1191-96-4Relevant articles and documents
Liquid-phase noncatalytic butene oxidation with nitrous oxide
Semikolenov,Dubkov,Starokon',Babushkin,Panov
, p. 948 - 956 (2005)
The kinetics and mechanism of noncatalytic liquid-phase oxidation of but-1-ene and but-2-ene with nitrous oxide in a benzene solution in the temperature range from 180 to 240°C were studied. Oxidation proceeds via the 1,3-dipolar cycloaddition mechanism to form carbonyl compounds. Both of these reactions occur with close rates and activation energies and have the first orders with respect to the alkene and N2O. A considerable fraction (39%) of but-1-ene involved in oxidation undergoes cleavage at the double bond yielding propanal and an equivalent amount of methylene, the latter producing ethylcyclopropane and cycloheptatriene. The oxidation of but-2-ene proceeds with a minimum bond cleavage and affords methyl ethyl ketone with 84% selectivity. Regularities of the oxidation of terminal and internal alkenes C 2-C8 with nitrous oxide were analyzed using the previously published data.
Light-Promoted Transfer of an Iridium Hydride in Alkyl Ether Cleavage
Fast, Caleb D.,Schley, Nathan D.
supporting information, p. 3291 - 3297 (2021/10/12)
A catalytic, light-promoted hydrosilylative cleavage reaction of alkyl ethers is reported. Initial studies are consistent with a mechanism involving heterolytic silane activation followed by delivery of a photohydride equivalent to a silyloxonium ion generated in situ. The catalyst resting state is a mixture of Cp*Ir(ppy)H (ppy = 2-phenylpyridine-κC,N) and a related hydride-bridged dimer. Trends in selectivity in substrate reduction are consistent with nonradical mechanisms for C-O bond scission. Irradiation of Cp*Ir(ppy)H with blue light is found to increase the rate of hydride delivery to an oxonium ion in a stoichiometric test. A comparable rate enhancement is found in carbonyl hydrosilylation catalysis, which operates through a related mechanism also involving Cp*Ir(ppy)H as the resting state.
Cross-Linked "poisonous" Polymer: Thermochemically Stable Catalyst Support for Tuning Chemoselectivity
Yun, Seongho,Lee, Songhyun,Yook, Sunwoo,Patel, Hasmukh A.,Yavuz, Cafer T.,Choi, Minkee
, p. 2435 - 2442 (2016/04/26)
Designed catalyst poisons can be deliberately added in various reactions for tuning chemoselectivity. In general, the poisons are "transient" selectivity modifiers that are readily leached out during reactions and thus should be continuously fed to maintain the selectivity. In this work, we supported Pd catalysts on a thermochemically stable cross-linked polymer containing diphenyl sulfide linkages, which can simultaneously act as a catalyst support and a "permanent" selectivity modifier. The entire surfaces of the Pd clusters were ligated (or poisoned) by sulfide groups of the polymer support. The sulfide groups capping the Pd surface behaved like a "molecular gate" that enabled exceptionally discriminative adsorption of alkynes over alkenes. H2/D2 isotope exchange revealed that the capped Pd surface alone is inactive for H2 (or D2) dissociation, but in the presence of coflowing acetylene (alkyne), it becomes active for H2 dissociation as well as acetylene hydrogenation. The results indicated that acetylene adsorbs on the Pd surface and enables cooperative adsorption of H2. In contrast, ethylene (alkene) did not facilitate H2-D2 exchange, and hydrogenation of ethylene was not observed. The results indicated that alkynes can induce decapping of the sulfide groups from the Pd surface, while alkenes with weaker adsorption strength cannot. The discriminative adsorption of alkynes over alkenes led to highly chemoselective hydrogenation of various alkynes to alkenes with minimal overhydrogenation and the conversion of side functional groups. The catalytic functions can be retained over a long reaction period due to the high thermochemical stability of the polymer.
A Photochemical Source of Real Alkylcarbenes
Glick, HC,Likhotvorik, Igor R.,Jones, Maitland
, p. 5715 - 5718 (2007/10/02)
Treatment of 7,7-dibromodibenzobicycloheptane with di-tert-butylcuprate or dibutylcuprate, followed by quenching with water, led to exo- and endo-7-monoalkyldibenzobicycloheptanes.Photolysis through either quartz or Pyrex gave the products of intramolecular reactions of the corresponding alkylcarbenes.The temperature dependence of the products formed from tert-butylcarbene was verified, and butylcarbene was trapped intermolecularly. - Keywords: carbenes, retrocycloadditions, insertion reactions.
GC/MS SEPARATION AND IDENTIFICATION OF THE C5H10 ISOMERS. APPLICATION TO THE Hg 6(3P1) PHOTOSENSITIZED REACTIONS OF cis-2-PENTENE, 1-PENTENE AND trans-1,2-DIMETHYLCYCLOPROPANE
Mare, George R. De,Termonia, Marc
, p. 155 - 160 (2007/10/02)
The analysis (separation and identification) of eleven C5H10 isomers is performed using coupled GC/MS with a 70 m glass capillary column containing a 2.5 μm thick film of PS225 as stationary phase.Cryogenic CO2 cooling improves the separations.The total analysis time is less than 12 minutes. - Some mechanistic details on the Hg 6(3P1) (hereafter denoted by Hg*) photosensitization of the title compounds are elucidated.Thus the Hg* photosensitization of cis-2-pentene at 20 Torr yields methylcyclobutane with a quantum yield Φ = O.1, not ethylcyclpropane as was previously thought. (Ethylcyclopropane is formed in trace quantities.) The photostationary state for the Hg* sensitization of the 2-pentenes is confirmed to correspond to the concentration ratio / = 1.00.Trans-1,2-dimethylcyclopropane is a product of the Hg* photosensitization of 1-pentene.The major products of the Hg* photosensitization of trans-1,2-dimethylcyclopropane at 80 Torr are 3-methyl-1-butene, trans- and cis-2-pentene and cis-1,2-dimethylcyclopropane which are all formed with quantum yields near 0.1 and in the ratios 1.04 : 1.07 : 1.00 : 1.45.
A Mechanistic Study of the Rhodium-Catalyzed Cyclization of 4-Hexenals. Reactions of Deuterio-4-hexenals
Campbell, Richard E.,Lochow, Charles F.,Vora, Krishnakant P.,Miller, Roy G.
, p. 5824 - 5830 (2007/10/02)
In independent experiments, four carbons in the 4-pentenal skeleton have been labeled with deuterium or methyl and the fate of each label has been determined as the pentenal was transformed into a cyclopentanone derivative by RhCl(PPh3)3 (1) at 24-26 deg C.The catalyst converted 4-hexenal to 2-methylcyclopentanone (2) in CHCl3 and C6H6.Approximately equivalent amounts of hydrocarbon decarbonylation products and RhCl(CO)(PPh3)2 were also formed. 3-Methyl-4-pentenal was isomerized to 3-methylcyclopentanone by 1. 4-Hexenal possessing deuterium at C-2 was isomerized to 2 which contained deuterium at C-5. trans-4-Hexenal-1-d was cyclized to 2-3-d and 2-2-d in 9:1 ratio when the reaction was carried to a low conversion.The deuterium in the 2-3-d product was found to be cis to the C-2 CH3 group. cis-4-Hexenal-1-d was isomerized by 1 to afford 2-3-d possessing deuterium trans to the C-2 CH3 group.NMR analyses of these products were assisted by the synthesis and characterization of 2-cis-2,3-d2 by treatment of 2-methylcyclopent-2-en-1-one with D2 and 1.The 2-cis-2,3-d2 could be converted to a 1:1 mixture of 2-3-d diastereomers on treatment with HCl in MeOH/H2O.The result demonstrated that the cyclization of 4-hexenal-1-d occurred by a syn addition of the C-D bond to the olefinic bond to generate 2-3-d.The presence of C2H4 in reactin mixtures of 1 and 4-hexenal-1-d resulted in the formation of substantial 2-d0 and C2H3D.The deuterium locations in the 1-pentene, 2-pentene, and ethylcyclopropane decarbonylation products derived from reaction of 4-hexenal-1-d with 1 were determined.The results were interpreted in terms of a hydroacylation mechanism involving an acylrhodium(III) hydride complex and organometallic intermediates derived therefrom.The hydroacylation and decarbonylation products appear to be generated via common intermediates.
Ring-opening of Some Radicals containing the Cyclopropylmethyl System
Beckwith, Athelstan L. J.,Moad, Graeme
, p. 1473 - 1482 (2007/10/02)
Mono- and bi-cyclic radicals containing the cyclopropylmethyl system are readily generated by interaction of the appropriate halides with triphenyl- or tributyl-stannane.Each radical studied underwent ring-opening by fission of the more substituted βγ-bond.In the case of the secondary radical (12b) the new double bond was formed preferentially in the trans-configuration.Rate constants, which cannot be determined with high accuracy by this method, lie in the range 1E7-3E8 s-1 at 25 deg C.When generated by the flow method in the e.s.r. cavity α-hydroxycyclopropylmethyl radicals undergo β-fission followed by 1,5-hydrogen atom t ransfer to afford enoxyl radicals.The latter reaction occurs more slowly in water than in non-polar solvents.The rigid hydroxynortricyclyl (43) undergoes preferential fission of the less substituted βγ-bond, possibly because of the dipolar nature of the transition state.
