27539-94-2Relevant academic research and scientific papers
Copper-Catalyzed One-Pot Borylative Aldolisation β-Fluoride Elimination for the Formal Addition of Acrylates to Carbonyl Moieties
Rasson, Corentin,Stouse, Adrien,Boreux, Arnaud,Cirriez, Virginie,Riant, Olivier
supporting information, p. 9234 - 9237 (2018/06/04)
Herein, we report the copper-catalyzed domino borylation/aldolisation of methyl 2-fluoroacrylate with carbonyl compounds followed by an elimination to give Morita–Baylis–Hillman (MBH) analogues. The optimal conditions described were shown to be compatible
Allylic substitution for construction of a chiral quaternary carbon possessing an aryl group
Feng, Chao,Kobayashi, Yuichi
, p. 3755 - 3766 (2013/06/05)
Phenylcopper reagents derived from 2:1 PhMgBr/Cu(acac)2 and 3:1:1 PhMgBr/Cu(acac)2/ZnI2 were found to be highly reactive and regioselective in the allylic substitution of γ,γ- disubstituted secondary allylic picolinates designed for construction of a quaternary carbon, whereas the previous 2:1 ArMgBr/CuBr·Me2S reagent and that with ZnX2 were unsuccessful. The generality of the ArMgBr/Cu(acac)2 reagent was examined with enantiomerically enriched allylic picolinates, which furnished quaternary carbons with high efficiency in >92% regioselectivity and >97% chirality transfer. Two cyclohexanes with a quaternary carbon were synthesized by using these reagents.
Formation of quaternary stereogenic centers by copper-catalyzed asymmetric conjugate addition reactions of alkenylaluminums to trisubstituted enones
Mueller, Daniel,Alexakis, Alexandre
supporting information, p. 15226 - 15239 (2013/11/06)
Alkenylaluminums undergo asymmetric copper-catalyzed conjugate addition (ACA) to β-substituted enones allowing the formation of stereogenic all-carbon quaternary centers. Phosphinamine-copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β-substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl- and alkyl-substituted alkenyl nucleophiles. Moreover, alkyl-substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu-catalyzed ACA. Chiral synthesis made easy: The copper-catalyzed conjugate addition of alkenylaluminum reagents to 3-substituted cyclic enones allows for the formation of all-carbon chiral quaternary centers (see scheme; CuTC=copper(I) thiophene-2-carboxylate). Chiral phosphinamine (SimplePhos) ligands were found to be highly efficient for this transformation.
The cinchona primary amine-catalyzed asymmetric epoxidation and hydroperoxidation of α,β-unsaturated carbonyl compounds with hydrogen peroxide
Lifchits, Olga,Mahlau, Manuel,Reisinger, Corinna M.,Lee, Anna,Fares, Christophe,Polyak, Iakov,Gopakumar, Gopinadhanpillai,Thiel, Walter,List, Benjamin
supporting information, p. 6677 - 6693 (2013/06/05)
Using cinchona alkaloid-derived primary amines as catalysts and aqueous hydrogen peroxide as the oxidant, we have developed highly enantioselective Weitz-Scheffer-type epoxidation and hydroperoxidation reactions of α,β-unsaturated carbonyl compounds (up to 99.5:0.5 er). In this article, we present our full studies on this family of reactions, employing acyclic enones, 5-15-membered cyclic enones, and α-branched enals as substrates. In addition to an expanded scope, synthetic applications of the products are presented. We also report detailed mechanistic investigations of the catalytic intermediates, structure-activity relationships of the cinchona amine catalyst, and rationalization of the absolute stereoselectivity by NMR spectroscopic studies and DFT calculations.
A concise approach towards the bicyclo[3.3.1]nonan-9-one core present in the phloroglucin natural product hyperforin
Mehta, Goverdhan,Bera, Mrinal K.
, p. 1417 - 1420 (2008/09/18)
An approach towards the bicyclo[3.3.1]nonan-9-one core present in the bioactive phloroglucin natural product hyperforin is delineated in which the key C8 stereogenic quaternary centre is appropriately installed.
Asymmetric conjugate reduction of α,β-unsaturated ketones and esters with chiral rhodium(2,6-bisoxazolinylphenyl) catalysts
Kanazawa, Yoshinori,Tsuchiya, Yasunori,Kobayashi, Kazuki,Shiomi, Takushi,Itoh, Jun-Ichi,Kikuchi, Makoto,Yamamoto, Yoshihiko,Nishiyama, Hisao
, p. 63 - 71 (2007/10/03)
New asymmetric conjugate reduction of β,β-disubstituted α,β-unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6-bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)-4-Phenyl-3-penten-2- one and (E)-4-phenyl-4-isopropyl-3-penten-2-one were readily reduced at 60°C in 95% ee and 98 % ee, respectively, by 1 mol % of catalyst loading. (EtO) 2MeSiH proved to be the best hydrogen donor of choice. tert-Butyl (E)-β-methylcinnamate and β-isopropylcinnamate could also be reduced to the corresponding dihydrocinnamate derivatives up to 98% ee.
Challenge toward structural complexity using asymmetric catalysis: Target-oriented development of catalytic enantioselective Diels-Alder reaction
Usuda, Hiroyuki,Kuramochi, Akiyoshi,Kanai, Motomu,Shibasaki, Masakatsu
, p. 4387 - 4390 (2007/10/03)
(Chemical Equation Presented) A new method for the catalytic enantioselective Diels-Alder reaction using polysubstituted silyl enol ethers as dienes is described. High enantioselectivity (up to 92% ee) was produced using a catalyst generated from FeBr3 and AgSbF6 in a 1:2 ratio and aryl-pybox (aryl = Ph or p-ethoxyphenyl). This reaction should facilitate the enantioselective synthesis of polycyclic acylphloroglucinols such as hyperforin or garsubellin A, which are currently of interest from synthetic and medicinal points of view.
A highly chemoselective, diastereoselective, and regioselective epoxidation of chiral allylic alcohols with hydrogen peroxide, catalyzed by sandwich-type polyoxometalates: Enhancement of reactivity and control of selectivity by the hydroxy group through metal-alcoholate bonding
Adam, Waldemar,Alsters, Paul L.,Neumann, Ronny,Saha-Moeller, Chantu R.,Sloboda-Rozner, Dorit,Zhang, Rui
, p. 1721 - 1728 (2007/10/03)
Sandwich-type polyoxometalates (POMs), namely [VZnM2(ZnW9O34)2]q- [M = Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], are shown to catalyze selectively the epoxidation of chiral allylic alcohols with 30% hydrogen peroxide under mild conditions (ca. 20 °C) in an aqueous/organic biphasic system. The transition metals M in the central ring of polyoxometalate do not affect the reactivity, chemoselectivity, or stereoselectivity of the allylic alcohol epoxidation by hydrogen peroxide. Similar selectivities, albeit in significantly lower product yields, are observed for the lacunary Keggin POM [PW11O39]7-, in which a peroxotungstate complex has been shown to be the active oxidizing species. All these features support a tungsten peroxo complex rather than a high-valent transition-metal oxo species operates as the key intermediate in the sandwich-type POM-catalyzed epoxidations. On capping of the hydroxy functionality through acetylation or methylation, no reactivity of these hydroxy-protected substrates [1a(Ac) and 1a(Me)] is observed by these POMs. A template is proposed to account for the marked enhancement of reactivity and selectivity, in which the allylic alcohol is ligated through metal - alcoholate bonding, and the H2O2 oxygen source is activated in the form of a peroxotungsten complex. 1,3-Allylic strain promotes a high preference for the threo diastereomer and 1,2-allylic strain a high preference for the erythro diastereomer, whereas tungsten - alcoholate bonding furnishes high regioselectivity for the epoxidation of the allylic double bond. The estimated dihedral angle α of 50 - 70° for the metal - alcoholate-bonded template of the POM/H2O2 system provides the best compromise between 1,2A and 1,3A strain during the oxygen transfer. In contrast to acyclic allylic alcohols 1, the M-POM-catalyzed oxidation of the cyclic allylic alcohols 4 by H2O2 gives significant amounts of enone.
Chiral hydroperoxides as oxygen source in the catalytic stereoselective epoxidation of allylic alcohols by sandwich-type polyoxometalates: Control of enantioselectivity through a metal-coordinated template
Adam, Waldemar,Alsters, Paul L.,Neumann, Ronny,Saha-Moeller, Chantu R.,Seebach, Dieter,Beck, Albert K.,Zhang, Rui
, p. 8222 - 8231 (2007/10/03)
The epoxidation of allylic alcohols is shown to be efficiently and selectively catalyzed by the oxidatively resistant sandwich-type polyoxometalates, POMs, namely [WZnM2(ZnW9O 34)2]q- [M = OV(IV), Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], with organic hydroperoxides as oxygen source. Conspicuous is the fact that the nature of the transition metal M in the central ring of polyoxometalate affects significantly the reactivity, chemoselectivity, regioselectivity, and stereoselectivity of the allylic alcohol epoxidation. For the first time, it is demonstrated that the oxovanadium(IV)-substituted POM, namely [ZnW(VO)2(ZnW 9O34)2]12-, is a highly chemoselective, regioselective, and also stereoselective catalyst for the clean epoxidation of allylic alcohols. A high enantioselectivity (er values up to 95:5) has been achieved with [ZnW(VO)2(ZnW9O 34)2]12- and the sterically demanding TADOOL-derived hydroperoxide TADOOH as regenerative chiral oxygen source. Thus, a POM-catalyzed asymmetric epoxidation of excellent catalytic efficiency (up to 42 000 TON) has been made available for the development of sustainable oxidation processes. The high reactivity and selectivity of this unprecedented oxygen-transfer process are mechanistically rationalized in terms of a peroxy-type vanadium(V) template.
Pd(II)-hydrotalcite-catalyzed selective oxidation of alcohols using molecular oxygen
Uemura,Kakiuchi,Nishimura,Inoue
, p. 165 - 172 (2007/10/03)
A novel heterogenized Pd catalyst, Pd supported by hydrotalcite [Pd(II)-hydrotalcite], was synthesized by a simple operation from commercially available hydrotalcite, Pd(OAc)2 and pyridine. The catalyst was effective for the oxidation of a wide range of alcohols using molecular oxygen as a sole oxidant. With this catalytic system, various alcohols were readily converted to the corresponding aldehydes or ketones selectively in high to excellent yields. Sterically less hindered substrates were converted to the corresponding ketones much faster than the hindered ones. For example, cyclohexanol was converted to cyclohexanone in 79% yield for 15 hr, while larger-sized cyclic alcohols were oxidized to the corresponding ketones only in 32-77% yields in the same reaction time. The catalyst was also applicable to the oxidation of unsaturated alcohols such as geraniol and nerol without any isomerization of an alkenic part. Modified Pd(II)-hydrotalcite [Pd(II)-hydrotalcite(m)] could be reused several times while keeping its activity.
