693-89-0

The title compound has been prepared in 70% yield by the reaction between 1-chloro-1-methylcyclopentane and deuterotributylstannane, without solvent. Small amounts (0.7-3.5%) of unreacted starting material remained after the reaction and were removed by solvolytic HCl elimination with water or aqueous sodium hydroxide, followed by oxidation with potassium permanganate or bromine addition at low temperature, which form products of low volatility. Small amounts of a by-product, deuterobutane, resulting from the cleavage of the carbon-tin bond in the reactant were also observed in the product.

Heterolysis of 1-methyl-1-chlorocyclopentane in protic and aprotic solvents occurs by the E1 mechanism. The reaction rate in aprotic solvents or in a set of protic and aprotic solvents is satisfactorily described by the parameters of the polarity and electrophilicity or ionizing power of the solvents. In protic solvents, the reaction rate grows with increasing polarity or ionizing power of the solvent and decreases with increasing nucleophilicity.

The synthesis of two nickel hydride complexes bearing the pyrrole-derived phosphine ligand CyPNH (2-(dicyclohexylphosphino)methyl-1H-pyrrole) was developed, namely, (κP-CyPNH)(κP,κN-CyPN)NiH and the acid-stable trans-(κP-CyPNH)2Ni(OAc)H·HOAc. (κP-CyPNH)(κP,κN-CyPN)NiH stoichiometrically reduces benzaldehyde and acetophenone in a metal-ligand cooperative manner and catalytically dimerizes ethylene and cycloisomerizes 1,5-cyclooctadiene and 1,5-hexadiene. trans-(κP-CyPNH)2Ni(OAc)H·HOAc, available from the protonation of (κP-CyPNH)(κP,κN-CyPN)NiH with acetic acid, catalyzes the cycloisomerization of 1,5-cyclooctadiene more effectively and produces the less thermodynamically favored cycloisomers of 1,5-cyclooctadiene.

The invention relates to methods of hydrodeoxygenation of oxygenated compounds into compounds with unsaturated carbon-carbon bonds, comprising the steps of: a) providing a reaction mixture comprising, an oxygenated compound containing one or more of a hydroxyl, keto or aldehyde group, an ionic liquid, a homogeneous metal catalyst, and carbon monoxide or a carbon monoxide releasing compound, b) reacting said reaction mixture under a H2 atmosphere at acidic conditions at a temperature between 180 and 250 °C and a pressure between 10 and 200 bar.

The invention discloses trans - 2 - substituted cyclohexyl three fluoro potassium borate synthesis method, which belongs to the field of organic synthesis. From the cyclic ketone starting curing and reagent or lithium reagent addition subsequently dehydrated and gets substituted alkenes, subsequently with the catechol borane or after aminol borane addition reaction, fluorine hydride potassium direct quenching treatment to obtain trans - 2 - substituted cyclohexyl three fluoro potassium borate, the catechol borane to obtain the racemate product, [...] photoinitiators enantiomerically pure product. The method has low cost, convenient source of raw materials, the operation is simple, and has industrial amplifying of the prospect. (by machine translation)

Provided is a preparation method for methyl cyclopentene from methyl cyclopentadiene through continuous hydrogenation. The preparation method comprises steps: first, methyl cyclopentadiene, a solvent and hydrogen are mixed and subjected to a hydrogenation reaction through fixed bed catalyst bed layers continuously, the material weight ratio of methyl cyclopentadiene to the solvent is 1:(5-10), the mol ratio of methyl cyclopentadiene to hydrogen is 1: (2.0-4.0), and the catalyst employs Pd as an active component and has a content of 0.3-1.0wt%; second, the hydrogenation products are then subjected to removal of weight, removal of methyl cyclopentane and dehydrogenation to obtain methyl cyclopentene with a purity of being more than 99%, and the overall yield of methyl cyclopentene is more than 90%. The preparation method is advantageous in that the preparation method employs hydrogenation reaction by-product methyl cyclopentane as a reaction solvent, improves the separation and refining processes of methyl cyclopentene combined with hydrogenation product material composition, and ensures that the separation and refining processes of hydrogenation products are simplified and the yield of methyl cyclopentene is raised in the premise of good hydrogenation reaction effects.

The growth of nanocrystalline metal-organic frameworks (nMOFs) around metal nanocrystals (NCs) is useful in controlling the chemistry and metric of metal NCs. In this Letter, we show rare examples of nMOFs grown in monocrystalline form around metal NCs. Specifically, Pt NCs were subjected to reactions yielding Zr(IV) nMOFs [Zr6O4(OH)4(fumarate)6, MOF-801; Zr6O4(OH)4(BDC)6 (BDC = 1,4-benzenedicarboxylate), UiO-66; Zr6O4(OH)4(BPDC)6 (BPDC = 4,4′-biphenyldicarboxylate), UiO-67] as a single crystal within which the Pt NCs are embedded. These constructs (Pt?nMOF)nanocrystal are found to be active in gas-phase hydrogenative conversion of methylcyclopentane (MCP) and give unusual product selectivity. The Pt?nUiO-66 shows selectivity to C6-cyclic hydrocarbons such as cyclohexane and benzene that takes place with 100 °C lower temperature than the standard reaction (Pt-on-SiO2). We observe a pore size effect in the nMOF series where the small pore of Pt?nMOF-801 does not produce the same products, while the larger pore Pt?nUiO-67 catalyst provides the same products but with different selectivity. The (Pt?nMOF)nanocrystal spent catalyst is found to maintain the original crystallinity, and be recyclable without any byproduct residues.

The effect of acidic properties of mesoporous zeolites on the control of product selectivity during the hydrogenative isomerization of methylcyclopentane has been investigated. A series of mesoporous zeolites with controlled acidic properties were prepared by postdealumination process with hydrochloric acid under hydrothermal conditions, and the resultant zeolites used for supporting colloidal Pt nanoparticles (NPs) with a mean size of 2.5 nm (±0.6 nm). As compared to the pure Pt NPs supported on catalytically inert mesoporous silica (MCF-17) as the reference catalyst that can produce isomers most selectively (～80%), the Pt NPs supported on mesoporous zeolites produced C6-cyclic hydrocarbons (i.e., cyclohexane and benzene) most dominantly. The type and strength of the Br?nsted (B) and Lewis (L) acid sites of those zeolites with a controlled Al amount are analyzed by using FT-IR after the adsorption of pyridine and NH3 temperature-programmed desorption measurements, and they are correlated with the selectivity change between cyclohexane and benzene. From this investigation, we found a linear relationship between the number of Br?nsted acid sites and the formation rate for cyclohexane. In addition, we revealed that more Lewis acidic zeolite having relatively smaller B/L ratio is effective for the cyclohexane formation, whereas more Br?nsted acidic zeolite having relatively larger B/L ratio is effective for the benzene formation.

Four kinds of novel lanthanocene complexes were synthesized in reasonable yield by the reaction of equimolar quantity of sodium salt of tridentate Schiff base [N-(2-methoxyphenyl)salicylideneimine] with indenyl lanthanoid dichloride tetrahydrofuranate in tetrahydrofuran. All the complexes after purification were characterized by MS and EA, respectively. These complexes isomerized successfully the 1,5- hexadiene into a mixture of products such as 1,4-hexadiene, 2,4-hexadiene,1,3-hexadiene, methylenecyclopentane and methylcyclopentene. Similarly they also proved effective for the polymerization of methylmethacrylate (MMA), 56.45 % yield and high molecular weight (355 × 103).

Process for the preparation of 1-methylcyclopentene by thermal reaction of cyclohexanol or cyclohexene or mixtures of both compounds to give 1-methylcyclopentene, wherein the resulting by-products 3-methylcyclopentene and 4-methylcyclopentene (double-bond isomers of 1-methylcyclopentene) are returned to the reaction.

Process for the preparation of cyclopentane derivatives of the formula I in which R is a C1- to C10-alkyl group, which comprises reacting cyclohexanol or cyclohexene or mixtures of both compounds to give 1-methyl-1-cyclopentene (1st stage) and subsequently adding a C1- to C10-alkanol onto the double bond of the 1-methyl-1-cyclopentene (2nd stage).

(Chemical Equation Presented) Novel insertion reactions of dichloro- and dibromocarbene into carbon-hydrogen bonds adjacent to cyclopropane rings are reported. It is found that the predominant isomers formed in the reactions with bicyclo[4.1.0]heptane result from insertion into the endo carbon-hydrogen bonds alpha to the three-membered ring. In the reactions of bicyclo[3.1.0]hexane, however, the exo dihalocarbene insertion products are formed as the major isomers. In some compounds cyclopropane rings "activate" adjacent carbon-hydrogen bonds, whereas other systems containing three-membered rings do not. Moreover, the influence of various substituents (methyl, geminal dimethyl, phenyl, methoxy, and ethoxy) attached to bicyclo-[3.1.0]hexane and bicyclo[4.1.0]heptane in dihalocarbene reactions has been studied. The findings can be explained by the concept of maximum orbital overlaps of Walsh orbitals of the cyclopropane rings and the α carbon-hydrogen bonds. In stark contrast, selective insertion into the tertiary carbon-hydrogen bonds of the cyclobutane ring in bicyclo[4.2.0]octane is observed.

Process for the alkylation of a cycloalkene, which process comprises alkylating a cycloalkene with an oxygenate under alkylating conditions in the presence of a zeolite; to yield an alkylated cycloalkene. Composition obtainable by such a process and use of such a composition as a gasoline blending component.

Polysulfone- and diphenyldisulfone-catalyzed alkene isomerizations are much faster for 2-alkyl-1-alkenes than for linear, terminal alkenes. The mechanism of these reactions has been investigated experimentally for the isomerization of methylidenecyclopentane into 1-methylcyclopentene, and theoretically [CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p) calculations] for the reactions of propene and 2-methylpropene with a methanesulfonyl radical, MeSO 2?. On heating, polysulfones and (PhSO2)2 equilibrate with sulfonyl radicals, RSO2?. The latter abstract allylic hydrogen atoms in one-step processes giving allylic radical/RSO 2H pairs that recombine within the solvent cage producing the corresponding isomerized alkene and RSO2?. The sulfinic acid, RSO2H, can diffuse out from the solvent cage (H/D exchange with MeOD,D2O) and reduce an allyl radical. Calculations did not support other possible mechanisms such as hydrogen exchange between alkenes, electron transfer, or addition/elimination process. Kinetic deuterium isotopic effects measured for the (PhSO2)2-catalyzed isomerization of methylidenecyclopentane and deuterated analogues and calculated for the H abstraction from 2-methylpropene and deuterated analogues by CH 3-SO2? are consistent also with the one-step hydrogen transfer mechanism. The high chemoselectivity for this reaction is not governed by an exothermicity difference but by a difference in ionization energies of the alkenes. Calculations for CH3SO2? + propene and CH3SO2? + 2-methylpropene show a charge transfer of 0.34 and 0.38 electron, respectively, from the alkenes to the sulfonyl radical in the transition states of these hydrogen abstractions.

Catalytic isomerization of 1,5-hexadiene by Cp2Ln Schiff base/NaH (Schiff base = C14H14NO2, Ln = Sm, Dy, Y, and Er) systems was studied. The isomerization resulted in a mixture of 1,4-hexadiene, 2,4-hexadiene, 1,3-hexadiene, methylene-cyclopentane, and methylcyclopentene. 1,4-Hexadiene and methylenecyclopentane were the intermediate products, while 2,4-hexadiene and methylcyclopentene were the end-products. The effects of the nature of catalyst, temperature, amount of the catalyst, time and solvent, on the isomerization rate and product composition were also studied. The ratio of the linear to the cyclic product in the reaction depended on the amount of catalyst used.

By reaction of phenoxyethanol with diverse structure acyl chlorides phenoxyethanol esters were synthesized containing in the molecule fragments of undecene acid and also of some ketocarboxylic acids. The latter acids were obtained by ozonation of alkylcyclenes. 2005 Pleiades Publishing, Inc.

A radical intermediate is generated when methylidenecyclopentane (1) is isomerized by SO2 into 1-methylcyclopentene (3) through the formation of a polysulfone polymer (PS), which first abstracts a hydrogen atom from the alkene. The allyl radical intermediate 2 abstracts a hydrogen atom from another alkene molecule 1, to yield the isomerized alkene and regenerating the allyl radical. Polysulfones are organic catalysts.

5- and 2-Methylbicyclo[2.2.1]hept-2-enes and 2-methylenebicyclo[2.2.1] heptane were synthesized by a new procedure, and their transformations in a flow system over stationary layer of aluminosilicate catalyst were studied at various temperatures. At 15-400°C these compounds undergo isomerization which is accompanied by δ-migration of hydrogen. The isomerization mechanism is discussed in terms of formation of classical carbocations, not invoking nonclassical carbenium ion.

Kinetics of heterolysis of 1-chloro-1-methylcyclopentane in MeOH, BuOH, cyclohexane, i-PrOH, t-BuOH, tert-C5H11OH, γ-butyrolactone, MeCN, PhCN, PhNO2, acetone, PhCOMe, cyclohexanone, and 1,2-dichloroethane at 25-50°C were studied by the verdazyl method. Correlation analysis of solvent effects on activation parameters of the reaction in 8 protic (additionally, AcOH and CF 3CH2OH) and 8 aprotic solvents together and separately in either group of solvents was performed. In all the solvents studied, two ΔH≠-ΔS≠ compensation effects were revealed.

By the synergistic catalysis of samarium ion and mercaptan, a series of 5-oxoalkanals was converted to (substituted) δ-lactones in efficient and stereoselective manners. This one-pot procedure comprises a sequence of acetalization, Tishchenko reaction and lactonization. The deliberative use of mercaptan, by comparison with alcohol, is advantageous to facilitate the catalytic cycle. The reaction mechanism and stereochemistry are proposed and supported by some experimental evidence. Such samarium ion/mercaptan cocatalyzed reactions show the feature of remote control, which is applicable to the asymmetric synthesis of optically active δ-lactones. This study also demonstrates the synthesis of two insect pheromones, (2S,5R)-2-methylhexanolide and (R)-hexadecanolide, as examples of a new protocol for asymmetric reduction of long-chain aliphatic ketones.

Investigation of cyclohexene conversion over Al-MCM-41 has shown that the concentrations of Bronsted and Lewis acid sites increase with the Al content of the materials. The conversion follows mainly two mechanisms: cyclohexene skeletal isomerisation (CSI) and hydrogen transfer (HT). The products with 6 carbon atoms in a molecule prevail in all cases. Some amounts of products with 1 to 8 carbon atoms are also formed as a result of cracking or alkylation. All these reactions can occur at the acidic centres of the catalysts. The process of conversion, proceeding over the Bronsted acid sites, results in the formation of coke deposits in addition to volatile products. The amount of coke decreases with increasing reaction temperature and decreasing Al content of the material. The deposits cause a decrease in the effective concentrations of both the Bronsted and Lewis acid sites. Thermodesorption of pyridine has shown that (i) the concentrations of the Bronsted and Lewis acid sites before and after the conversion processes differ only slightly and (ii) the acidic strength of the Bronsted sites is almost independent of their concentration and the Si/Al ratio.

The dehydrogenation of cyclohexene over carbon deposited on alumina, C/Al2O3, which was prepared by contacting hydrocarbons such as cyclohexane, cyclohexene, and cyclohexanone with alumina surface at ≥ 823 K, was studied under non-oxidative conditions. At 773 K, the conversion gradually decreased with process time, while the selectivity to the products slightly changed. Because the selectivity to dehydrogenated products such as benzene and 1,3-cyclohexadiene and their yields increased with increasing carbon content, the carbon deposited on alumina had dehydrogenation activity. The selectivities to the dehydrogenated products were maximized at a specific carbon content, while the selectivity to cyclohexane, hydrogenation product, increased with carbon content over the specific carbon content.

The kinetics of dehydrobromination of 1-bromo-1-methylcyclopentane in 10 protic and 31 aprotic solvents were studied by the verdazyl method: v = k[RBr], E1 mechanism. The reaction rate is determined mainly by the polarity and electrophilicity parameters of the solvent. The cohesion energy density, polarizability, and nucleophilicity of the medium weakly affect the reaction rate. The rate of heterolysis of 1-bromo-1-methylcyclopentane in polar solvents is 2 orders of magnitude higher than the rate of heterolysis of 1-bromo-1-methylcyclohexane; the rates of heterolysis of these substrates in weakly polar solvents are similar. The observed differences were ascribed to solvation effects caused by conformational transformations.

Hydrosilylation of 1-methylcyclopentene with chloromethylsilanes Me3-nSiHCln (n = 2, 3) yields dichloro(cyclopentylmethyl)methyl-and trichloro(cyclopentylmethyl)silanes, respectively. Chlorodimethylsilane (n = 1) adds to 1-methylcyclopentene to give a mixture of cis-and trans-chloro(methyl)(2-methylcyclopentyl)silanes, as well as chloro(cyclopentylmethyl)methylsilane. The hydrosilylation products were reacted with ethynylmagnesium bromide to prepare the corresponding ethynyl derivatives. Reaction of (cyclopentylmethyl)triethynylsilane with ethylmagnesium bromide and chlorotrimethylsilane gave (cyclopentylmethyl)tris(trimethylsilylethynyl)silane.

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Catalytic properties of ZrO2-SiO2 (14% molar) for cyclohexene conversion (skeletal isomerization and hydrogen transfer) have been studied. Textural and morphological properties were correlated to explain catalytic behavior. XRD, DTA-TGA, N2 adsorption, DRIFT, and acidity measurements by pyridine and dimethylpyridine chemisorption were used to characterize samples. The effect of the sulfation process upon surface structure as well on catalytic activity/selectivity has also been studied. It has been shown that catalytic activities are increased on sulfated samples, but at the same time products of the hydrogen transfer reaction seem to be increased too, lowering the selectivity of the reaction; isomerization always predominates. Sulfation transforms this compound to a relatively selective isomerization catalyst exhibiting greater catalytic activity.

Reaction of aminosulfur trifluorides with alcohols replaces the hydroxy group with fluorine.A study with the cyclic secondary alcohols trans-2-bromoindan-1-ol (3), trans-2-methylcyclopentanol (7), cis-2-methylcyclopentanol (8), trans-cyclopentanol (9), cis-cyclopentanol (10) and trans-2-fluorocyclopentanol (11) gave primarily inversion of configuration via an SN1-like pathway.The product stereochemistry and alkene formation in the reaction of aminosulfur trifluorides with cyclopentanols was similar to the products of solvolysis of cyclopentyl tosylates in methanol.The stereochemistry of the fluoro products was confirmed by independent synthesis or assigned by 1H and 19F NMR spectral data except for the deuteriated products 14 and 15 whose stereochemistry was assigned by their 2H NMR data.

Rate and equilibrium constants have been determined for both the aldol addition and the elimination steps in the intramolecular condensation reactions of 2,5-hexanedione, 2,6-heptanedione, 1-phenyl-1,5-hexanedione, and 5-oxohexanal. The overall thermodynamics are similar for cyclization of 2,5-hexanedione and 2,6-heptanedione; conversion of 2,5-hexanedione to the corresponding enone is actually more favorable, but the cyclization of 2,5-hexanedione is 2400 times slower than that of 2,6-heptanedione. As expected on the basis of intermolecular analogs, the addition step is less favorable and slower for 1-phenyl-1,5-hexanedione, and the addition step for 5-oxohexanal is more favorable though similar in rate to that for heptanedione. Detailed analysis of the kinetics and equilibrium for all of these compounds, as well as 2-(2-oxopropyl)benzaldehyde, in terms of Marcus theory, leads to the same intrinsic barriers for the intramolecular reactions as were seen previously for the intermolecular reactions. This means that rate constants for intramolecular aldol reactions should be predictable from the energetics of the reactions and that the effective molarity can be calculated. Methods for estimating thermodynamic quantities for reactants and products of these reactions have been examined.

Treatment of the parent and bridgehead-substituted 2,3-diazabicyclo[2.2.1]hept-2-enes (1a-d) and their bicyclo[2.1.0]pentanes (2a-d) with catalytic amounts (2-10 mol%) of tris(aryl)aminium hexachloroantimonates afforded the corresponding cyclopentenes (3a-d). A reversal in the regioselectivity of the 1,2 migration was observed for the unsymmetrical derivatives of bicyclo[2.1.0]pentane, namely 2b (methyl substitution) versus 2c (phenyl substitution). This surprising fact is rationalized in terms of delocalization of the positive charge into the aromatic ring for the 1,3-diyl radical cation, as corroborated by AM1 calculations.

Fluoride-modified (2.5 wt.percent F(1-)) AlPO4-Al2O3 (APAl-A; 5-25 wt.percent Al2O3) catalysts have been prepared and compared for their catalic activity/selectivity in cyclohexene conversion and cumene cracking.The characterization of catalysts modified with F(1-) was performed using X-ray diffraction (XRD), 27Al and 31P NMR and diffuse reflectance FTIR (DRIFT) spectrooscopies and N2 adsorption methods, and by the measurement of the surface acid character by chemisorption of pyridine (PY) and 2,6-dimethylpyridine (DMPY).Fluoride addition shifted the transition of AlPO4 from an amorphous to a crystalline (α-cristobalite) phase at a lower temperature.Fluoride-treated APAl-A catalysts contained both tetrahedral and octahedral aluminium (their ratio varied with anion type) while phosphorus always remained in P(OAl)4 environments.Moreover, two types of Al surface hydroxy groups at 3786 and 3738 cm-1, and only one type of P surface hydroxy group at 3670 cm-1, are found in the DRIFT spectra of the APAl-A catalysts.The DRIFT measurements also revealed that fluoride ion substitutes hydroxy groups on tetrahedrally coordinated Al and P centres in the surface.The PY and DMPY adsorption (pulse chemisorption and DRIFT spectroscopy) indicates that the addition of fluoride ion appreciably modifies the surface acidity of the AlPO4-Al2O3 catalyst by increasing the number and strength of Broensted acid sites.Furthermore, the addition of fluoride increases remarkably the activity for both processes and, for cyclohexene conversion, in contract to pure AlPO4-Al2O3 catalysts, where skeletal isomerization is the only catalysed reaction, bimolecular hydrogen transfer also takes place.The hydrogen transfer/skeletal isomerization ratio decreases as the Al2O3 loading increases although with all APAl-A-FM (fluoride-modified) catalysts the skeletal isomerization always predominates.The catalytic activities were correlated with both the acidity and the acid strength of the catalyst.Fluoride addition transformed a low activity cracking/dehydrogenation catalyst to one selective for cracking and exhibiting much greater catalytic activity.

The gas-phase pyrolysis, photoinduccd electron transfer (PET), and laser-jet 185-nm photochemistry of 2,3-diazabicyclo[2.2.1]hept-2-ene (1a), syn-7-methyl-2,3-diazabicyclo[2.2.1]hept-2-ene (syn-1b), anti-7-methyl-2,3-diazabicyclo[2.2.1]hept-2-ene (anti-1b), 1,4-dimethyl-2,3-diazabicyclo[2.2.1]hept-2-ene (1c), 7,7-dimethyl-2,3-diazabicyclo[2.2.1]hept-2-ene (1d), syn-7-(1-methylethyl)-2,3-diazabicyclo[2.2.2]hept-2-ene (syn-1e) were investigated and the results of their product studies compared with one another. Pyrolysis and conventional direct and benzophenone-sensitized 350-nm photolysis of the azoalkanes 1 yielded the bicyclo[2.1.0]pentanes 2 and negligible amounts of cyclopentenes 3. PET and benzophenone-sensitized laser-jet and 185-nm photolysis of the azoalkanes 1 led to significant quantities of cyclopentene derivatives 3, a bekavior that is attributed to radical cation-type 1,3-cyclopentadiyl intermediates, which subsequently suffer hydrogen or alkyl migration. The polar character of the radial cation D?+ is clearly demonstrated by the Wagner-Meerwein rearrangement into 2,3-dimethylcyclopentene (3′d) in the PET and 185-nm photolysis of azoalkane 1d. When the corresponding 1,3-cyclopentadiyl D?? was generated in the pyrolysis of 5,5-dimethylbicyclo[2.1.0]pentane (2d), the 3,3-dimethyl-1,4-pentadiene (4d) was obtained as the exclusive reaction product; instead of methyl migration, fragmentation into the 1,4-diene took place. The PET chemistry of the stereochemically labeled azoalkanes syn- and anti-1b revealed that the radical cations D?+ have a puckered geometry, because a stereochemical memory effect was observed for the cyclopentene products 3. Specifically, the pseudoaxial substituent at the stereolabled center migrates with preference, which speaks for a coplanar arrangement for the rearrangement in D?+. The common and distinct mechanistic features of the denitrogenation process of the various thermal and photochemical activation modes will be discussed.

Studies of the photosensitized electron transfer (PET) reactions of anti/syn-5-methylbicyclo[2.1.0]pentane (1a,b) and syn/anti-7-methyl-2,3-diazabicyclo[2.2.1]hept-2-ene (2a,b) have revealed a remarkable stereochemical memory effect. Thus, 1a and 2a furnished only 1-methylcyclopentene (3a) as the rearrangement product, while their isomers 1b and 2b afforded predominantly 3-methylcyclopentene (3b). The pathway responsible for the stereoselective olefin formation can be assigned to a radical cation rearrangement. This was established on the basis of direct ESR evidence showing that the 1,3-diyl radical cations 1a,b?+ detected initially at 80-90 K following the radiolytic oxidation of 1a,b in CF3CCl3 rearranged stereoselectively into the olefin radical cations 3a,b?+ at 105 K. The ESR results further establish that, in the puckered conformations of 1a,b?+, the pseudo-axial substituent on the methylene bridge is in almost perfect coplanar alignment with the radical cation 2p orbital lobes, thus facilitating its stereoselective migration. Also, in agreement with PET results, matrix ESR studies demonstrated that, on radiolytic oxidation of the azoalkanes 2a,b, the olefin radical cations 3a,b?+ were formed with high selectivity, although no precursor radical cations were detected in this case.

The role of successive 1,2-hydride shifts in the isomerization processes of cycloalkylcarbonium ions was demonstrated for the case of the alkylation of isomeric methylcyclopentanols or methylcyclopentenes in the presence of sulfuric acid and the isomerization of cyclohexene at acidic aluminum oxide.

The thermal cycloisomerization of some alkylacetylenes was investigated in a tubular quartz reactor.At 570 deg C 1-hexyne (1) rearranges to 3-methyl-1-cyclopentene (5) with a selectivity of about 27 by a reaction sequence including an acetylene-vinylidene rearrangement and 1,5-C,H insertion of the intermediately formed alkylidenecarbene species. 5-methyl-1-hexyne (2) behaves analogously forming 3,3-dimethyl-1-cyclopentene (6), while 2-hexyne (3) provides 1-methyl-1-cyclopentene (7) indicating that the acetylene-vinylidene rearrangement is obviuosly not restricted to 1,2-H shifts.The mechanism of the cycloisomerization of alkylacetylenes is investigated by means of D-labeled parent alkynes.The results show that the unimolecular cycloisomerization via alkylidenecarbenes obviously can be an important channel despite the dominance of a radical chain course. - Keywords: Alkyne/ Carbene/ Cycloisomerization/ Pyrolysis

Two series of AlPO4/TiO2 (APTi) catalysts containing different weight compositions have been prepared by the precipitation of AlPO4 (Al/P = 1) on commercial TiO2 (> 99.9 percent Anatase, Aldrich) using ammonia (APTi-A series) or ethene oxide (APTi-E series) as the precipitation agents.Physicochemical characterization of these catalysts was carried our by nitrogen adsorption, TG, X. r. d.., i. r. spectroscopy and surface acid measurements.The surface area, pore volume, crystal structure and surface-acid character were found to be dependent on the precipitation agent, chemical composition and calcination temperature.Changes in surface-acid character were determined by application of a dynamic method that consists in determining both the AlPO4/TiO2's catalytic activity and selectivity in cyclohexene skeletal isomerization using the Bassett-Habgood kinetic model for first-order processes.X-ray diffraction studies show that the incorporated AlPO4 inhibits the polymorphic anatase-rutile transformation in the calcination process of the APTi-A system.Also, APTi-A systems are less affected by thermal treatment than APTi-E ones.It was found that both the apparent rate constant and the selectivity are dependent on the calcination temperature although the most important influence is that of catalyst composition i. e. the AlPO4/TiO2 weight ratio.Thus, a decrease in catalytic activity is observed when TiO2 content increases.Selectivity studies carried out by the OPE curves and the Wheeler criterion show that isomerization products, 1- and 3-methylcyclopentene, are competitive stable primary reaction products coming from cyclohexene across a parallel reaction network.

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On a ultrastabilized protonic Y zeolite (USHY) cyclohexene undergoes various reactions: isomerization into methylcyclopentenes, hydrogen transfer, cracking and formation of carbonaceous deposits ("coke").The transfer of hydrogen which comes either from cyclohexene (with formulation of benzene) or from heavy carbonaceous compounds causes the saturation of cyclohexene and of methylcyclopentenes.While the total transformation rate increases when the temperature increases, the rate of coke formation decreases slightly.This abnormal effect can be due to a modification in the composition of heavy carbonaceous compounds held back in the zeolite pores.The relative significance of various reactions depends very much on the temperature: at 120 deg C "coke" formation is faster than isomerization and much faster than hydrogen transfer, the hydrogen implicated coming from heavy carbonaceous compounds only.From 200 deg C upwards, isomerization and hydrogen transfer become the main reactions.Even if the production of benzene increases significantly with the temperature, hydrogen always comes mainly from the heavy carbonaceous compounds and is transfered faster to methylcyclopentenes than to cyclohexene.Light compounds resulting from the cracking of methylcyclopentenes appear above 350 deg C.The formation of all the products can be explained by mechanisms in which carbenium ion intermediates intervene.

Acidic and catalytic properties of alumina containing amall amounts of Ti(IV) and Na(I) (up to 1 wt.percent of both) were examined.It has been proved that the amount of acid sites with the strength H0 /= 3.3 and the initial reaction rates of cyclohexene isomerisation depend linearly on calculated total electronegativity of the corresponding mixture of oxides.

Two series of acyclic terminal vinyl bromides (1...4 and 5...7) were tested in the reaction with potassium tert-butoxide as precursors of alkylidene carbenes.As expected 1 up to 4 only give 1-alkynes whereas the 2-methylated vinyl bromides 5, 6 and 7 yield 1-methylated cyclopentenes predominantly besides 2-alkynes.The formation of cyclopentenes indicates a reaction route via alkylidene carbenes and 1,5-C-H-insertion reactions, that of 2-alkynes is convincing evidence for 1,2-alkyl shift reactions in 2-methyl substituted alkylidene carbenes.The selectivity of 1,5-C-H-insertion depends on the degree of alkyl substitution of the C-5-atom.At 240 deg C the selectivity is 1deg:2deg:3deg ca. 1:54:240.

The effectiveness of copper(II) triflate (copper(II) trifluoromethanesulfonate) as a new dehydrating reagent for a variety of alcohols has been demonstrated.Based on several control experiments, a possible mechanism is suggested.

Experimental results are presented for deprotonation of 1-methylcyclopentyl cation (1) by ammonia, trimethylamine, and 1-methylcyclopentylamine at pressures below 10-3 Torr, which yields two neutral products, 1-methylcyclopentene (2) and methylenecyclopentane (3).The isomer ratio varies from 2:3 = 2.74 for trimethylamine, consistent with previous reports.FTMS measurement of ion-molecule reaction rates of 1 plus ammonia gives an efficiency of 0.34 when 1 is generated by a 20-70 eV electron impact on bromocyclohexane.REaction of the predeuterated cation 1-d11 with ammonia yields products that reveal only a very low level of hydrogen scrambling between acid and base.Isotope effects on the reaction rate and the neutral product ratio, determined from experiments using 1-d11 or ND3, are found to be small.Two mechanistic alternatives are discussed: Lewis (in which covalent acid-base complexes are formed) and Eigen (in which hydrogen-bonded intermediates are formed).Reaction of 1-d11 with 1-methylcyclopentylamine shows only a small amount of interchange of deuterated and undeuterated alkyl groups, which argues against a Lewis mechanism as an obligatory pathway.Experimental results are interpreted in terms of orbiting intermediates, in which acidic C-H bonds and the basic nitrogen experience large deviations from collinearity.More than one subsequent step is required for the reactants to engage chemically.In order for Eigen mechanisms to operate, a C-H bond must point toward the nitrogen, which requires loss of some internal degrees of freedom.For proton transfer to be completed, the nitrogen lone pair must be pointed along the C-H...N axis, which requires loss of additional degrees of freedom.Progress of the reaction beyond the initially formed orbiting intermediate is described by a scheme in which these stages of approach to reactive orientaion represent discrete steps.

The regioselectivity of the addition of molecular bromine chloride to alkenes is dependent on both the steric and electronic effects of the alkyl substituent.In contrast, the regioselectivity of the addition of dichlorobromate (1-) ion to alkenes is controlled mainly by the steric effect of the substituent.

The intramolecular cyclopentene annulation methodology which combines the cyclopropanation of dienic diazoketones and the vinylcyclopropane rearrangement is utilized to synthesize linear tricyclopentanoids of the hirsutane class or nonlinear members of the isocomene class.The requisite diene precursors, endocyclic or exocyclic, respectively, are obtained from acylcyclopentenes via orthoester Claisen rearrangement of either allyl or propargyl alcohols.The scope and the generality of the method are indicated and experimental details are presented pertaining to thesynthesis of precursory dienes for hirsutane and isocomene sesquiterpenes.Full details are disclosed concerning the total synthesis of epiisocomene and the synthesis of linearly fused precursors to coriolin sesquiterpenes.

A modification of the high temperature - dilute acid (HTDA) method for deuterium labelling of aromatic compounds has been applied to the H-D exchange of a number of cyclic and acyclic alkenes.Cyclopentene, cyclohexene, cyclododecene, and tetramethylethylene have been completely exchanged in excellent yield. 1-Methylcyclopentene and 1-methylcyclohexene have also been perdeuterated and cycloheptene and cyclooctene partially labelled but require spinning band distillation or preparative glpc for separation from rearrangement products.A variety of C5-C8 acyclic alkeneshave also been treated under HTDA conditions.

The kinetics of oxidative cleavage of glycols by obalt(III) acetate in acetic acid have been studied.The substrates examined include cis- and trans-cyclopentane- and cyclohexane-1,2-diols and their mono- and dimethyl derivatives.The rates were first-order in both cobalt(III)acetate and substrate in all cases.In the oxidation of five-membered ring diols, cis-diols were generally oxidized faster than the trans-isomers.Complex results were obtained in the case of six-membered ring diols.Thermodynamic parameters were calculated for all the substrates.A mechanism involving a bidente complex of cobalt(III) acetate dimer and glycol is sugge sted, except for the case of trans-cyclopentane-1,2-diols, for which a monodentate intermediate is proposed.

The acetolysis of a series of bicycloalkanes and propellanes has been studied.The effect of ring strain, caused by changing ring size or introducing a trans-ring fusion, on the rate and products of the reaction has been examined.No correlation was found between rates of acetolysis and strain energy relief, but with the exception of propellane, there is a rough correlation with ionization potentials.The degree of polarization of the C-C bonds in the presence of a proton correlates very well with reactivity and is a controlling factor for the acetolysis rates.The importance of the energies of unoccupied orbitals with the appropriate symmetry in controlling electron polarization is shown by the large difference in rate of reaction between - and propellanes.

Direct irradiations at 185 nm of 1-octene and 2-methyl-1-pentene in pentane gave alkylidene carbenes through the molecular elimination of terminal hydrogens, as well as double-bond migration products via 1,3-shift of allylic hydrogen and radical-derived products.

(-)-(S)- and (+)-(R)-3-methylcyclopentene (1) has been prepared in a stereochemically unambiguous synthesis.The (S)-configuration for (-)-1 was confirmed by correlation with (-)-(S)-1-methylindane.

The intramolecular alkylation of several bromo- and epoxy-2-methylcyclopentenones, 18-23 and 33, are described.In all cases, except 33, alkylative cyclization occours at the γ' position to the conjoint ring systems 25-31.The "blocked" bromide 33 (γ' geminal dimethyl substituent) cyclizes to the fused ring hydrindenones 35 and/or 34 depending upon conditions.Enolate anion generation from 3-ethyl-2-methyl-2-cyclopentenone (36) with various bases (KH, LDA, Et3N) is described and the anion populations determined by quenching with chlorotrimethylsilane to afford the enol ethers 39-41.The intramolecular alkylations are discussed.

Cyclohexene skeletal isomerization, in a microcatalytic pulse reactor, was investigated using Al2O3 and AlPO4-Al2O3 as catalysts.Apparent rate constants and apparent activation energies were calculated according to the kinetic model of Bassett-Habgood.Selectivity studies cuncluded that 1-MCP and 3-MCP were competitive products with a first-order kinetics.The rate constants as well as the selectivity at 1-MCP increase with an increase in the number and strength of stronger acid sites, measured by means of the irreversible adsorption of aniline in cyclohexane, at 298 K, using a spectrophotometric method.The parallel reaction pathway, proposed for AlPO4 catalysts, agrees with both the observed rates and selectivities using Al2O3 and AlPO4-Al2O3 catalysts.