13672-64-5Relevant academic research and scientific papers
Biocatalytic access to nonracemic γ-oxo esters: Via stereoselective reduction using ene-reductases
Turrini, Nikolaus G.,Cioc, Rǎzvan C.,Van Der Niet, Daan J. H.,Ruijter, Eelco,Orru, Romano V. A.,Hall, Mélanie,Faber, Kurt
, p. 511 - 518 (2017/08/14)
The asymmetric bioreduction of α,β-unsaturated γ-keto esters using ene-reductases from the Old Yellow Enzyme family proceeds with excellent stereoselectivity and high conversion levels, covering a broad range of acyclic and cyclic derivatives. Various strategies were employed to provide access to both enantiomers, which are versatile precursors of bioactive molecules. The regioselectivity of hydride addition on di-activated alkenes was elucidated by isotopic labeling experiments and showed strong preference for the keto moiety as activating/binding group as opposed to the ester. Finally, chemoenzymatic synthesis of (R)-2-(2-oxocyclohexyl)acetic acid was achieved in high ee on a preparative scale combining enzymatic reduction followed by ester hydrogenolysis.
Direct enantioselective bronsted acid catalyzed N-acyliminium cyclization cascades of tryptamines and ketoacids
Holloway, Chloe A.,Muratore, Michael E.,Storer, R. Lan,Dixon, Darren J.
supporting information; experimental part, p. 4720 - 4723 (2010/12/25)
A direct enantio- and diastereoselective N-acyliminium cyclization cascade through chiral phosphoric acid catalyzed condensation of tryptamines with γ- and δ-ketoacid derivatives to provide architecturally complex heterocycles has been developed. The reac
Thiol-catalyzed acyl radical cyclization of alkenals
Yoshikai, Kazuya,Hayama, Tomoharu,Nishimura, Katsumi,Yamada, Ken-Ichi,Tomioka, Kiyoshi
, p. 681 - 683 (2007/10/03)
(Chemical Equation Presented) Thiol-catalyzed direct generation of acyl radicals and their intramolecular addition to olefins of alkenals gave 2-substituted five- and six-membered cyclic ketones in reasonably good yields. The combination of odorless tert-dodecanthiol and AIBN or V-40 was the initiator of choice among surveyed radical generators for the cyclization of alkenals. Aldehydes having electron-deficient olefins cyclized more easily than those having unactivated olefins.
Synthetic utility of stannyl enolates as radical alkylating agents
Miura, Katsukiyo,Fujisawa, Naoki,Saito, Hiroshi,Wang, Di,Hosomi, Akira
, p. 2591 - 2594 (2007/10/03)
(Equation presented) The radical-initiated β-ketoalkylation of haloalkanes with tributylstannyl enolates is described. Stannyl enolates derived from aromatic ketones are reactive toward the homolytic β-ketoalkylation of simple haloalkanes as well as those activated by an electron-withdrawing group. The reactivity of stannyl enolates as radical alkylating agents can be utilized for an efficient three-component coupling reaction among stannyl enolates, haloalkanes, and electron-deficient alkenes.
Stereoselectivity in hydrosilylative reduction of substituted cyclohexanone derivatives with chiral rhodium-bis(oxazolinyl)pyridine catalyst
Nishiyama,Park,Itoh
, p. 1029 - 1034 (2007/10/02)
Stereoselectivity in the reduction of substituted cyclohexanones, 4-tert-butylcyclohexanone, 2-methylcyclohexanone, 2-phenylcyclohexanone, and 2-methoxycarbonyl-methylcyclohexanone, was examined with chiral rhodium-bis(oxazolinyl)pyridine catalyst and diphenylsilane. 4-tert-Butylcyclohexanone gave the corresponding trans(equatorial)-alcohol predominantly; the ratio of the trans/cis alcohols, 67:33. Other 2-substituted cyclohexanones showed exclusive enantioselectivities for each diastereomer in terms of the kinetic resolution; e.g. from 2-phenylcyclohexanone, 99% ee of (1S,2R)-trans-2-phenylcyclohexanol and 96% ee of (1S,2S)-cis-2-phenylcyclohexanol in 92% yield (the trans/cis ratio = 51:49).
Catalytic Hydrogenolysis of Methyl 2-Siloxycyclopropanecarboxylates: Investigations Regarding Chemoselectivity, Regioselectivity, and Stereoselectivity
Brueckner, Christiane,Reissig, Hans-Ulrich
, p. 617 - 626 (2007/10/02)
Alkyl-substituted methyl 2-(trimethylsiloxy)cyclopropanecarboxylates 8a - 8f are opened by hydrogen in the presence of palladium on carbon affording 4-oxoalkanoic esters 10a - 10e by desilylation. 2-Phenyl-substituted cyclopropanes 8g - 8j, however, provide 4-phenylbutanoic esters 13g - 13j under these conditions.Formation of 13j is not stereoselective.Here the primary cyclopropane cleavage is followed by hydrogenolysis of the benzylic C-O bond.This subsequent reaction can be suppressed in the case of 8g by poisoning the catalyst with triethylamine; otherwise the tert-butyldimethylsiloxy compounds 11g - 11i have to be used.Butanoic esters 14h and 14i, respectively, are formed as mixtures of diastereomeres, which is another indication for nonstereoselective hydrogenolysis of cyclopropanes.Whereas slow desilylation by hydrogen was observed with the 3-phenyl-substituted cyclopropane derivative 8k, the vinylcyclopropane 8m in part suffers cleavage of the 1-3 bond of the three-membered ring.Regio- and stereoselectivity of the hydrogenolysis of the donor-acceptor-substituted cyclopropanes 8 and 11 are discussed.
Allylic Displacements and a Novel Ester-Ether Interchange in Fused Cyclobutanones
Hassner, Alfred,Dillon, John
, p. 3315 - 3319 (2007/10/02)
Chlorophenylcyclobutanone 11, prepared by chlorophenylketene addition to cyclohexene, reacts readily with simple and hindered carboxylic acids in a cine substitution to produce keto esters 14.The acyloxy and phenyl substituents in 14c are shown by X-ray diffraction to be cis oriented; nevertheless 14 reacts with NaOMe at 20 deg C by an unusual ester-ether interchange to produce 15 and the released carboxylate RCO2-.These reactions apparently proceed via an oxyallyl cation intermediate.The behaviors of related cyclobutanones 4, 6, and 11 with methoxide are contrasted.
Ring Opening Reactions of Methyl 2-Siloxycyclopropanecarboxylates to Oxoalkanoic Acid Derivatives
Kunkel, Elisabeth,Reichelt, Ingrid,Reissig, Hans-Ulrich
, p. 802 - 819 (2007/10/02)
A great variety of methyl 2-(trialkylsiloxy)cyclopropanecarboxylates C1 - C31 are cleaved under very mild conditions and with excellent yields providing 4-oxoalkanoic esters D1 - D31 which are important synthetic building blocks.Even sensible esters with formyl, vinyl ketone, or trimethylsiloxy functions can be prepared.Corresponding to the regioselective synthesis of C isomeric pairs of D can deliberately be constructed.In the presence of an electrophile alkylating ring opening delivers 4-oxoalkanoates substituted in position 2, however, the degree of alkylation does not exceed 60percent.Several other cleavage variations allow syntheses of other 4-oxoalkanoic acid derivatives in effective one-pot procedures.
Tris(dialkylamino)sulfonium Enolates. Synthesis, Structure, and Reactions
Noyori, R.,Nishida, I.,Sakata, J.
, p. 1598 - 1608 (2007/10/02)
A mixture of an enol trimethylsilyl ether and a fluoride salt exists in a dynamic equilibrium with an enolate species and fluorotrimethylsilane.Evacuation of an equimolar mixture of an enol trimethylsilyl ether of benzyl methyl ketone and tris(diethylamino)sulfonium (TAS) difluorotrimethylsiliconate produces fluorotrimethylsilane as the volatile fraction and the corresponding TAS enolate as air-sensitive crystals.The conductivity measurement and the 1H and 13C NMR analysis have substantiated the ionic nature of the TAS enolate in THF.The NMR chemical shifts are interpreted in terms of the electron distribution.The isolated TAS enolate undergoes O-acetylation with acetic anhydride and C-alkylation with methyl iodide exclusively.TAS enolate intermediates generated in situ from a series of enol silyl ethers and TAS difluorotrimethylsiliconate react with various active organic halides under mild conditions to give the regiospecific C-alkylation products.The in situ formed enolates react with aldehyde substrates to afford the β-trimethylsiloxy ketone adducts.In most cases, the reaction is kinetically controlled and the major products have erythro stereochemistry regardless of enolate configuration.This aldol reaction is postulated to proceed via an acyclic, extended transition state, in contrast to ordinary aldol reactions of Lewis acid coordinated enolates, which take place by way of six-membered chelate transition states.
THE METHOXYCARBONYLALKYLATION AND METHOXYCARBONYLALKYLIDENATION OF SILYL ENOL ETHERS
Fleming, Ian,Iqbal, Javed
, p. 327 - 328 (2007/10/02)
Silyl enol ethers (1) react with the phenylthio(methoxycarbonyl)alkyl chlorides (2) in the presence of Lewis acids to give good yields of the γ-ketoesters (3); oxidative and reductive desulphurisations give the saturated (4) and unsaturated (5 or 6) γ-ket
