121701-48-2Relevant academic research and scientific papers
Umpolung Synthesis of 1,3-Amino Alcohols: Stereoselective Addition of 2-Azaallyl Anions to Epoxides
Daniel, Paige E.,Weber, Alexandria E.,Malcolmson, Steven J.
supporting information, p. 3490 - 3493 (2017/07/15)
We report the direct preparation of 1,3-amino alcohols that contain up to three contiguous stereogenic centers by the umpolung coupling of imines and epoxides. Nucleophilic 2-azaallyl anions, generated from imines, are stereoselectively added to epoxides to furnish 1,3-amino alcohols after hydrolysis of the product imine. Transformations afford amino alcohols with >98% site selectivity with respect to both reaction partners and in up to >98% yield and >20:1 dr.
Lewis acid-promoted electron transfer deoxygenation of epoxides, sulfoxides, and amine N-oxides: the role of low-valent niobium complexes from NbCl5 and Zn
Oh, Kyungsoo,Knabe, William Eric
supporting information; experimental part, p. 2966 - 2974 (2009/05/30)
A mild and operationally simple deoxygenation of epoxides, sulfoxides, and amine N-oxides is described using a sub-stoichiometric amount of low-valent niobium complexes generated in situ from commercially available NbCl5 and zinc dust. The deoxygenation proceeds by a reductive cleavage of polarized O-C/O-N/O-S bonds through a single electron transfer from zinc metal to the niobium-substrate complex due to the high oxophilic nature of the niobium species. The presence of adjacent radical-stabilizing groups is beneficial to epoxide substrates; however the similar prerequisite does not apply to sulfoxides and amine N-oxides, where a broad range of substrates are efficiently deoxygenated in excellent yields.
Biomimetic iron-catalyzed asymmetric epoxidation of aromatic alkenes by using hydrogen peroxide
Gelalcha, Feyissa Gadissa,Anilkumar, Gopinathan,Tse, Man Kin,Brueckner, Angelika,Beller, Matthias
experimental part, p. 7687 - 7698 (2009/08/07)
A novel and general biomimetic non-heme Fe-catalyzed asymmetric epoxidation of aromatic alkenes by using hydrogen peroxide is reported herein. The catalyst consists of ferric chloride hexahydrate (FeCl3·OH 2O), pyridine-2,6-dicarboxylic acid (H2-(pydic)), and readily accessible chiral N-arenesulfonyl-N′-benzyl-substituted ethylenediamine ligands. The asymmetric epoxidation of styrenes with this system gave high conversions but poor enantiomeric excesses (ee), whereas larger alkenes gave high conversions and ee values. For the epoxidation of trans-stilbene (1a), the ligands (S,S)-N-(4-toluenesulfonyl)-1,2- diphenylethylenediamine ((S,S)-4a) and its N′-benzylated derivative ((S,S)-5a) gave opposite enantiomers of trans-stilbene oxide, that is, (S,S)-2a and (R,R)-2a, respectively. The enantioselectivity of alkene epoxidation is controlled by steric and electronic factors, although steric effects are more dominant. Preliminary mechanistic studies suggest the in situ formation of several chiral Fe-complexes, such as [FeCl(L*)2-(pydic)] ·HCl (L* = (S,S)-4a or (S,S)-5a in the catalyst mixture), which were identified by ESIMS. A UV/Vis study of the catalyst mixture, which consisted of FeCl3·6H2O, H2(pydic), and (S,S)-4a, suggested the formation of a new species with an absorbance peak at λ = 465 nm upon treatment with hydrogen peroxide. With the aid of two independent spin traps, we could confirm by EPR spectroscopy that the reaction proceeds via radical intermediates. Kinetic studies with deuterated styrenes showed inverse secondary kinetic isotope effects, with values of k H/kD = 0.93 for the β carbon and kH/k D=0.97 for the a carbon, which suggested an unsymmetrical transition state with stepwise O transfer. Competitive epoxidation of para-substituted styrenes revealed a linear dual-parameter Hammett plot with a slope of 1.00. Under standard conditions, epoxidation of la in the presence of ten equivalents of H218O resulted in an absence of the isotopic label in (S,S)-2a. A positive non-linear effect was observed during the epoxidation of la in the presence of (S,S)-5a and (R,R)-5a.
Arabinose-derived ketones as catalysts for asymmetric epoxidation of alkenes
Shing, Tony K. M.,Leung, Gulice Y. C.,Luk, To
, p. 7279 - 7289 (2007/10/03)
Readily available arabinose-derived ketones, containing a tunable butane-2,3-diacetal as the steric blocker, displayed increasing enantioselectivity (up to 90% ee) with the size of the acetal alkyl group in catalytic asymmetric epoxidation of trans-disubstituted and trisubstituted alkenes. The stereochemical communication between our ketone catalysts and the alkene substrates is mainly due to steric effect, and electronic effect involving π-π interaction between phenyl groups of substrate and of catalyst did not appear to be operative in our system.
Convenient method for epoxidation of alkenes using aqueous hydrogen peroxide
Man, Kin Tse,Klawonn, Markus,Bhor, Santosh,Doebler, Christian,Anilkumar, Gopinathan,Hugl, Herbert,Maegerlein, Wolfgang,Beller, Matthias
, p. 987 - 990 (2007/10/03)
(Chemical Equation Presented) The complex [Ru(tpy)(pydic)] (1a) is an active catalyst for epoxidation of alkenes by aqueous 30% hydrogen peroxide in tertiary alcohols. The protocol is simple to operate and gives the corresponding epoxides in good to excellent yields. Chiral enantiopure [Ru(tpy*)(pydic) ] complexes have been synthesized and successfully applied in this procedure.
Cyclohexanones derived from dihydrocarvone as precursor of chiral dioxiranes for epoxidation of olefins
Solladié-Cavallo, Arlette,Jierry, Lo?c,Lupattelli, Paolo,Bovicelli, Paolo,Antonioletti, Roberto
, p. 11375 - 11381 (2007/10/03)
New ketones having an axial α-fluorine atom and substituents other than fluorine at C8, derived from commercially available (+)-dihydrocarvone, have been prepared and used for epoxidations of trans stilbene, trans methyl p-methoxy cinnamate, trans cinnamyl alcohol and derivatives. It was found that replacement of the H at C8 by a substituent containing an oxygen atom increases the enantioselectivities in all cases. It was also shown that protic substituents (hydroxyl groups) provide a decrease in enantioselectivity in the case of cinnamates probably because of H-bonding dioxirane-substrate. It is noted that the absolute configurations of the various epoxides obtained hold with the usual model involving a spiro-approach on the dioxirane conformation C1 having the α-fluorine axial. Moreover, sub-stoichiometric amounts (0.3 equiv) of ketone can be used in all cases as these ketones do not undergo Baeyer-Villiger oxidation and are recovered. Graphical abstract.
Asymmetric aminolysis of aromatic epoxides: A facile catalytic enantioselective synthesis of anti-β-amino alcohols
Bartoli, Giuseppe,Bosco, Marcella,Carlone, Armando,Locatelli, Manuela,Massaccesi, Massimo,Melchiorre, Paolo,Sambri, Letizia
, p. 2173 - 2176 (2007/10/03)
The first asymmetric aminolysis of trans-aromatic epoxides with anilines is described. The process affords enantioenriched anti-β-amino alcohols in up to 99% ee. The complete regio- and diastereoselectivity observed uses commercially available [Cr(Salen)CI] as a Lewis acid catalyst and in combination with a very simple experimental procedure renders the present reaction a facile and practical tool for the synthesis of chiral nonracemic anti-β-amino alcohols.
Kinetic Resolution of Epoxides by a C-C Bond-Forming Reaction: Highly Enantioselective Addition of Indoles to cis, trans, and meso Aromatic Epoxides Catalyzed by [Cr(salen)] Complexes
Bandini, Marco,Cozzi, Pier Giorgio,Melchiorre, Paolo,Umani-Ronchi, Achille
, p. 84 - 87 (2007/10/03)
The high reactivity of indoles has led to a new approach for the kinetic resolution of epoxides. [Cr(salen)] efficiently catalyzes a new C-C bond-forming reaction that allows the kinetic resolution of cis and trans aromatic epoxides (see scheme). By employing the same catalytic system, different indolyl derivatives were obtained in high enantiomeric excesses (up to 98%) by asymmetric ring opening of meso-stilbene oxide.
Catalytic enantioselective epoxidation with arabinose-derived uloses containing tunable steric sensors
Shing, Tony K. M.,Leung, Gulice Y. C.,Yeung, Kwan W.
, p. 9225 - 9228 (2007/10/03)
Readily available arabinose-derived 4-uloses, containing a tunable butane-2,3-diacetal as the steric sensor, displayed increasing enantioselectivity (up to 93 percent ee) with the size of the acetal alkyl group in catalytic asymmetric epoxidation of trans-disubstituted and trisubstituted alkenes.
