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The oxidation of cyclohexene with tert -butylhydroperoxide (TBHP) in the presence of exchanged zeolite NaY (NaA and HS in some cases) with transition metal elements Cr(III), Mn(II), Fe(III), Co(II), Ni(II) and Cu(II) in refluxing dichloromethane has been investigated. The results showed that the Mn–Na–Zeolite had the highest reactivity and selectivity with the formation of di(2-cyclohexenyl) ether as the main product. The optimum conditions were applied to cyclopentene and 1,1-diphenylethylene which afforded di(2-cyclopentenyl) ether and benzophenone, respectively.

The molecular geometries of different conformations of cycloalkenes, C n H 2 n -2 , with n = 5, 7 and 8 were optimized by restricted Hartree-Fock calculations using the 6–31G∗ basis set followed by second-order Moller-Plesset perturbation theory (MP2) treatment of electron correlation. For cyclopentene, C 5 H 8 , the potential function for the ring-puckering motion was constructed, followed by solving for the vibrational eigenvalues in terms of distributed Gaussian bases. Good agreement was obtained with the observed frequencies in the far-infrared spectrum of the molecule. For cycloheptene, C 7 H 12 , geometries were optimized for the chair, boat, twist-boat, and three possible transition states. The chair-chair interconversion mechanism was investigated and compared with available experimental evidence and with the results of a previous molecular mechanics calculation. The computed potential barrier compares well with NMR evidence, but the conformation of the relevant transition state is found to be different from the one assumed in the experimental study. The structure of the smallest isolable trans -cycloalkene, trans -cyclooctene, C 8 H 14 , was optimized, yielding a structure in reasonable agreement with a previous gas phase electron diffraction study. The agreement includes the pyramidality of the olefinic carbon atoms which was also compared with available X-ray data on related compounds. The bond angles and torsion angles were in better agreement with the experiment than were those obtained in earlier molecular mechanics studies, although it is remarkable how well that method works for these highly strained cyclic systems.

The surface chemistry of cycloalkanes and cycloalkyl intermediates on Pt-Sn alloys is important to the function of selective hydrocarbon conversion catalysts, yet very little is known about this chemistry because cycloalkane decomposition is strongly suppressed under UHV conditions on Pt-Sn alloys and there are few other clean sources of these intermediates. Low-energy, electron-induced dissociation (EID) in multilayers of saturated hydrocarbons produces rather cleanly reactive intermediates formed by the selective cleavage of one C-H bond. This method was used to activate C 5 -C 8 cycloalkane multilayers and prepare monolayer coverages of cycloalkyl species on Pt(111) and two well-defined Pt-Sn alloy surfaces-the p(2 x 2)-Sn/Pt(111) and (√3x √3)R30°Sn/Pt(111) surface alloys formed by vapor deposition of Sn on a Pt(111) substrate. EID of the multilayers and subsequent thermal reactions of the intermediates on these surfaces were investigated by temperature-programmed desorption (TPD), Auger electron spectroscopy (AES), and low-energy electron diffraction (LEED). Adsorbed cycloalkyl species dehydrogenate facilely on both alloy surfaces, but alloying with Sn weakens the bonding to the surface of the cycloalkenes formed and strongly suppresses cycloalkene dehydrogenation. This chemistry leads to a much higher selectivity for the evolution of gas-phase cycloalkenes from the dehydrogenation of cycloalkyl intermediates compared to that on Pt(111).

Retention indices or five 1-alkenes, seven branched alkenes and five cycloalkenes and the corresponding epoxides were determined at two temperatures on a fused-silica capillary column coated with cyanopropyl methyl siloxane to interpret their chromatographic behaviour. The standard deviation was 0.2 index units.

Epoxidation of cis-cyclooctene with iodosylbenzene has been carried out in the absence and presence of metal complex catalysts and light. Increase in the epoxide yield is observed in the presence of light.

A 1% w/w Pt/sulphated zirconia derived from a zirconia hydrogel and having high metal dispersion (arising from having an oxidative redispersion stage in the preparation) is active for skeletal reaction of n-pentane and of methylcyclopentane (MCP) at and above room temperature. A number of tests show that this high activity derives from the classical dualfunctionality of the catalyst. Implicitly, therefore, spillover of alkene or cycloalkene to and from the metal surface takes place at or near room temperature. Experiments with this catalyst and with Pt/zirconia show values of the 2MP/3MP product ratio for the MCP ring opening reaction much greater than the statistical value of 2.0. The effect derives from the Pt/zirconia combination in contrast with Pt on more usual supports (silica, alumina, magnesia, titania). The presence of the electronegative constituent sulphate does not lead to a significantly higher 2MP/3MP ratio than for Pt/zirconia itself. There is adequate correlation of the high 2MP/3MP ratio feature with an initial product pattern of major D2-isomer (alongside D5) in the exchange reaction between cyclopentane and deuterium conducted at lower temperatures on identical batches of the same catalysts so as to suggest the following rationale. This deuterium pattern is known to be associated with the action of electron deficient platinum sites. For MCP ring scission, requiring a site pair, such platinum sites may act catalytically in concert with normal Pt0 sites. The electrical asymmetry of such a platinum neighbour-site pair leads to a polar transition state which favours the asymmetric ring scission of MCP to 2MP, rather than to 3MP, akin to other well-known examples among retro-[2+2] reactions. It is proposed that this electrical asymmetry in a pair site can be furnished by a platinum atom atop a surface ensemble (and therefore topographically electron deficient) and a nearest-neighbour (electrically normal) platinum atom.

Evidence presented in this paper suggests that transformations from simple alkenes to homologs can be facile via the pathway outlined. Use of platinum and other metals (Rh) can provide an element of control to the process that does not exist with other processes using acids or heat directly on the hydrocarbon substrate. The evidence derived from the substrates investigated indicates that control of the reaction may be achieved so as to produce high chemoselectivity or even chemospecificity for olefin homologation. Mechanistic evidence indicates that exocyclic methylene and methyl-cycloalkene products follow a pathway that involves an initial alpha hydride transfer step. It is important to note that there is ample precedent suggesting that the isolated platinacyclic complex may not be the complex that yields the observed products, but rather an intermediate platinacycle derived from a ‘Puddephatt rearrangement’ is the pre-product complex. Finally, a pathway involving a carbocationic intermediate is proposed for the ring-homologation reaction for the acenaphthalene to pinenalene transformation.

Synthesis of two retinoids in which the 9,13-dicis double bonds were locked in cycloalkene or thiophene was described. The key step was carbonylation of vinyl bromide 9 and 16 with carbon monoxide in the presence of Pd(PPh 3 ) 4 . © 1997 Elsevier Science Ltd.

A series of α-fluorobicyclopropyl radicals were generated by the reaction of CF with the corresponding cycloalkene. The tendency of these radicals to undergo electrocyclic ring opening to the corresponding cyclic allyl radicals was evaluated computationally and experimentally. The symmetry forbidden ring openings will occur if there is significant thermodynamic driving force. AM1 calculations and product analysis indicate that those radicals with calculated ring opening exothermicities of 50 kcal/mol or more give ring opened products © 1997 Elsevier Science Ltd.

Six novel 1,2-bis(1-alkyl-2-methylindol-3-yl)cycloalkene derivatives were designed and synthesized by the intramolecular coupling reaction using low-valance titanium as catalyst. Photochromic properties of these compounds were initially investigated. The results show that the fatigue resistant properties of these compounds, the thermal stability and the absorption maxima of their photocyclization products are influenced by the ring size of cycloalkene and substituents on the heterocyclic rings.

The ozonolytic cleavage of cycloalkene in the presence of methyl pyruvate affords a tri-substituted ozonide. The resulted tri-substituted ozonide moiety contained three reactive centers (i.e. peroxide, ozonide ring proton and methoxycarbonyl group) which could be transformed to different functional groups under different conditions in good yields. It is a very efficient and versatile methodology to prepare the terminal differentiated compounds from symmetric cycloalkenes in two steps in high yields.

We report here the hydrogenation of cycloalkenes using Rh-supported montmorillonite as a catalyst. The catalyst preparation was based on oxidative degradation of intercalatedtris(phenanthroline)-Rh (III) followed by reduction under hydrogen atmosphere. No obvious trend is seen in the hydrogenation yields of the olefins though cyclopentene and cyclooctene are reduced faster than cyclohexene and cycloheptene. 2-Cyclohexen-1-one reacts marginally faster than cyclohexene under similar conditions. When the hydrogenation experiments were repeated employing binary mixtures of the olefins, considerable differences in hydrogenation behaviour were observed over that found when the olefins were taken in their pure form. The most notable difference in the hydrogenation behaviour of binary mixtures was observed in the case of cyclopentene/cyclooctene: both olefins could be efficiently hydrogenated in their pure form but there was no conversion of cyclooctene in presence of cyclopentene.

Fluxes and separation factors are reported for the facilitated transport of a variety of C6 alkenes and dienes through two Ag(I)-exchanged polyfluorosulfonate ionomer membranes. For acyclic dienes, the largest separation factors are observed between those compounds with the greatest difference in spacing of the double bonds, and those with completely external versus internal double bonds. For cases where the spacing of the double bonds is the same, the compound with at least one terminal double bond exhibited a higher flux. The trends in fluxes for cyclic dienes is quite different; 1,4-cyclohexadiene is transported more slowly than cyclohexene while 1,3-cyclohexadiene is transported almost eight times more rapidly than cyclohexene. Methyl-substituents on the carbons comprising double bonds have minor effects on the transport properties. As anticipated, PFSI materials that contain more ion-exchange sites and absorb greater quantities of water exhibit slightly greater fluxes and separation factors for most alkene separations.

The kinetics of the gas-phase reactions of ozone with a series of cycloalkenes have been investigated using a conventional static system. Ozone loss was monitored in the presence of excess cycloalkene and rate data measured over the temperature range 240–331 K. Rate constants for the reactions of ozone with C 5 –C 8 cycloalkenes and several substituted cyclopentenes and cyclohexenes at 298 K were determined and Arrhenius parameters were also calculated from the experimental data. The rate parameters obtained in this study are compared with previous literature data and discussed in terms of structure–reactivity relationships.

To elucidate the mode of action of chromosaponin I (CSI) in stimulating the growth of lettuce roots (Lactuca sativa L. cv. Grand Rapids), the possible involvement of ethylene was examined. Lettuce seedlings evolved ethylene at a rate of 0.7 nl 10 seeds-1 h-1. The growth of lettuce roots was stimulated by 2-aminoethoxyvinyl-glycine (AVG), an inhibitor of ethylene synthesis, and 2,5-norbornadiene (NBD), an inhibitor of ethylene action, as well as by CSI. In contrast to ethylene, treatments with CSI, AVG and NBD promoted longitudinal elongation of cortical cells of roots and inhibited their lateral expansion. Application of CSI slightly reduced ethylene production from lettuce, but this reduction was not sufficient to account for the CSI-induced stimulation of growth. The maximal promotive effects of AVG and NBD were obtained at 3 micromolar and 150 microliters, respectively. The growth promotion by CSI disappeared in the presence of the optimum levels of AVG or NBD; a further addition of ethylene caused the stimulatory effects of CSI to increase, depending on the concentration of ethylene. Thus, CSI reduced both the sensitivity of the roots to ethylene and the maximal effects of ethylene. The CSI-induced stimulation of growth was ascribed to the reduction of the response to ethylene in the lettuce roots.

Radical anions of 2,3-diazabicyclo[2.2.1]hept-2-ene 1 and its 18 substituted and tricyclic derivatives (2a–11c) have been characterized by their hyperfine data with the use of EPR and ENDOR spectroscopy. The structural modifications of 1, yielding 2a–11c, are methyl and/or phenyl substitutions in the 1,4-positions, introduction of methyl groups or a spirocyclopentane ring in the 7,7-positions and annelation by a cyclopropane, cyclobutane, cyclobutene, cyclopentane or cyclopentene ring in the 5,6-endo-positions. Although these modifications do not markedly alter the π-spin and charge distribution in 1˙-, they have a strong effect on the long-range coupling constant of the γ-protons in the 5,6-exo-positions: the pertinent aH(γ) value varies from +0.26 to +0.64 mT. The effect is particularly impressive for the 5,6-endo-annelation by a cycloalkane or a cycloalkene ring and it goes along with only slight changes in the geometry of the carbon framework in 1˙-. Thus, owing to the through-bond mechanism of π,σ-spin transfer (homohyperconjugation), the coupling constant, aH(γ), of the 5,6-exo-protons responds sensitively to such changes in the geometry.

International audience; A simple sequence for the net contra-thermodynamic isomerization of cyclic trisubstituted alkenes is reported consisting of a radical addition of p-chlorothiophenol, followed by oxidation to the sulfoxide and thermal syn-elimination to give the least substituted isomeric cycloalkene.

A central idea in organic chemistry for the past 50 years is that cyclopropenyl anion is antiaromatic. A correlation between cycloalkene acidities and allylic bond angles reveals that energetically this is not case, cyclopropenyl anion is nonaromatic.

An aryl Grignard reagent in the presence of mesityl iodide converts an allylic C-H bond of a cycloalkene or an allylbenzene derivative into a C-C bond in the presence of a catalytic amount of Fe(acac)(3) and a diphosphine ligand at 0 °C. The stereo- and regioselectivity of the reaction, together with deuterium labeling experiments, suggest that C-H bond activation is the slow step in the catalytic cycle preceding the formation of an allyliron intermediate.

Metal-free synthesis: Diamination of alkenes by using phenylhydrazine and azodicarboxylates could be achieved in a one-pot manner under very mild conditions (see scheme; Boc = tert-butoxycarbonyl). This process works with the assistance of acetic acid by means of a radical mechanism and displays a high trans selectivity when cycloalkene substrates were used in the reaction.

In this paper we report the synthesis of new compounds based on the pyrazole and isoxazole framework fused to a cycloalkene unit, and bearing as a substituent the 1-piperidinyl group as new examples of potential antipsychotic molecules. The general synthesis involves the acylation of a chloro-substituted cyclic ketone with a 1-substituted piperidine-4-carboxylate derivative, followed by heterocyclization of the formed 1,3-dioxo compound with a hydrazine or hydroxylamine. © 2013 by the authors.

Molybdovanadophosphate (NPMoV)/hydroquinone/O 2 system was found to be an efficient reoxidation system in palladium-catalyzed oxidations of alkenes and related compounds. Thus, acetoxylations of cycloalkenes utilizing molecular oxygen as the final oxidant were cleanly performed using the multicatalytic system consisting of Pd(OAc) 2 /hydroquinone/NPMoV to form 3-acetoxy-1-cycloalkenes in good yields. For example, cyclopentene and cyclohexene were converted into the corresponding allylic acetates in almost quantitative yields. Omitting hydroquinone from the catalytic system led to low yields of the acetates. Acetoxylation of cyclooctene was satisfactorily achieved by replacing hydroquinone of the multicatalytic system by chlorohydroquinone. Molybdovanadophosphates, which catalyze the smooth dehydrogenation of hydroquinone to benzoquinone with dioxygen, were found to rapidly promote the present Pd(II)-catalyzed acetoxylation of cycloalkenes. By the use of a mixed solvent of ethanol and water under these conditions, Wacker type oxidations of cyclohexene and styrene were accomplished in fair to good yields. Monosubstituted alkenes such as ethyl acrylate and acrylonitrile underwent the acetalization by the present catalytic system to give the corresponding acetals in quantitative yields.

Magnesium oxide supported polytitazane cobalt (III) complex is demonstrated as an effective catalyst for the epoxidation of cis-cyclooctene with molecular oxygen at atmospheric pressure in the presence of isobutyraldehyde as the sacrificial reductant. XPS data show that the high-valent cobalt (III) is stabilized by the multidentate nitrogen ligand of polytitazane. The conversion of cis-cyclooctene is as high as 95.2% with 100% selectivity to the cis-cyclooctene oxide at 25°C within 5 h. The catalyst can be used at least nine times without loss of its activity. Ein auf Magnesiumoxid aufgebrachter Polytitazan-Cobalt (III)-Komplex diente als effektiver Katalysator fur die Epoxidierung von cis-Cycloocten mit molekularem Sauerstoff bei Normaldruck in Gegenwart von Isobutyraldehyd als Reduktionsmittel. Nach XPS-Untersuchungen wird Cobalt (III) durch den mehrzahnigen Stickstoffliganden des Polytitazans stabilisiert. Bei 25°C betragt der cis-Cycloocten-Umsatz nach funf Stunden 95,2%, mit einer Selektivitat von 100% fur das cis-Cyclohexylenoxid. Der Katalysator Kann mindestens neun Mal ohne Aktivitatsverlust verwendet werden.

On the basis of the hydropalladation and chloropalladation of the carbon−carbon triple bond, [PdH] and [PdCl] active species were employed to catalyze the cyclization of homoallylic 2-alkynoates and ω-alken-2-ynoates. From homoallylic alkynoates, two kinds of α-alkylidene-δ-valerolactone derivatives showing different stereochemistries of the exocyclic alkylidene double bond were obtained using two catalytic systems, while from the latter, hydropalladation and chloropalladation showed opposite regioselectivity, giving bis(alkylidene)cycloalkane and cycloalkene derivatives, respectively.

Poly(vinylbenzyl)acetylacetonato complex of cobalt is an effective and stable catalyst for the epoxidation of cycloalkenes with molecular oxygen under 25°C with i-butyraldehyde as the sacrificial reductant. The acetylacetone ligand/Co mole ratio, the reaction time, and the strain and electronic nature of cycloalkenes all affect the conversions of alkenes and selectivities to the corresponding epoxides. The catalyst can be recycled at least seven times without loss of its activity.

Synthesis of bishomohexaprimanedione, the D 2h dimer of norbornadienone and a potential precursor to hexaprismane, is reported. The synthesis includes an unusual ring contraction of a cycloalkene using a cis -hydroxylation/periodate cleavage/aldol sequence. The structure of bishomohexaprimanedione determined from single crystal x-ray analysis is well reproduced by ab initio calculations.

International audience; In this work, structure H hydrate phase equilibrium of hydrogen in the presence of organic promoter is predicted using a proposed thermodynamic model. The investigated promoters are various n-alkanes, n-alkenes/alkynes, and cycloalkanes/cycloalkene. The van der Waals-Platteeuw solid solution theory is used for determination of the fugacity of water in hydrate phase. Phase behavior of the hydrogen+water system is modeled using the Valerama-Patel-Teja equation of state (VPT-EoS) with non-density dependent mixing rules. Due to the lack of experimental solubility data of hydrogen in the investigated promoters, the phase equilibria of the hydrogen+promoter system is treated using the VPT-EoS-G E method consisting the UNIFAC activity model and the modified Huron-Vidal (MHV1) mixing rules. The obtained results show reasonable agreement of the predictions with the existing experimental data from the literature. Finally, the hydrogen storage capacity of the corresponding clathrate hydrates is predicted as well as the occupancies of the clathrate hydrate cavities.

Mo(VI) has been supported on a polybenzimidazole resin and used as an epoxidation catalyst in the reaction of t -butylhydroperoxide (TBHP) with cyclohexene. A preliminary kinetic study has suggested that mass transfer of TBHP might be rate-limiting. The experimental activation energy is higher than that of an analogous homogeneous reaction catalysed by MoO 2 acac 2 . Nevertheless, the supported catalyst is highly active and has been recycled nine times with no detectable loss of Mo from the support, but with a decline in activity. Activation of the polymer catalyst by pretreatment with TBHP far periods up to 48 h does not influence the activity of the catalyst on first use; however, higher activity is retained on recycling. The imidazole ligand on the polymer appears to bind the Mo centres very effectively and Mo leaching is not responsible for the decay in activity on recycling. The most likely explanation for this is the blockage of access to catalytic sites in the polymer by accumulation of side-products (oligomer) from cyclohexene or its epoxide.

Several difurylperfluorocyclobutenes showing reversible photochromism were synthesized. In comparison to their cyclopentene homologues they show enhanced quantum yields for ring opening but reduced quantum yields for ring closure. X-ray structure analysis and quantum chemical calculations provide a conclusive explanation for such a behaviour.

The conversion of substituted 2-hydroxy-1,4-benzoquinones, 1, to 2-cyclopentene-1,4-diones, 3, is effected by thermolysis of their iodonium zwitterions, 2. Some cycloadditions through 2 are also described.

Reactivity, regioselectivity and stereoselectivity of the addition reaction between tetrachloromethane and C 5 to C 10 cycloalkenes in the presence of copper, ruthenium, molybdenum, cobalt and iron complexes as catalysts and dibenzoyl peroxide as an initiator have been examined in the temperature range 22 to 80°C. Relative reactivities of the cycloalkenes decreased in sequence C 8 >C 5 >C 7 >C 6 >C 10 . These rates were not strongly affected by the catalysts indicating that the reactivities of cycloalkenes are mainly controlled by I-strain in the cycloalkene molecule. Transannular addition was observed in the reactions of cis -cyclooctene and cis -cyclodecene. The ratio of transannular to vicinal addition was significantly lowered by [RuCl 2 (PPh 3 ) 3 ] and [CuCl(NHEt 2 ) 2 ], in comparison with dibenzoyl peroxide. A strong catalyst effect on the stereoselectivity of the addition reaction of cyclohexene was also recorded. The trans:cis isomer ratio of the adduct was significantly affected by ruthenium catalysts and, to lesser extent, by copper, molybdenum, cobalt and iron catalysts. The catalyst effect on regioselectivity and stereoselectivity strongly support a non-chain mechanism involving coordination of reactants and product formation at the metal centre in contrast to the classical initiation of chain reactions by organic peroxides.

The reaction of cyclopentadiene with 1,1,3,3-tetrakis(methoxycarbonyl)propene gives an endo and exo mixture of dimethyl 2-{3,3-bis(methoxycarbonyl)bicyclo-[2.2.1]hept-5-en-2-yl}malonate, which by base-mediated retro-Michael reaction gives stereoselectively the cis-isomer of dimethyl 2-{4-[2,2-bis(methoxycarbonyl)vinyl]cyclopent-2-en-1-yl}malonate.

An efficient allylic and benzylic oxidation of various cyclic alkenes and benzylic compounds respectively can be achieved with dioxygen in the presence of ethyl 2-oxocyclopentanecarboxylate 2 and catalytic amount of cobalt(II) Schiff's base complex 1.

Stereospecific annulation of cyclic alkenes for the preparation of cis-fused seven-membered ring systems was accomplished by sequential [2 + 2] cycloaddition, exo-allylation, hydrohalogenation, and free radical ring expansion. The new strategy extends our recently developed cyclobutanone-based ring expansion reactions.

Homogeneous catalysts WCl 6 —1,1,3,3-tetramethyl-1,3-disilacyclobutane and WCl 6 —dihydrodiphenylsilane allow cross-metathesis of cycloolefins (cyclopentene, cyclooctene) and norbornene with ethyl-4-pentenoate, allyl cyanide, allyltrimethylsilane. Self-metathesis of functionalized olefins with two unconjugated carbon—carbon bonds takes place with high yields and selectivity.

1,2-Dichlorotetrafluorocyclobutene (A) and 1,2-dichlorohexafluorocylopentene-1 (B) were reacted with triazamacrocyclic amines (1,4,8-triazacycloundecane (1) and 1,5,9-triazacyclo-dodecane (2)) at 80 °C in the presence of stoichiometric amounts of triethylamine in benzene. Cycloalkene A formed a 2:1 product 3 with 1 and a 3:1 product 4 with 2. Cycloalkene B formed only 2:1 products 5 and 6 with 1 and 2, respectively. The crystal structures of 3 and 4 were determined by single-crystal X-ray diffraction.

The reactivities and reaction pathways of C 7 alkenes over a CoMo/Al 2 O 3 hydrotreating catalyst were studied using both model compound feeds and heavy catalytic naphtha (HCN). The three C 7 compounds studied included a normal alkene (1-heptene), an isoalkene (2-methyl-1-hexene), and a cycloalkene (1-methylcyclohexene). All three compounds underwent double bond isomerization and hydrogenation, but only the iso- and cycloalkenes reacted by skeletal isomerization. No appreciable amounts of cyclization products were observed. The rates of hydrogenation were of the order normal alkenes (heptenes) > isoalkenes (methylhexenes) > cycloalkenes (methylcyclohexenes). The distributions of the unconverted alkenes for each type of compound generally approached predicted equilibrium values as the reaction temperature increased

5,5'-bi-1,2,4-Triazines undergo inverse electron demand Diels-Alder reaction with 1-vinylimidazole to give single [4+2] cycloaddition products. The reaction of the latter with cyclic enamines leads to unsymmetrical, 2,2'-bipyridines with attached cycloalkene ring.

The possibility of ring strain as the cause of bond localization in metalloarene-fused octadehydro[14]annulenes is addressed. It was found that strain-induced bond localization is not observable in the mildly aromatic annulenes previously used to compare the degree of delocalization in CpCo(cyclobutadiene) relative to ferrocene and benzene.

The NO3 radical initiated oxidation of cyclopentene, cyclohexene and 1-methyl-cyclohexene has been studied. The products formed in an N2O5-NO2-N2-O2-cycloalkene-static reactor system, at 0.1 MPa and 296 K, were investigated using long path FTIR. The principal products were aldehydes formed via a ring opening process. The reactions also resulted in significant yields of three types of ring retaining nitrooxy-substituted compounds. The average yields of alkyl nitrates from, e.g., reactions with cycloalkene were 25.1% 2-oxo-cyclohexyl nitrate, 22.8% 2-hydroxy-cyclohexyl nitrate and 4.0% 1,2-cyclohexyl dinitrate. The mechanisms involved resembles those proposed for acyclic alkenes. In absence of NO, α-oxo and α-hydroxy-cycloalkyl nitrates are formed via self reactions of α-nitrooxy substituted cycloalkyl peroxy radicals. Estimated branching ratios for the reactants leading to ring retaining products in the presence and in the absence of NO are given and the possible relevance of these reactions for cycloalkenes under tropospheric conditions is discussed.

The ozonolytic cleavage of cycloalkenes in the presence of methyl pyruvate affords the tri-substituted ozonides. These ozonides possess triple reactive sites which could be converted to several terminally differentiated products via reduction or base treatment.

Reaction of ozone with three kinds of olefins in air was studied. H2O2, CH3OOH, and HOCH2OOH were collected and analyzed with HPLC with a fluorometric detector. Direct reaction of CH2OO with H2O was found to be the source of HOCH2OOH. CH3OOH was formed only from the olefins which have a methyl group. Detailed reaction mechanisms are discussed.

An efficient synthesis of (±)-carbovir 1 and simple des(hydroxymethyl) analogues, e.g., 5 , is reported which uses a new approach for attaching nucleoside bases to cycloalkene systems.

The two antipodes of 1-bromo-3,3-dimethyl-4-[(tert-butyldimethylsilyl)oxy] cyclopentene, the dextrorotatory form of which (1) is regarded as a potential synthetic precursor to kalmanol, have been prepared in a state of high enantiomeric purity from propargyl alcohol. The key steps in the abbreviated synthetic pathway involve the bromination-dehydrobromination of 3-(trimethylsilyl)propenal 12 to give 2-bromo-3-(trimethylsilyl)propenal 7, the conversion of 2-bromo-3-(trimethylsilyl)propen-1-ol 13 to the 1-bromo-3,3-dimethylcyclopenten-4-ol 18 by a novel tandem Claisen-Sakurai reaction sequence, and efficient enzymatic resolution of 18 via its chloroacetate ester. The absolute configurational assignments are based on 1 H NMR analyses of the (R)- and (S)-MTPA esters of (-)-20

Four chelating resins derived from crosslinked poly(chloromethylstyrene) (PCMS), four derived from crosslinked poly(glycidylmethacrylate) (PGMA), and one crosslinked poly(4-vinylpyridine) resin have been used to immobilise Mo complexes. The metal centre was introduced to the polymeric ligands by ligand exchange using MoO2(acac)2. The initially blue-coloured polymers were activated by treatment with excess tert-butylhydroperoxide to yield bright yellow resins, and it is believed that oxidation of Mo(V) to Mo(VI) occurs during this process. Each resin was then employed as a catalyst in the solution epoxidation of cyclohexene using tert-butylhydroperoxide as the oxidant at ∼ 80°C. In all cases, the resin catalysts were highly active with the PGMA-based species being consistently more active, possibly due to its higher polarity and more favourable morphology. Extensive studies of the recycling of the various catalysts with monitoring of the level of Mo leaching in each reaction showed that more stable complexes were obtained with chelating ligands with two or more nitrogen donor sites. In the case of PCMS-based resin with an N-(2-hydroxypropyl)aminomethyl-2-pyridine ligand complexed with Mo(VI) with a ligand/metal ratio of ∼ 1 2 , the stability of the resin complex allowed recycling nine times without any loss of activity, and with the corresponding level of Mo leaching falling essentially to zero. In contrast, an analogous resin with a ligand/metal ratio of 1 2 displayed Mo leaching which increased on recycling.

The cross-coupling reaction of 9-alkyl-9-borabicyclo[3.3.1]nonane (9-R-9-BBN), 1-alkenyl-1,3,2-benzodioxaborole, or aryl boronic acid with 1-alkenyl or aryl triflates in the presence of K 3 PO 4 (1.5 equiv) and a catalytic amount of Pd(PPh 3 ) 4 or Cl 2 Pd(dppf) resulted in high yields. The reaction conditions are sufficiently mild so that a variety of functionalized alkenes, alkadienes, and arenes are readily obtained. The utility of the present reaction was demonstrated by the cyclization of ω-alkenyl triflates leading to a benzo-fused cycloalkene and bicyclic alkene via a hydroboration-intramolecular coupling sequence

The stochastic search method coupled to MM3(92) has been used to locate as many conformers as possible for 6- to 11-membered ring lactones, trans-cycloalkenes, and cis-cycloalkenes. A comparison was carried out between the conformers of lactones and cycloalkenes of the same ring size for each force field. These comparisons were carried out by means of (1) conformational distances, defined as the rms deviation between the dihedral angles of the conformers being compared, and (2), substitution, in which a lactone was transformed into an olefin and vice versa, trying to keep as much as possible the initial geometry, followed by reoptimization. It is found that cycloalkenes and lactones share many common characteristics. The thermodynamic information provided by MM3 was used to study the dependence of conformer population upon (1) temperature and (2) total number of conformers. © 1993 John Wiley & Sons, Inc.

Thermolysis of 3-acetylcyclobutene resulted in a mixture of E-and Z-dienes, favoring slightly the E-diene, in accord with theoretical prediction. This preference was reversed by the Lewis acid, ZnI 2 , also predicted by ab initio calculations on a model system.