72029-30-2Relevant articles and documents
Asymmetric Epoxidation of Enones Promoted by Dinuclear Magnesium Catalyst
Jaszczewska-Adamczak, Joanna A.,Mlynarski, Jacek
supporting information, p. 4247 - 4255 (2021/07/17)
Asymmetric synthesis with cheaper and non-toxic alkaline earth metal catalysts is becoming an important and sustainable alternative to conventional catalytic methodologies mostly relying on precious metals. In spite of some sustainable methods for enantioselective epoxidation of enones, the development of a well-defined and efficient catalyst based on magnesium complexes for these reactions is still a challenging task. In this perspective, we present the application of chiral dinuclear magnesium complexes for asymmetric epoxidation of a broad range of electron-deficient enones. We demonstrate that the in situ generated magnesium-ProPhenol complex affords enantioenriched oxiranes in high yields and with excellent enantioselectivities (up to 99% ee). Our extensive study verifies the literature data in this area and provides a step forward to better understand the factors controlling the oxygenation process. Elaborated catalyst offers mild reaction conditions and a truly wide substrate scope. (Figure presented.).
Efficient and Divergent Total Synthesis of (-)-Epicoccin G and (-)-Rostratin A Enabled by Double C(sp3)-H Activation
Thesmar, Pierre,Baudoin, Olivier
supporting information, p. 15779 - 15783 (2019/10/14)
Dithiodiketopiperazines are complex polycyclic natural products possessing a variety of interesting biological activities. Despite their interest, relatively few total syntheses have been completed. We herein report the enantioselective, scalable, and divergent total synthesis of two symmetrical pentacyclic dithiodiketopiperazines, (-)-epicoccin G and (-)-rostratin A. A common intermediate was synthesized on a multigram scale from inexpensive, commercially available starting materials using an enantioselective organocatalytic epoxidation and a double C(sp3)-H activation as key steps, with the latter allowing the efficient simultaneous construction of the two five-membered rings. In addition to the cis,cis-fused target (-)-epiccocin G, the more challenging (-)-rostratin A, possessing two trans ring junctions, was obtained for the first time on a 500 mg scale through the optimization of each step and validation on multigram quantities. Both natural products were synthesized with high overall yields (13-20%). This study should facilitate access to this fascinating and yet understudied family of biologically active natural products.
Regioselective and Stereospecific Copper-Catalyzed Deoxygenation of Epoxides to Alkenes
Yu, Jingxun,Zhou, Yu,Lin, Zhenyang,Tong, Rongbiao
supporting information, p. 4734 - 4737 (2016/09/28)
Two copper salts (Cu(CF3CO2)2 and IMesCuCl) were identified as earth-abundant, inexpensive, but effective metal catalysts together with diazo malonate for chemo-/regioselective and stereospecific deoxygenation of various epoxides with tolerance of common functional groups (alkene, ketone, ester, p-methoxybenzyl, benzyl, tert-butyldimethylsilyl, and triisopropylsilyl). In particular, the unprecedented regioselectivity allowed for the first time monodeoxygenation of diepoxides to alkenyl epoxides. Density functional theory mechanistic studies showed that the deoxygenation occurred by collapsing the free ylide, unfavoring the possible intuitive pathway via cycloreversion of possible oxetane.
Iron Catalyzed Highly Enantioselective Epoxidation of Cyclic Aliphatic Enones with Aqueous H2O2
Cussó, Olaf,Cianfanelli, Marco,Ribas, Xavi,Klein Gebbink, Robertus J. M.,Costas, Miquel
supporting information, p. 2732 - 2738 (2016/03/12)
An iron complex with a C1-symmetric tetradentate N-based ligand catalyzes the asymmetric epoxidation of cyclic enones and cyclohexene ketones with aqueous hydrogen peroxide, providing the corresponding epoxides in good to excellent yields and enantioselectivities (up to 99% yield, and 95% ee), under mild conditions and in short reaction times. Evidence is provided that reactions involve an electrophilic oxidant, and this element is employed in performing site selective epoxidation of enones containing two alkene sites.
Synthesis of 2-nickela(II)oxetanes from nickel(0) and epoxides: Structure, reactivity, and a new mechanism of formation
Desnoyer, Addison N.,Bowes, Eric G.,Patrick, Brian O.,Love, Jennifer A.
supporting information, p. 12748 - 12751 (2015/10/28)
2-Nickelaoxetanes have been frequently invoked as reactive intermediates in catalytic reactions of epoxides using nickel, but have never been isolated or experimentally observed in these transformations. Herein, we report the preparation of a series of well-defined nickelaoxetanes formed via the oxidative addition of nickel(0) with epoxides featuring ketones. The stereochemistry of the products is retained, which has not yet been reported for nickelaoxetanes. Theoretical calculations support a bimetallic ring-opening/closing pathway over a concerted oxidative addition. Initial reactivity studies of a nickelaoxetane demonstrated protonolysis, oxidatively induced reductive elimination, deoxygenation, and elimination reactions when treated with the appropriate reagents.
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.
Stereoselective epoxidation of alkenes with hydrogen peroxide using a bipyrrolidine-based family of manganese complexes
Garcia-Bosch, Isaac,Gomez, Laura,Polo, Alfonso,Ribas, Xavi,Costas, Miquel
supporting information; experimental part, p. 65 - 70 (2012/03/27)
Novel manganese complexes containing N4-tetradentate ligands derived from chiral bipyrrolidinediamines catalyze the stereoselective epoxidation of a wide array of alkenes using low catalyst loadings (0.1 mol%) and hydrogen peroxide (1.2 equiv.) as terminal oxidant. This family of catalysts affords good to excellent yields (80-100%) and moderate to good ees (40-73%) in short reaction times (30 min) making efficient use of hydrogen peroxide.
Highly enantioselective epoxidation of α,β-unsaturated ketones catalyzed by primary-secondary diamines
Lu, Yingpeng,Zheng, Changwu,Yang, Yingquan,Zhao, Gang,Zou, Gang
supporting information; experimental part, p. 3129 - 3133 (2012/01/03)
The asymmetric epoxidation of α,β-unsaturated ketones has been achieved by using functional and readily accessible primary-secondary diamines as the catalysts, giving the useful alkyl epoxy products with good yields and high enantioselectivities (up to 99% ee). Copyright
METHOD FOR PRODUCING CHIRAL ALPHA,BETA-EPOXY KETONES
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Page/Page column 3-4, (2011/02/15)
A process is claimed for the enantioselective epoxidation of α,β-unsaturated ketones, in which a compound of the general formula I, is reacted with an oxidizing agent to form α,β-epoxy ketones of the general formula II, in which R1, R2, R3 are as defined above. The α,β-epoxy ketones of the general formula II can be obtained in good yields and outstanding enantioselectivities from α,β-unsaturated ketones of the general formula I by epoxidation with hydrogen peroxide in the presence of a chiral catalyst, such as amino compounds and their acid addition salts.
Simple strategy for synthesis of optically active allylic alcohols and amines by using enantioselective organocatalysis
Jiang, Hao,Holub, Nicole,J?rgensen, Karl Anker
experimental part, p. 20630 - 20635 (2011/10/09)
A simple organocatalytic one-pot protocol for the construction of optically active allylic alcohols and amines using readily available reactants and catalyst is presented. The described reaction is enabled by an enantioselective enone epoxidation/aziridination-Wharton-reaction sequence affording two highly privileged and synthetically important classes of compounds in an easy and benign way. The advantages of the described sequence include easy generation of stereogenic allylic centers, also including quaternary stereocenters, with excellent enantio- and diastereomeric-control and high product diversity. Furthermore, using monosubstituted enones as substrates, having moderate enantiomeric excess, the one-pot reaction sequence proceeds with an enantioenrichment of the products and high diastereoselectivity was achieved.
