1192-30-9Relevant academic research and scientific papers
Chemoenzymatic Halocyclization of γ,δ-Unsaturated Carboxylic Acids and Alcohols
Younes, Sabry H. H.,Tieves, Florian,Lan, Dongming,Wang, Yonghua,Süss, Philipp,Brundiek, Henrike,Wever, Ron,Hollmann, Frank
, (2019)
A chemoenzymatic method for the halocyclization of unsaturated alcohols and acids by using the robust V-dependent chloroperoxidase from Curvularia inaequalis (CiVCPO) as catalyst has been developed for the in situ generation of hypohalites. A broad range of halolactones and cyclic haloethers are formed with excellent performance of the biocatalyst.
n-Pentenyl Glycosides as Mediators in the Asymmetric Synthesis of Monosubstituted Chiral Nonracemic Tetrahydrofurans and γ-Lactones
Llera, Jose Manuel,Lopez, J. Cristobal,Fraser-Reid, Bert
, p. 2997 - 2998 (1990)
n-Pentenyl glycosides can be oxidatively hydrolyzed by treatment with N-bromosuccinimide, previous work having been focused on the usefulness of the resulting glycosyl moiety.In this paper, attention is focused on asymmetric induction in the 2-(bromomethyl)furan that is liberated.The enantiomeric excess depends strongly on the orientations at the anomeric centers and at C2, as well as on the protecting group on the C2 oxygen. α-Anomers display higher asymmetric induction, and rationalization of this observation is based on the assumption that the molecule reacts from the favored ground-state orientation, wherein the exo anomeric effect is displayed.The usefulness of this route to optically active furans has been probed by a synthesis of an insect pheromone from the Bledius species.
X+ transfer from the halonium ions of adamantylideneadamantane to acceptor olefins. The possibility of chiral induction in the transfer process
Neverov, Alexei A.,Muise, Theresa L.,Brown
, p. 1844 - 1850 (1997)
The bromonium ion of adamantylideneadamantane (Ad=Ad-Br+) has been used to induce the bromocyclization of a 4-pentenyl glycoside (10) and a 5-hexenyl glycoside (11) in dichloroethane. The kinetics of these processes have been studied at 25°C in the presence of varying [Ad=Ad] and, in the case of the transfer to 10, in the presence of pentanol. The second-order rate constants for bromocyclization of these two alkenes are (1.04 ± 0.06) × 10-1 M-1 s-1 and (5.34 ± 0.2) × 10-2 M-1 s-1, respectively, and in no case does added Ad=Ad or pentanol alter the reaction rate. The kinetic behavior is interpreted in terms of cyclization occurring directly from a 1:1 complex of Ad=Ad-Br+ and 10 or 11. The chiral induction for the bromocyclization of 10 promoted by AdAd-Br+ was measured at 20% e.e., the (-)-(S)-tetrahydrofurfuryl bromide being the dominant stereoisomer. Ad=Ad molecules substituted at one of the homoallylic carbons by an axial methyl group (12), or by two methyl groups (axial and equatorial), were synthesized and the 1H NMR spectra of their bromonium ions is given. These materials are not stable for prolonged times at room temperature. A limited kinetic study of the reaction of 12-Br+ and 4-pentenol indicated that the Br+ transfer is 500 times faster than the comparable transfer from Ad=Ad-Br+ to 4-pentenol. The possibility of using these materials to induce chiral bromocyclization is discussed.
A Novel Method for the Conversion of Halide Anion to the Positive Halogen by Nitrobenzenesulfonyl Peroxide. Application to Oxyhalogenation of Olefin
Yoshida, Masato,Mochizuki, Hideki,Suzuki, Takashi,Kamigata, Nobumasa
, p. 3704 - 3706 (1990)
Bromide and chloride anions could be readily oxidized into positive halogens by treating with p-nitrobenzenesulfonyl peroxide.The positive halogens, thus formed, reacted with olefins to give epihalonium ions, which were trapped by oxygen nucleophiles inter- or intramolecularly to afford oxyhalogenated compounds.
Bis-selenonium Cations as Bidentate Chalcogen Bond Donors in Catalysis
He, Xinxin,Wang, Xinyan,Tse, Ying-Lung Steve,Ke, Zhihai,Yeung, Ying-Yeung
, p. 12632 - 12642 (2021/10/21)
Lewis acids are frequently employed in catalysis but they often suffer from high moisture sensitivity. In many reactions, catalysts are deactivated because of the problem that strong Lewis acids also bond to the products. In this research, hydrolytically stable bidentate Lewis acid catalysts derived from selenonium dicationic centers have been developed. The bis-selenonium catalysts are employed in the activation of imine and carbonyl groups in various transformations with good yields and selectivity. Lewis acidity of the bis-selenonium salts was found to be stronger than that of the monoselenonium systems, attributed to the synergistic effect of the two cationic selenonium centers. In addition, the bis-selenonium catalysts are not inhibited by strong bases or moisture.
Applications of Selenonium Cations as Lewis Acids in Organocatalytic Reactions
He, Xinxin,Wang, Xinyan,Tse, Ying-Lung (Steve),Ke, Zhihai,Yeung, Ying-Yeung
supporting information, p. 12869 - 12873 (2018/09/14)
The use of trisubstituted selenonium salts as organic Lewis acids in electrophilic halogenation and aldol-type reactions has been developed. The substrate scope is broad. The reaction conditions are mild and compatible with various functionalities. This study opens a new avenue for the development of nonmetallic Lewis acid catalysis.
Synthesis, structural characterization and catalytic activity of a multifunctional enzyme mimetic oxoperoxovanadium(v) complex
Si, Tapan K.,Paul, Shiv S.,Drew, Michael G. B.,Mukherjea, Kalyan K.
scheme or table, p. 5805 - 5815 (2012/06/15)
The synthesis and structural characterization of a novel oxoperoxovanadium(v) complex [VO(O2)(PAH)(phen)] containing the ligands 2-phenylacetohydroxamic acid (PAHH) and 1,10-phenanthroline (phen) has been accomplished. The oxoperoxovanadium(v) complex was found to mimic both vanadate-dependent haloperoxidase (VHPO) activity as well as nuclease activity through effective interaction with DNA. The complex is the first example of a structurally characterized stable oxoperoxovanadium(v) complex with a coordinated bi-dentate hydroximate moiety (-CONHO-) from 2-phenylacetohydroximate (PAH). The oxoperoxovanadium(v) complex has been used as catalyst for the peroxidative bromination reaction of some unsaturated alcohols (e.g. 4-pentene-1-ol, 1-octene-3-ol and 9-decene-1-ol) in the presence of H2O2 and KBr. The catalytic products have been characterized by GC-MS analysis and spectrophotometric methods. The DNA binding of this complex has been established with CT DNA whereas the DNA cleavage was demonstrated with plasmid DNA. The interactions of the complex with DNA have been monitored by electronic absorption and fluorescence emission spectroscopy. Viscometric measurements suggest that the compound is a DNA intercalator. The nuclease activity of this complex was confirmed by gel electrophoresis studies.
Hydroalkylation of alkynyl Ethers via a gold(I)-catalyzed 1,5-hydride shift/cyclization sequence
Jurberg, Igor Dias,Odabachian, Yann,Gagosz, Fabien
supporting information; scheme or table, p. 3543 - 3552 (2010/05/01)
A series of alkynyl ethers react with an electrophilic gold(I) catalyst to produce a range of structurally complex spiro or fused dihydrofurans and dihydropyrans via a 1,5-hydride shift/cyclization sequence. This hydroalkylation process, which is performed under practical experimental conditions, can be applied to terminal as well as ester-substituted alkynes. It allows the efficient conversion of secondary or tertiary sp3 C-H bonds into new C-C bonds by the nucleophilic addition of a vinylgold species onto an oxonium intermediate. The stereoselectivity of the cycloisomerization process toward the formation of a new five- or six-membered cycle appears to be dependent on steric factors and the alkyne substitution pattern.
[3 + 2] Cycloreversion of Bicyclo[m.3.0]alkan-3-on-2-yl-1-oxonium Ylides to Alkenyloxyketenes. Stereospecific Aspect
Oku, Akira,Sawada, Yuichi,Schroeder, Marc,Higashikubo, Ichiro,Yoshida, Tomohiro,Ohki, Shigeji
, p. 1331 - 1336 (2007/10/03)
Rhodium(II)-catalyzed intramolecular reaction of diazoketones 1 bearing a cyclic ethereal moiety transiently formed bicyclo[m.3.0]octan-3-one-1-oxonium-2-ylides (2), which underwent sigmatropic and stereospecific [3 + 2] cycloreversion reaction to form alkenyloxyketenes 3. The ketenes were efficiently trapped by methanol to form the corresponding esters 4. Mechanistic studies revealed that the size of ethereal ring can be variable at least from THF to the THP, oxepane, and oxocane moiety, i.e., m = 3-6. On the other hand, the size of the ylide ring containing the carbonyl unit is limited to a five-membered ring. The cycloreversion was found to be stereospecific as was proven by the reactions of diastereoisomeric pairs bearing a methyl group at the bond-cleaving position. From threo isomers 7, (E)-alkenyloxyacetates 15 were exclusively formed (77-84%), whereas from erythro isomers 8, (Z)-isomers 16 were formed (80-88%). Mechanism of the cleavage from diazoacetonyl-substituted cyclic ethers to alkenyloxyketenes via bicyclic oxonium ylides was analyzed on the basis of calculations employing the hybrid density functional B3LYP and the highly correlated quadratic configuration interaction QCISD method to reveal that the concerted [3 + 2] cycloreversion is the key step of this reaction.
Mechanistic Evaluation of the Halocyclization of 4-Penten-1-ol by Some Bis(2-substituted pyridine) and Bis(2,6-disubstituted pyridine)bromonium Triflates
Cui, Xi-Lin,Brown
, p. 5653 - 5658 (2007/10/03)
The halocyclization reaction of 4-penten-1-ol mediated by various bis(2-substituted pyridine) and (2,6- disubstituted pyridine)bromonium triflates (P2Br+OTf-) was investigated to determine the influence of the substituents on the mechanism of reaction. In all cases, the reaction proceeds via a two-step process where the starting P2Br+ reversibly dissociates to a reactive monosubstituted PBr+, which then is captured by 4-penten-1-ol to form halocyclized product (2-bromomethyltet-rahydrofuran). The dissociation rate constant of P2Br+ (kd) is sensitive to the steric bulk at the 2- and 6-positions, and in the case of the 2,6-dicyclohexylpyridine or 2,6-dicyclopentylpyridine, the P2Br+ species are too unstable to isolate. The partitioning ratio of the reactive intermediate (PBr+) between reversal and product formation (k-d/k2) is not particularly sensitive to the nature of the pyridine, the limiting values being 3-7 except in the case of bis(2(-)-menthylpyridine)bromonium triflate where the k-d/k2 ratio is ～80. The reaction of 4-penten-1-ol and its OD isotopomer with bis(lutidine)bromonium triflate was investigated to determine the deuterium kinetic isotope effect (dkie) on the bromocyclization reaction. The (k-d/k2)H/D ratio is 1.0, indicating that the rate-limiting step for the bromocyclization is probably formation of a PBr+-4-penten-1-ol complex which does not involve substantial changes in the bonding of the OH. The cyclization of 4-penten-1-ol and 4-pentenoic acid mediated by bis(2(-)-menthylpyridine)bromonium triflate produces an enantiomeric excess in the cyclized products of only 2.4% and 4.8% respectively.
