6857-93-8Relevant academic research and scientific papers
Donor-Stabilized Silylene/Phosphine-Supported Carbon(0) Center with High Electron Density
Troadec, Thibault,Wasano, Tatsuya,Lenk, Romaric,Baceiredo, Antoine,Saffon-Merceron, Nathalie,Hashizume, Daisuke,Saito, Yosuke,Nakata, Norio,Branchadell, Vicen?,Kato, Tsuyoshi
, p. 6891 - 6895 (2017)
An isolable donor-stabilized silavinylidene phosphorane was synthesized. This molecule, which can also be regarded as a new carbon(0) complex featuring a phosphine and a donor-stabilized silylene ligand, presents a central carbon atom with a remarkably high electron density (?1.82). Furthermore, the experimental electron-density study of this compound demonstrates the delocalization of the σ-lone pair at the central carbon atom toward the silicon center, a feature which is remarkably different from electronic situation of other bent-allene-type molecules. This result clearly demonstrates the powerful electron-donating ability of donor-stabilized silylene ligands, as well as their excellent electron-acceptor properties.
Influence of the chemical structure on odor qualities and odor thresholds in homologous series of alka-1,5-dien-3-ones, alk-1-en-3-ones, alka-1,5-dien-3-ols, and alk-1-en-3-ols
Lorber, Katja,Schieberle, Peter,Buettner, Andrea
, p. 1025 - 1031 (2014/03/21)
Odor qualities and odor thresholds in air in homologous series of synthesized alk-1-en-3-ols and alka-1,5-dien-3-ols and their corresponding ketones were evaluated by gas chromatography-olfactometry. In the series of the alk-1-en-3-ols and alk-1-en-3-ones the odor quality changed successively from pungent for the compounds with five carbon atoms via metallic, vegetable-like for the six- and seven-carbon odorants to mushroom-like for the compounds with eight and nine carbon atoms. With further increase in chain length the mushroom-like impression decreased and changed to citrus-like, soapy, or herb-like. In both series, two odor threshold minima were found for the six-carbon and also for the eight- and nine-carbon odorants, respectively. In contrast to this, the odor qualities in the series of the (Z)- and (E)-alka-1,5-dien-3-ols and their corresponding ketones did not change significantly with geranium-like, metallic odors and an increasing mushroom-like odor note with increasing chain length. The lowest thresholds were found for the eight- and nine-carbon (Z)-compounds, respectively.
Influence of the chemical structure on odor qualities and odor thresholds in homologous series of alka-1,5-dien-3-ones, alk-1-en-3-ones, alka-1,5-dien-3-ols, and alk-1-en-3-ols
Lorber, Katja,Schieberle, Peter,Buettner, Andrea
, p. 1025 - 1031 (2015/04/22)
Odor qualities and odor thresholds in air in homologous series of synthesized alk-1-en-3-ols and alka-1,5-dien-3-ols and their corresponding ketones were evaluated by gas chromatography-olfactometry. In the series of the alk-1-en-3-ols and alk-1-en-3-ones the odor quality changed successively from pungent for the compounds with five carbon atoms via metallic, vegetable-like for the six- and seven-carbon odorants to mushroom-like for the compounds with eight and nine carbon atoms. With further increase in chain length the mushroom-like impression decreased and changed to citrus-like, soapy, or herb-like. In both series, two odor threshold minima were found for the six-carbon and also for the eight- and nine-carbon odorants, respectively. In contrast to this, the odor qualities in the series of the (Z)- and (E)-alka-1,5-dien-3-ols and their corresponding ketones did not change significantly with geranium-like, metallic odors and an increasing mushroom-like odor note with increasing chain length. The lowest thresholds were found for the eight- and nine-carbon (Z)-compounds, respectively.
Photochemistry of 1,5-hexadien-3-ones: Wavelength-dependent selectivity in intramolecular enone-olefin photoadditions
Dauben, William G.,Cogen, Jeffrey M.,Ganzer, George A.,Behar, Victor
, p. 5817 - 5824 (2007/10/02)
The photochemistry of ten 1,5-hexadien-3-ones in methanol is studied over the wavelength range of 313-366 nm, by using monochromatic light. With the goal of understanding the unusual wavelength-dependent selectivity observed for 5-methyl-1,5-hexadien-3-one (1), quantum yield measurements, structure reactivity studies, triplet sensitization, and quenching experiments are performed. While six of the ten dienones studied show selectivities that are independent of irradiation wavelength from 313 to 366 nm, four of the dienones exhibit wavelength-dependent selectivities that are similar to that observed in 1, thus establishing that 1 is not unique, as previously believed. Triplet sensitization studies suggest that the wavelength dependence results, largely, from a single-state α-cleavage reaction that competes with triplet cycloaddition. A variety of triplet quenchers were ineffective at inhibiting these reactions. Some possible mechanisms are discussed.
Rearrangement of Substituted Bicyclohex-2-yl Mesylates Under Solvolytic Conditions
Della, Ernest W.,Elsey, Gordon M.,Skouroumounis, George
, p. 1231 - 1244 (2007/10/02)
When heated in formic acid, methyl 2-mesyloxybicyclohexane-2-carboxylate (3) ionizes significantly faster than expected and yields the rearranged isomer (6) essentially quantitatively.The latter, on the other hand, solvolyses at a much reduced rate.These data are interpreted as evidnce for the presence in the ester of a favourable mesomeric interaction which largely offsets an otherwise destabillizing inductive effect when the ester is attached to a carbocationic centre.The corresponding cyano mesylates (8) and (29) were found to behave in an analogous manner when exposed to the solvolytic conditions.Heating the related acid mesylate (25) in an aqueous medium leads to the 1,2 hydroxy acid (24), whereas its sodium salt (26) is considerably more reactive and gives the 2,2-hydroxy acid (11).These observations are rationalized on the basis of the greatly enhanced ability of the COO- group relative to a COOH to stabilize an adjacent positively charged centre.The methyl substituent is also found to exert a profound effect on the nature of the solvolysis products, in hot formic acid, for example, 1-methylbicyclohex-2-yl mesylate (31) produces the formate (32) in which the substitution pattern is retained.Under milder conditions, however, the ester (31) solvolyses with rearrangement to give the 2,2-formate (33).
The Influence of Intramolecular Dynamics on Branching Ratios in Thermal Rearrangements
Newmann-Evans, Richard H.,Simon, Reyna J.,Carpenter, B. K.
, p. 695 - 711 (2007/10/02)
1- and 2-phenylbicyclohex-2-enes-5-d undergo thermal rearrangement to give products, differing only in the location of the deuterium, in ratio of about 9:1, but with identical activation enthalphies.Similarly, opticallly active trans-2-methyl-1-(trans-2-phenylethenyl)cyclopropane is found to rearrange to enantiomeric methylphenylcyclopentenes that are formed in a 5.9:1 ratio but with virtually identicyl activation enthalphies.Barring repeated coincidence, these results do not seem to be explicable within the framework of statistical theories of unimolecular kinetics such as RRKM theory, transition state theory, and variational transition state theory.The possible influence of dynamic effects in these and other unimolecular reactions is discussed.
Allylic Carbonates. Efficient Allylating Agents of Carbonucleophiles in Palladium-Catalyzed Reactions under Neutral Conditions
Tsuji, Jiro,Shimizu, Isao,Minami, Ichiro,Ohashi, Yukihiro,Sugiura, Teruo,Takahashi, Kazuhiko
, p. 1523 - 1529 (2007/10/02)
Allylation of β-keto esters or malonates was carried out in good yields under neutral conditions by using allylic carbonates in the presence of palladium-phospine catalyst.Although simple ketones, esters, nitriles, and sulfones hardly react with allylic carbonates, α-alkenyl or α-aryl ketones, esters, nitriles, and sulfones were also allylated by using palladium-bis(diphenylphosphino)ethane catalyst under neutral conditions.
Regioselectivity in Ring-Expansion of 1-Substituted Bicyclohexan-2-ones: Preferential Migration of Methylene Over Bridgehead Carbon
Della, Ernest W.,Pigou, Paul E.
, p. 2261 - 2268 (2007/10/02)
Ring expansion of several 1-substituted bicyclohexan-2-ones has been investigated in order to compare the effect od substitution on the migratory aptitude of the bridgehead carbon in relation to the methylene carbon.In the cases examined it was observed that there is a marked preference for migration of the methylene carbon, with the substituted substrates displaying higher regioselectivity that the parent ketone.In the rearrangement of both 1-fluoro- and 1-chloro-bicyclohexan-2-one, migration of the methylene carbon occurs exclusively.
