/Ti (co-catalyst/catalyst) mole ratio variations were investigated for effect [...]

Author(s): Ala Bunescu [sup.1] , Yusra Abdelhamid [sup.1] , Matthew J. Gaunt [sup.1] Author Affiliations: (1) Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK Main The reactivity of [...], Molecules that contain the [beta]-arylethylamine motif have applications in the modulation of pain, treatment of neurological disorders and management of opioid addiction, among others, making it a privileged scaffold in drug discovery.sup.1,2. De novo methods for their assembly are reliant on transformations that convert a small class of feedstocks into the target compounds via time-consuming multistep syntheses.sup.3-5. Synthetic invention can drive the investigation of the chemical space around this scaffold to further expand its capabilities in biology.sup.6-9. Here we report the development of a dual catalysis platform that enables a multicomponent coupling of alkenes, aryl electrophiles and a simple nitrogen nucleophile, providing single-step access to synthetically versatile and functionally diverse [beta]-arylethylamines. Driven by visible light, two discrete copper catalysts orchestrate aryl-radical formation and azido-group transfer, which underpin an alkene azidoarylation process. The process shows broad scope in alkene and aryl components and an azide anion performs a multifaceted role both as a nitrogen source and in mediating the redox-neutral dual catalysis via inner-sphere electron transfer.sup.10,11. The synthetic capabilities of this anion-mediated alkene functionalization process are likely to be of use in a variety of pharmaceutically relevant and wider synthetic applications. A streamlined synthesis of [beta]-arylethylamines using two distinct copper catalysts is reported, and an azide anion is proposed to both react to form the product and facilitate catalyst regeneration.

The reactivity of an electron-rich Ni-difluorocarbene complex, Ni=[CF.sub.2][(dppe)[P(OMe).sub.3]] (1), with a variety of fluorinated alkenes was investigated (dppe = 1,2-bis(diphenylphosphino)ethane). Reactions of 1 with perfluoro(methyl vinyl ether) and chlorotrifluoroethylene (CTFE) give regiospecific formation of metallacyclobutanes, in which the carbene C attacks the most electron-rich carbon of the fluoroalkene. Further reaction of the CTFE-derived metallacycle in the presence of tetrahydrofuran affords a single isomer of NiCl(r-[CF.sub.2]CF=CFH) (dppe), 8, proposed to be formed by Ni-mediated [C.sub.a]-Cl activation followed by hydride abstraction and loss of HF. Although 1 also undergoes a cyclization reaction with trifluoroethylene (TrFE), instability of the presumed nickelacyclobutane affords the C3 fluoroalkene, [F.sub.2]C=CH([CF.sub.3]), and subsequent formation of isomeric metallacyclopentanes from two additional TrFEs. Alternatively, reaction of 1 with hexafluoropropene forms an unexpected Ni--[CF.sub.3] r-perfluoroallyl complex. Key words: nickel difluorocarbene, fluoroalkene, cycloaddition, C--F bond activation. La reactivite d'un complexe de difluorocarbene-nickel riche en electrons, le Ni-[CF.sub.2](dppe)[P(OMe)] (1), avec une variete d'alcenes fluores a ete etudiee [dppe = 1,2-bis(diphenylphosphino)ethane]. Les reactions du complexe 1 avec le perfluoro(methylvinylether) et le chlorotrifluoroethylene (CTFE) donnent lieu a la formation regiospecifique de metallacyclobutanes, dans lesquels le C du carbene attaque le carbone le plus riche en electrons du fluoroalcene. La poursuite de la reaction du metallacycle derive du CTFE en presence de tetrahydrofurane produit un seul isomere de NiCl([sCF.sub.2]CF=CFH) (dppe), le complexe 8, dont la formation pourrait etre attribuable a l'activation de la liaison [C.sub.a]Cl catalysee par le Ni, suivie de l'abstraction de l'hydrure et de la perte d'une molecule de HF. Bien que le complexe 1 subisse egalement une reaction de cyclisation avec le trifluoroethylene (TrFE), l'instabilite du suppose nickelacyclobutane permettrait la formation du fluoroalcene en C3, le [F.sub.2]C=CH([CF.sub.3]), puis la formation subsequente de metallacyclopentanes isomeriques provenant de deux autres molecules de TrFE. Sinon, la reaction du complexe 1 avec l'hexafluoropropene forme un complexe inattendu de [CF.sub.3]sperfluoroallylNi. [Traduit par la Redaction] Mots-cles : difluorocarbene-nickel, fluoroalcene, cycloaddition, activation de liaisons C--F., Introduction Reactions involving metal alkylidenes and carbenes are some of the most valuable and desired catalytic transformations. (1-4) Although the reactivity of metal carbenes has been thoroughly studied and established, [...]

Diene self-exchange reactions of the 17-electron, formally cobalt(0) cyclooctadienyl precatalyst, (R,R)-([.sup.iPr]DuPhos)Co(COD) ([P.sub.2]CoCOD, (R,R)-[.sup.iPr]DuPhos = 1,2-bis((2R,5R)-2,5-diisopropylphospholano)benzene, COD = 1,5-cyclooctadiene) were studied using natural abundance and deuterated 1,5-cyclooctadiene. Exchange of free and coordinated diene was observed at ambient temperature in benzene-[d.sub.6] solution and kinetic studies support a dissociative process. Both neutral [P.sub.2]CoCOD and the 16-electron, cationic cobalt[(I) complex, [[(R,R)-([.sup.iPr]DuPhos)Co(COD)][[BAr.sup.F.sub.4]] ([BAr.sup.F.sub.4] = B[(3,5-([CF.sub.3]).sub.2])[C.sub.6][H.sub.3]].sub.4]) underwent instantaneous displacement of the 1,5-cyclooctadiene ligand by carbon monoxide and generated the corresponding carbonyl derivatives. The solid-state parameters, DFT-computed Mulliken spin density and analysis of molecular orbitals suggest an alternative description of [P.sub.2]CoCOD as low-spin cobalt(II) with the 1,5-cyclooctadiene acting as a [LX.sub.2]-type ligand. This view of the electronic structure provides insight into the nature of the ligand substitution process and the remarkable stability of the neutral cobalt complexes toward protic solvents observed during catalytic alkene hydrogenation. Key words: cobalt, ligand substitution, metallacyclopropane, hydrogenation. Nous avons etudie les reactions d'auto-echange de diene dans le complexe a 17 electrons, formellement le pre-curseur du catalyseur cyclooctadienyl cobalt(0), le (R,R)([.sup.iPr]DuPhos)Co(COD) ([P.sub.2]CoCOD, (R,R)[.sup.iPr]DuPhos = 1,2bis((2R,5R)-2,5-diisopropylphospholano)benzene, COD = 1,5cyclooctadiene) a l'aide du 1,5cyclooctadiene d'abondance naturelle et deutere. L'echange de diene libre et coordonne a ete observe a temperature ambiante dans une solution de [benzened.sub.6], et les etudes cinetiques indiquent un processus dissociatif. Le complexe [P.sub.2]CoCOD neutre tout comme le complexe cationique de cobalt[(I) a 16 electrons [[[(R,R)([.sup.iPr]DuPhos)Co(COD)][[BAr.sup.F.sub.4]] ([BAr.sup.F.sub.4] = B[(3,5([CF.sub.3]).sub.2])[C.sub.6][H.sub.3]].sub.4]) ont subi un deplacement instantane du ligand 1,5cyclooctadiene par le monoxyde de carbone et ont forme les derives carbonyle correspondants. Les parametres de l'etat solide, la densite de spin de Mulliken calculee par la theorie de la fonctionnelle de la densite (DFT) et l'analyse des orbitales moleculaires evoquent une autre description du complexe [P.sub.2]CoCOD, ou l'atome de cobalt (II) presente un faible spin et le 1,5cyclooctadiene agit comme ligand de type [LX.sub.2]. Cette facon de voir la structure electronique met en lumiere la nature des processus de substitution de ligand et la stabilite remarquable des complexes neutres de cobalt a l'egard des solvants protiques que l'on observe au cours de l'hydrogenation catalytique de l'alcene. [Traduit par la Redaction] Mots-cles : cobalt, substitution de ligand, metallacyclopropane, hydrogenation., Introduction Catalysis with Earth-abundant, first-row transition metals has witnessed a renaissance of interest recently due to potential economic and environmental advantages, as well as reactivity distinct from more widely used [...]

Author(s): Yumeng Xi [sup.1] [sup.2] , Senjie Ma [sup.1] [sup.2] , John F. Hartwig [sup.1] [sup.2] Author Affiliations: (1) Department of Chemistry, University of California, Berkeley, USA (2) Division of [...], Hydroamination of alkenes, the addition of the N-H bond of an amine across an alkene, is a fundamental, yet challenging, organic transformation that creates an alkylamine from two abundant chemical feedstocks, alkenes and amines, with full atom economy.sup.1-3. The reaction is particularly important because amines, especially chiral amines, are prevalent substructures in a wide range of natural products and drugs. Although extensive efforts have been dedicated to developing catalysts for hydroamination, the vast majority of alkenes that undergo intermolecular hydroamination have been limited to conjugated, strained, or terminal alkenes.sup.2-4; only a few examples occur by the direct addition of the N-H bond of amines across unactivated internal alkenes.sup.5-7, including photocatalytic hydroamination.sup.8,9, and no asymmetric intermolecular additions to such alkenes are known. In fact, current examples of direct, enantioselective intermolecular hydroamination of any type of unactivated alkene lacking a directing group occur with only moderate enantioselectivity.sup.10-13. Here we report a cationic iridium system that catalyses intermolecular hydroamination of a range of unactivated, internal alkenes, including those in both acyclic and cyclic alkenes, to afford chiral amines with high enantioselectivity. The catalyst contains a phosphine ligand bearing trimethylsilyl-substituted aryl groups and a triflimide counteranion, and the reaction design includes 2-amino-6-methylpyridine as the amine to enhance the rates of multiple steps within the catalytic cycle while serving as an ammonia surrogate. These design principles point the way to the addition of N-H bonds of other reagents, as well as O-H and C-H bonds, across unactivated internal alkenes to streamline the synthesis of functional molecules from basic feedstocks. Hydroamination with high enantio- and regioselectivity is achieved across a wide range of internal alkenes by using a cationic iridium complex that adds an ammonia surrogate containing a pyridine group.

Abstract: Oligomeric phosphaalkenes are readily characterized using electrospray ionization mass spectrometry (ESI-MS). The high affinity of phosphines for silver ions permits the detection of the unadulterated polymer as [[M + [...]

Now that we have completed our discussion of benzene rings and the infamous 'benzene fingers,' the next topic on our hydrocarbon hit parade is carbon-carbon double bonds. C=C bonds, otherwise [...]

The olefin metathesis reaction of two unsaturated substrates is one of the most powerful carbon-carbon-bond-forming reactions in organic chemistry. Specifically, the catalytic olefin metathesis reaction has led to profound developments [...]

Alkenes are the most ubiquitous prochiral functional groups--those that can be converted from achiral to chiral in a single step--that are accessible to synthetic chemists. For this reason, difunctionalization reactions [...]

INTRODUCTION O-alkyl-N,N-Dialkylphosphorarriido cyanidates (OAPAC, I) are highly toxic compounds [1, 2] subjected to control under the Chemical Weapons Convention [3]. [FORMULA NOT REPRODUCIBLE IN ASCII] where, R, R', R' are [...], A method is proposed for the prediction of electron-ionization mass spectra of highly toxic O-alkyl-N,N-dialkylphosphoramido cyanidates. The approach is based on the fact that the compounds can be divided into three groups by the type of fragmentation. The main group (O-alkyl, O-methyl, O-ethyl) containing almost all compounds of this class (61440 of 61460), in its turn, can be divided into ten subgroups characterized by different combinations of two N-alkyl radicals. Each subgroup possesses its specific generalized spectral image, i.e., a set of peaks characterized by mass numbers and relative intensities. A spectrum of an individual O-alkyl-N,N-dialkylphosphoramido cyanidate is considered as a sum of the generalized spectral image of a corresponding subgroup and a spectrum of an alkene with a carbon chain identical to the O-alkyl group of the molecule. Keywords: O-alkyl-N,N-dialkylphosphoramido cyanidates, electron-ionization mass spectra, generalized mass-spectral image, prediction of mass spectra. DOI:10.1134/S1061934811130089

A cost-effective and efficient solid Br0nsted acid catalyst was synthesized by loading methanesulfonic acid (MSA) on silica and was used for the acid-catalyzed Pechmann reaction to test the catalytic activity and its reusability. Derivatives of 4-methylcoumarin were synthesized in good yields within short reaction times in the presence of environmentally friendly higher n-alkanes as solvents. The regeneration study of the spent catalyst showed satisfactory results. Key words: silica supported solid acids, methanesulfonic acid, Br0nsted acidity, Pechmann reaction, derivatives of 4-methylcoumarin. On a synthetise un catalyseur acide de Br0nsted efficace et rentable d'un point de vue cout en recouvrant de la silice avec de l'acide methanesulfonique (AMS) et on l'a utilise catalyseur acide pour la reaction de Pechmann dans le but d'evaluer son activite catalytique et la possibilite de le reutiliser. On a synthetise des derives de la 4-methylcoumarine avec de bons rendements, avec des temps de reaction relativement courts, dans des solvants a base d'alcanes superieurs ecologiques. L'etude de regeneration du catalyseur utilise a donne des resultats satisfaisants. Mots-cles : acides solides supportes par de la silice, acide methanesulfonique, acidite de Bronsted, reaction de Pechman, derives de la 4-methylcoumarine., Introduction Methanesulfonic acid (C[H.sub.3]S[O.sub.3]H; MSA) is a strong Br0nsted acid ([pK.sub.a] = -1.9) and has been reported as a potential acid catalyst for various acid-catalyzed reactions. (1-3) MSA is very [...]

In spite of the many catalytic methodologies available for the asymmetric functionalization of carbonyl compounds at their [alpha] and [beta] positions, little progress has been achieved in the enantioselective carbon--carbon bond formation y to a carbonyl group. Here, we show that primary amine catalysis provides an efficient way to address this synthetic issue, promoting vinylogous nucleophilicity upon selective activation of unmodified cyclic [alpha],[beta]-unsaturated ketones. Specifically, we document the development of the unprecedented direct and vinylogous Michael addition of [beta]-substituted cyclohexenone derivatives to nitroalkenes proceeding under dienamine catalysis. Besides enforcing high levels of diastereo- and enantioselectivity, chiral primary amine catalysts derived from natural cinchona alkaloids ensure complete [gamma]-site selectivity: The resulting, highly functionalized vinylogous Michael adducts, having two stereocenters at the [gamma] and [delta] positions, are synthesized with very high fidelity. Finally, we describe the extension of the dienamine catalysis-induced vinylogous nucleophilicity to the asymmetric [gamma]-amination of cyclohexene carbaldehyde. asymmetric synthesis | Michael reaction | organocatalysis doi/ 10.1073/pnas.1001150107

An efficient regio- and stereo-selective (>99:1) trans-bromohydrination (bromohydroxylation and bromomethoxylalion) of alkenes including α, β-unsaturated carbonyl compounds with N-bromosuccinimide (NBS) has been achieved by using 1,0 mol% of N,N'-diarylthiourea catalyst. Key words: thiourea, N'-halosuccinimide, alkene. On a pu realiser des broniohydrinations trans (bromohydroxylation et bromomethoxylation) d'alcenes regio- et stereo-selectives (>99:1) efficaces, y compris des composes carbonyles α,β-insatures, sous l'action du N-bromosuccinimide (NBS), en presence de 1,0 mole % de N,N'-diarylthiouree comme catalyseur. Mots-cles : thiouree, N-halosuccinimide, alcene. [Traduit par la Redaction], 1,2-Halofunctionalization of olefins, for example, halohydrin reaction (halohydroxylation and haloalkoxylation) is an important transformation in organic chemistry. (1) The resulting 1,2-halo hydroxy and alkoxyhalide compounds are versatile precursors in organic, [...]

Semifluorinated n-alkanes (SFAs) are anthropogenic chemicals that are used in ski waxes and, thus, are released directly into the environment, but their subsequent fate and distribution are as yet unknown. Therefore, simple, selective, and sensitive methods were developed for analyzing trace amounts of SFAs in snow/water, soil, and air samples by gas chromatography coupled to electron capture negative ionization mass spectrometry (GC/ECNIMS). Recoveries were generally in the range of 70-120%, depending on the compound and matrix. The analytical sensitivity was higher for SFAs with longer fluorinated chains, and the instrumental limits of detection ranged from 0.3 to 260 pg injected, providing method detection limits of 0.54-311 ng [L.sup.-1], 0.004-9.86 ng [g.sup.-1], and 0.4-531 ng [m.sup.-3] for snow (analyzed as its meltwater), soil, and air samples, respectively. Using the developed procedures, SFAs were found in snow (meltwater) and soil samples from a small cross-country ski area in Sweden at concentrations up to 1.3 [micro]g [L.sup.-1] and 47 pg [g.sup.-1], respectively. 10.1021/ac1005519

Yields of [beta]-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates, in particles formed from OH radical-initiated reactions of [C.sub.9]-[C.sub.15] 2-methyl-1-alkenes in the presence of N[O.sub.x] were measured by using a thermal desorption particle beam mass spectrometer coupled to a high-performance liquid chromatograph with a UV-visible (UV-vis) detector. Yields of [beta]-hydroxynitrates and dihydroxynitrates increased with carbon number primarily due to enhanced gas-to-particle partitioning before reaching plateaus at [approximately equal to][C.sub.14]-[C.sub.15], where the compounds were essentially entirely in the particle phase. Plateau yields of [beta]-hydroxynitrates, dihydroxynitrates, and trihydroxynitrates were 0.183 [+ or -] 0.005, 0.045 [+ or ] 0.005, and 0.034 [+ or -] 0.005, and, after normalization for OH radical addition to the C = C double bond, were 0.225 [+ or -] 0.007, 0.055 [+ or -] 0.006, and 0.042 [+ or -] 0.006. The fractions of 1-hydroxy and 2-hydroxy [beta]-hydroxynitrate isomers were 0.90/0.10. Yields measured here and in our previous study of reactions of linear internal alkenes and linear 1-alkenes indicate that, for these alkene classes, the relative branching ratios for forming tertiary, secondary, and primary [beta]-hydroxyalkyl radicals by OH radical addition to the C = C double bond are 4.3/1.9/1.0, and the branching ratios for forming [beta]-hydroxynitrates from reactions of tertiary, secondary, and primary [beta]-hydroxyperoxy radicals with NO are 0.25, 0.15, and 0.12. The effects of [H.sub.2]O vapor and N[H.sub.3] on yields were also explored. aerosol | atmospheric chemistry | organice nitrate | particles doi/ 10.1073/pnas.0910585107

The olefin cross-metathesis (CM) reaction is used extensively in organic chemistry and represents a powerful method for the selective synthesis of differentially substituted alkene products. Surprisingly, efforts to integrate this remarkable process into strategies for aromatic and heteroaromatic construction have not been reported. Such structures represent key elements of the majority of small molecule drug compounds; methods for the controlled preparation of highly substituted derivatives are essential to medicinal chemistry. Here we show that the olefin CM reaction, in combination with an acid cocatalyst or subsequent Heck arylation, provides a concise and flexible entry to 2,5-di- or 2,3,5-tri-substituted furans. These cascade processes portend further opportunities for the regiocontrolled preparation of other highly substituted aromatic and heteroaromatic classes. catalysis | cembranolide | Heck reaction doi/10.1073/pnas.0913466107

The Mizoroki-Heck reaction, which couples aryl halides with olefins, has been widely used to stitch together the carbogenic cores of numerous complex organic molecules. Given that the position-selective introduction of a halide onto an arene is not always straightforward, direct olefination of aryl carbon-hydrogen (C--H) bonds would obviate the inefficiencies associated with generating halide precursors or their equivalents. However, methods for carrying out such a reaction have suffered from narrow substrate scope and low positional selectivity. We report an operationally simple, atom-economical, carboxylate-directed Pd(II)-catalyzed C--H olefination reaction with phenylacetic acid and 3-phenylpropionic acid substrates, using oxygen at atmospheric pressure as the oxidant. The positional setectivity can be tuned by introducing amino acid derivatives as ligands. We demonstrate the versatility of the method through direct elaboration of commercial drug scaffolds and efficient syntheses of 2-tetralone and naphthoic acid natural product cores. 10.1126/science.1182512

Grafting of [W([equivalent to] NAr)(=CHtBu)[(2,5-[Me.sub.2]N[C.sub.4][H.sub.2]).sub.2]] on a silica partially dehydroxylated at 700[degrees]C (Si[O.sub.2]-(700)]) generates the corresponding monosiloxy complex [([equivalent to] SiO)W([equivalent to] NAr)(=CHtBu)(2,5-[Me.sub.2]N[C.sub.4][H.sub.2])] as the major species ([[approximately equal to] 90%) along with ([[equivalent to]SiO)W([equivalent to] NAr)(C[H.sub.2]tBu)[(2,5-[Me.sub.2]N[C.sub.4][H.sub.2]).sub.2]], according to mass balance analysis, IR, and NMR studies. This heterogeneous catalyst displays good activity and stability in the metathesis of propene. Very importantly, solid state NMR spectroscopy allows observation of the propagating alkylidene as well as stable metallacyclobutane intermediates. These species have the same reactivity as the initial surface complex [([equivalent to] SiO)W([equivalent to] NAr)(CHtBu)(2,5-[Me.sub.2]N[C.sub.4][H.sub.2])], which shows that they are the key intermediates of alkene metathesis. alkylidene | heterogeneous catalysis | metallacyclobutanes | solid state NMR

Different olefin partners in the presence of second generation Grubbs and Hoveyda-Grubbs precatalysts were used to prepare immobilized olefins as models for the cross metathesis. The results demonstrate that solid-phase cross metathesis is strongly dependent on the degree of homo-dimerization of the non-immobilized olefin and the reactivity of a homodimer.

The kinetics of hydrogen abstraction for the OH alkene reaction class using the reaction class transition state theory (RC-TST) along with the linear energy relationship (LER) and the barrier height grouping (BHG) approaches is investigated. It is concluded that the RC-TST /LER approach gives a better performance than the BHG.

The phase relationship of metastable orthorhombic phase and stable triclinic (T) phase for even-numbered carbon atom n-alkenes is investigated using toplological pressure-temperature (P-T) diagrams. The orthorhombic phase is found to show no stable phase region irrespective of the temperature and pressure.

A new method is described for preparing peptidyl ketones by using a Sm[I.sub.2]/[H.sub.2]O mediated coupling of N-peptidyl oxazolidinones with electron-deficient alkenes. This new method is an alternative means for ligating two small peptides through a C-C bond-forming step.

A photoinduced procedure is described for the intermolecular hydroamination of alkenes by using azoles. This mechanism has involved photoisomerization for generating highly strained (E)-cycloalkene intermediates and (E)-cycloalkene protonation followed by reaction with the azole nucleophile.

The substitution chemistry of olefin complexes [(silox).sub.3]M(olefin) (silox = [super t][Bu.sub.3]SiO; M = Nb, Ta) is examined. The disparity between Nb and Ta in olefin substitution chemistry is rationalized based on a greater density of states (DOS) for the products where M = Nb, leading to intersystem crossing events that has facilitated dissociation.

The orthogonal approach of the sequential copper- and palladium-mediated synthesis of 1,2-diarylindoles based on the use of diverse organoboron reagents is described.

The Diels-Alder reactions between variants of 2-trimethylsiloxycyclohexa-1,3-dienes with dienophile (E)-1,4-diphenylbut-2-ene-1,4-dione is described. The findings suggest that the electrostatic interaction between the oxygen lone pairs on the diene and the dienophile is critical to control the selectivity of elements.

A detailed computational study report on the ambiphilic acyl radicals, which could mask as electrophiles when added to electron-rich species that include imines and enamines, is presented.

Epoxidation catalysis can be controlled by examining the cooperativity between Bronsted acidic defect sites on oxide surfaces and Lewis acid catalyst sites consisting of grafted calixarene-Ti(IV) complexes. The sensitivity of epoxidation rates to the support oxide has provided evidence for the importance of outer-sphere H-bonding interactions for the exceptional epoxidation reactivity of titanium silicalite and related catalysts.

The alkane- and alkene-degrading, marine sulfate-reducing bacterium Desulfatibacillum aliphaticivorans strain CV2803 is examined for its 1-alkene metabolism. The pathways have indicated that diverse initial reactions of 1-alkene activation have occurred simultaneously in the same strain of sulfate-reducing bacterium.

The transient spectroscopic studies of the photocyclopropanation reaction between the C[H.sub.2]I-I isomer of C[H.sub.2][I.sub.2] and several cycloalkenes is reported. The cycloalkene ring size is found to have a modest effect on the reaction rate, while methyl substitution of the cyclohexene C=C bond has a more pronounced effect.

The photochemical reaction of terminal alkenes with hydrogen-terminated carbon surfaces is investigated. Results show that photoejection of electrons from the solid into the acceptor levels of the alkenes have initiated the functionalization reaction and have controlled the overall rate.

The article explains the regio- and stereocontrolled synthesis of various tetrasubstituted olefins with four different carbon-linked groups. These olefins are commonly used in the manufacture of various drugs.

Several studies are conducted for the characterization of the [H.sub.2]CO channel via 3,2 H-atom shift for the reactions of O([super 3]P) with terminal alkenes. The results prove that the fraction yield of [H.sub.2]CO product increases with higher alkenes.

The analysis explains the mechanism behind the addition of alkene to an oxidized ruthenium thiolate, which then helps in the formation of a bond between carbon and sulfur atoms. In spite of being extremely advantageous, the complexes fail to show any reduction within the solvent.

A short synthesis of gabosine I from [delta]-D-gluconolactone is achieved in four steps, which has involved a one-pot TPAP oxidation-[K.sub.2]-C[O.sub.3]-mediated intramolecular Horner-Wadsworth-Emmons (HWE) olefination as the key step. The regioselective acetylation of the primary alcohol in gabosine I have furnished gabosine G.

Solid-state NMR and infrared (IR) measurements are combined with computational analysis to examine the structures of major sites formed by grafting C[H.sub.3]Re[O.sub.3] onto amorphous silica-alumina and their relationships with olefin metathesis activity of this material. The results have suggested simple modifications in catalyst preparation, which has led to higher selectivity, less leaching and efficient use of the Re complex.

The scope of the four-step mechanism for [d.sup.0] complexes and the factors that favor the olefin metathesis reaction are evaluated by studying the influence of the metal (Mo, W and Re), the imido vs. the alkylidyne and the X and Y spectator ligands. The results have shown that the Re complexes are less efficient than the Mo and W catalysts, except when Re is unsymmetrically substituted.

The viability of alkene metathesis in platinum coordination spheres is established along with other reactions for the construction of novel sterically shielding polyynediyl complexes. The results have shown that complexes with termini-spanning diphosphines show [sp.sup.3] chains with both double-helical and non-helical conformations and highly shielded sp chains.

Methylidene species are used as model complexes for examining the decomposition of a series of ruthenium metathesis catalysts. The decomposition study has provided a basis for design and synthesis of more efficient ruthenium olefin metathesis catalysts.

The stereochemistry of the aminopalladation step of various different catalyst systems of alkenes with two-faced reactivity is studied to analyze and report the cis- versus trans-aminopalladation in several aerobic Pd-catalyzed intramolecular Aza-Wacker reactions. The analysis reveals that the nitrogen nucleophile in such systems highly affect the aminopalladation pathway, hence leading to successful oxidative amination of alkenes.

The study presents a mechanistic research and investigation of intramolecular aminoalkene and aminoalkyne hydroamination/cyclization that is normally catalyzed by several highly electrophilic and tetravalent constrained geometry complexes. The existence of identical reactivity trends, rate laws and activation parameters of the complexes prove the formation of an M-N [sigma]-bonded insertive pathway in the substance.

The reaction mechanism of the copper(II) carboxylate-promoted intramolecular carboamination of unactivated alkenes has provided a means to N-functionalized pyrrolidines and piperidines. The results have supported the mechanism wherein the N-C bond is formed through intramolecular syn aminocupration and the C-C bond is formed via intramolecular addition of a primary carbon radical to an aromatic ring.

Exo-triazolines are prepared by adding azides to acylnitroso hetero-Diels-Alder cycloadducts that are derived from cyclopentadiene. The steric bulk of the azide has no significant role in the course of reaction, but the reactivity of the alkene is diminished significantly in cycloadducts derived from larger cyclic dienes or in monocyclic alkenes.

The study of the titanocene(II)-promoted stereoselective alkenylation utilizing (Z)-alkenyl sulfones, is presented. It is shown that the described alkenylation system leads to the production of various conjugated dienes, polar bonds and several carbonyl compounds and sulfones.

An easy, green two-step, quasi-one-pot synthetic method to bidentate Schiff base substituted ruthenium carbene complexes with silver carbonate as base is presented. It is found that the target ruthenium carbene complexes are same or better as compared to the original method.

The regioselective palladium-catalyzed formate reduction of allylic acetates in five- to eight-membered heterocycles to transform the endo-olefin to the exo-position is described. The palladium-catalyzed formate reductions of allylic substrates are an effective method to isomerize the endocyclic olefin formed by ring-closing metathesis (RCM) to the exo-position.