4016-15-3Relevant academic research and scientific papers
Structure elucidation and synthesis of dioxolanes emitted by two triatoma species (Hemiptera: Reduviidae)
Bohman,Troeger,Franke,Lorenzo,Francke,Unelius
experimental part, p. 690 - 694 (2011/07/07)
Volatiles from the metasternal glands of two species of true bugs of the Triatominae subfamily, Triatoma brasiliensis and Triatoma infestans, were analyzed by SPME-GC/MS. Two sets of new natural products were found: (4S,5S)- and (4R,5R)-2,2,4-triethyl-5-methyl-1,3-dioxolane (1) (major component) and (4S*,5S*)-2,4-diethyl-2,5-dimethyl-1,3-dioxolane (2) (trace component), (2R/S,4S,5S)- as well as (2R/S,4R,5R)-4-ethyl-5-methyl-2-(1- methylethyl)-1,3-dioxolane (3) (minor component), (2R/S,4S*,5S*)-4- ethyl-5-methyl-2-(1-methylpropyl)-1,3-dioxolane (4) (trace component), and (2R/S,4S*,5S*)-4-ethyl-5-methyl-2-(2-methylpropyl)-1,3-dioxolane (5) (trace component). Syntheses of optically active 1 and 3 were carried out by reacting pure enantiomers of 2,3-pentanediol with 3-pentanone or 2-methylpropanal. The preparation of pure stereoisomers of 2,3-pentanediol involved a novel key step for the synthesis of secondary alcohols: the reduction of a carboxylic ester by means of DIBAH and in situ alkylation of the intermediate by Grignard reaction at low temperature. Starting from the pure enantiomers of methyl lactate, all four stereoisomers of 2,3-pentanediol were synthesized and transformed to the corresponding isomers of 1 and 2. Relative configurations of the natural products and enantiomeric compositions of naturally occurring 1 and 2 were determined by comparison of their mass spectra and gas chromatographic retention times (co-injection) with those of authentic reference samples.
(4 S,5 S)-2,2,4-Triethyl-5-methyl-1,3-dioxolane: A new volatile released by a triatomine bug
Unelius,Bohman,Lorenzo,Troeger,Franke,Francke
supporting information; experimental part, p. 5601 - 5603 (2011/03/20)
Adults of the triatomine bug Triatoma brasiliensis release 2,2,4-triethyl-5-methyl-1,3-dioxolane (1) as a mixture of the (4S,5S)- and (4R,5R)-enantiomers in a ratio of 4:1. Among the volatile acetals identified from insects so far, this is the first example resulting from an intermolecular condensation of a carbonyl moiety and a diol substructure.
Catalytic epoxidation of olefins in the presence of a vanadyl porphyrin complex
Miralamov,Mamedov
, p. 25 - 27 (2007/10/03)
It was found that vanadyl porphyrin complexes synthesized from petroleum metal porphyrin concentrates stimulated epoxidation during the olefin oxygenation process. The yields of obtained oxiranes turned out to be 38-75%, depending on the olefin structure. An epoxidation mechanism that suggests the formation of a protonated dioxygen adduct as an intermediate during oxygenation of olefins in the presence of vanadyl porphyrin complexes was proposed. An analogy is drawn between the epoxide formation reaction upon the catalytic oxygenation of olefins and the Prilezhaev reaction. MAIK "Nauka/Interperiodica".
Is a Linear Relationship between the Free Energies of Activation and One-Electron Oxidation Potential Evidence for One-Electron Transfer Being Rate Determining? Intermediates in the Epoxidation of Alkenes by Cytochrome P-450 Models. 4. Epoxidation of a Series of Alkenes by Oxo(meso-te...
Garrison, J. Mark,Ostovic, Drazen,Bruice, Thomas C.
, p. 4960 - 4966 (2007/10/02)
The mechanism of reaction of (porphyrin)CrV(O)(X) with alkenes has been investigated by combining the electrochemical determinations of redox potentials with the tools of kinetics and product identification.Studies include the following: (i) the dynamics of the reaction of oxo(meso-tetrakis(2,6-dibromophenyl)porphinato)chromium(V) ((Br8TPP)CrV(O)(X) with 16 alkenes (1,4-diphenyl-1,3-butadiene, 4-methoxystyrene, 1,1-diphenylethylene, 4-methylstyrene, 2,3-dimethyl-2-butene, cis-stilbene, styrene, 4-acetoxystyrene, cyclohexene, norbornene, cis-cyclooctene, 4-cyanostyrene, cis-2-pentene, cyclopentene, 1-hexene, 1-octene); (ii) the dynamics of the reaction of norbornene with five (porphyrin)CrV(O)(X) species (oxo(meso-tetraphenylporphinato)chromium(V), oxo(meso-tetrakis(2,4,6-trimethylphenyl)porphinato)chromium(V), oxo(meso-tetrakis(2,6-dichlorophenyl)porphinato)chromium(V), oxo(meso-tetrakis(2,6-difluorophenyl)porphinato)chromium(V), and oxo(meso-tetrakis(2,6-dibromophenyl)porphinato)chromium(V)).Alkenes were selected on the basis of their 1e oxidation potential so as to cover the widest range of E1/2 possible (1.14-2.80 V (SCE)), and the 1e oxidation potentials for the (porphyrin)CrV(O)(X) varied from 0.790 to 0.975 V (SCE).Standard solutions of (porphyrin)CrV(O)(X) were obtained by controlled-potential bulk electrolysis of the corresponding (porphyrin)CrIV(O) and used in the kinetic (CH2Cl2 solvent, 30 deg C) and product studies.The time course for the change in concentration of (Br8TPP)CrV(O)(X), (Br8TPP)CrIV(O), and (Br8TPP)CrIII(X) was simulated for the reaction of (Br8TPP)CrV(O)(X) with selected alkenes possessing "low, medium, and high" oxidation potentials.The time dependence of V(O)(X)>, IV(O)>, and III(X)> as well as the could be accurately fit to a scheme involving the following: (i) bimolecular reaction of alkene with (Br8TPP)CrV(O)(X) to provide alkene oxidation product + (Br8TPP)CrIII(X); (ii) reversible comproportionation of (Br8TPP)CrV(O)(X) + (Br8TPP)CrIII(X) to provide (Br8TPP)CrIV(O) + (Br8TPP)CrIV(X)2; (iii) a spontaneous reversion (due to oxidation of solvent or solutes) of (Br8TPP)CrV(O)(X) to (Br8TPP)CrIV(O).The remainder of the alkene oxidations were followed by the more simplistic procedure of following disappearance of (Br8TPP)CrV(O)(X).The second-order rate constants (k1) determined by either method were found to be in agreement.For about half the alkenes studied, the standard free energies for 1e oxidation by (Br8TPP)CrV(O)(X), to provide alkene-derived ? cation radicals (calculated from the potentials for 1e reduction of (Br8TPP)CrV(O)(X) and 1e oxidation of the alkenes to ? cation radicals), exceed the free energies of activation for epoxidation of alkenes by (Br8TPP)CrV(O)(X).A unified mechanism ...
Dissociation of Positively Charged Aliphatic Epoxides. II. +. Epoxides and α,β Unsaturated Ethers
Bouchoux, Guy,Djazi, Feycal,Hoppilliard, Yannik,Jaudon, Pascale,Nouts, Nathalie
, p. 33 - 41 (2007/10/02)
The unimolecular dissociations of C5 epoxides ions mono- or disubstituted at C1 give exclusive loss of CH3 and exclusive formation of methoxyvinyl carbenium ion, both in the source and in the 2nd field-free region.In the case of the 1,2-disubstituted ion in the 2nd field-free region the loss of ethene is the only pathway, while a competition occurs for the trisubstituted ion leading to +. and +. ions, the structure of which are demonstrated.The first step of the different mechanisms is the cleavage of the heterocyclic C-C bond.
USING THE COMPARISON OF STERIC VERSUS ELECTRONIC EFFECTS TO INFER MECHANISTIC INFORMATION IN STEPWISE ELECTROPHILIC ADDITION REACTIONS INVOLVING THREE-MEMBERED CYCLIC INTERMEDIATES
Nelson, Donna J.,Soundararajan, Raman
, p. 6207 - 6210 (2007/10/02)
Correlations of IP's versus relative reactivities or formation constants of reactions of alkenes with ArSCl, MeCO3H, Ag(1+), or HgCl2 reveal that complexation reactions show steric dependence, that additions with the first step rate-determining are sterically independent, and that those with the second step rate-determining are sterically dependent.
The Mechanism of Ozone-Alkene Reactions in the Gas Phase. A Mass Spectrometric Study of the Reactions of Eight Linear and Branched-Chain Alkenes
Martinez, Richard I.,Herron, John T.,Huie, Robert E.
, p. 3807 - 3820 (2007/10/02)
The stable products of the low-pressure (4 - 8 torr (1 torr = 133.33 Pa)) gas-phase reactions of ozone with ethene, propene, 2-methylpropene, cis-2-butene, trans-2-butene, trans-2-pentene, 2,3-dimethyl-2-butene, and 2-ethyl-1-butene have been identified by using a photoionization mass spectrometer coupled to a stirred-flow reactor.The products observed are characteristic of (i) a primary Criegee split to an oxoalkane (aldehyde or ketone) and a Criegee intermediate, (ii) reactions of the Criegee intermediates such as unimolecular decomposition, secondary ozonide formation, etc., and (iii) secondary alkene chemistry involving OH and other free-radical products formed by the unimolecular decomposition of the Criegee intermediates.The secondary OH - alkene - O2 reactions account for a significant fraction of the alkene (CnH2n) consumed and lead to characteristic products such as Cn dioxoalkanes nH2n + 30)>, Cn acyloins nH2n + 32)>, and Cn alkanediols nH2n + 34)>.Cn oxoalkanes and Cn epoxyalkanes observed at m/e (CnH2n + 16) are probably formed primarily via epoxidation of the alkene by O3.A general mechanism has been proposed to account for the observations.
Process for preparing aldehydes from oxirane compounds
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, (2008/06/13)
Aldehydes are prepared by reacting an oxirane compound with hydrogen peroxide in the presence of a boron compound.
