23396-36-3Relevant academic research and scientific papers
Asymmetric Synthesis of 2,3-Disubstituted Cyclic Ketones by Enantioselective Conjugate Radical Additions
Nad, Sukanya,Sibi, Mukund P.
, (2019)
Enantioselective conjugate radical addition to 2-acyloxymethyl cycloalkenones proceeds in high yield with outstanding diastereoselectivity and excellent enantioselectivity using chiral salen Lewis acids. The process provides access to 2,3-disubstituted cycloalkanones, a structural motif present in natural products.
CONJUGATE ADDITIONS TO α,β-UNSATURATED CARBONYL COMPOUNDS IN AQUEOUS MEDIA
Petrier, C.,Dupuy, C.,Luche, J. L.
, p. 3149 - 3152 (1986)
Alkyl halides in the presence of zinc copper couple add smoothly to α-enones and α-enals in aqueous solvents.Sonication enhances the efficiency of the process, which leads to the conjugate adducts in high yields.The reaction follows most probably a radical pathway, and can be used for the addition of functionalized groups.
Deciphering Reactivity and Selectivity Patterns in Aliphatic C-H Bond Oxygenation of Cyclopentane and Cyclohexane Derivatives
Martin, Teo,Galeotti, Marco,Salamone, Michela,Liu, Fengjiao,Yu, Yanmin,Duan, Meng,Houk,Bietti, Massimo
supporting information, p. 9925 - 9937 (2021/06/30)
A kinetic, product, and computational study on the reactions of the cumyloxyl radical with monosubstituted cyclopentanes and cyclohexanes has been carried out. HAT rates, site-selectivities for C-H bond oxidation, and DFT computations provide quantitative information and theoretical models to explain the observed patterns. Cyclopentanes functionalize predominantly at C-1, and tertiary C-H bond activation barriers decrease on going from methyl- and tert-butylcyclopentane to phenylcyclopentane, in line with the computed C-H BDEs. With cyclohexanes, the relative importance of HAT from C-1 decreases on going from methyl- and phenylcyclohexane to ethyl-, isopropyl-, and tert-butylcyclohexane. Deactivation is also observed at C-2 with site-selectivity that progressively shifts to C-3 and C-4 with increasing substituent steric bulk. The site-selectivities observed in the corresponding oxidations promoted by ethyl(trifluoromethyl)dioxirane support this mechanistic picture. Comparison of these results with those obtained previously for C-H bond azidation and functionalizations promoted by the PINO radical of phenyl and tert-butylcyclohexane, together with new calculations, provides a mechanistic framework for understanding C-H bond functionalization of cycloalkanes. The nature of the HAT reagent, C-H bond strengths, and torsional effects are important determinants of site-selectivity, with the latter effects that play a major role in the reactions of oxygen-centered HAT reagents with monosubstituted cyclohexanes.
Counterion Enhanced Organocatalysis: A Novel Approach for the Asymmetric Transfer Hydrogenation of Enones
Scharinger, Fabian,Márk Pálv?lgyi, ádám,Zeindlhofer, Veronika,Schnürch, Michael,Schr?der, Christian,Bica-Schr?der, Katharina
, p. 3776 - 3782 (2020/06/22)
We present a novel strategy for organocatalytic transfer hydrogenations relying on an ion-paired catalyst of natural l-amino acids as main source of chirality in combination with racemic, atropisomeric phosphoric acids as counteranion. The combination of a chiral cation with a structurally flexible anion resulted in a novel chiral framework for asymmetric transfer hydrogenations with enhanced selectivity through synergistic effects. The optimized catalytic system, in combination with a Hantzsch ester as hydrogen source for biomimetic transfer hydrogenation, enabled high enantioselectivity and excellent yields for a series of α,β-unsaturated cyclohexenones under mild conditions. Moreover, owing to the use of readily available and chiral pool-derived building blocks, it could be prepared in a straightforward and significantly cheaper way compared to the current state of the art.
Stereochemical Insights into the Anaerobic Degradation of 4-Isopropylbenzoyl-CoA in the Denitrifying Bacterium Strain pCyN1
Küppers, Julian,Becker, Patrick,Jarling, René,D?rries, Marvin,Caki?, Nevenka,Schmidtmann, Marc,Christoffers, Jens,Rabus, Ralf,Wilkes, Heinz
supporting information, p. 4722 - 4731 (2019/03/13)
The constitutions and absolute configurations of two previously unknown intermediates, (1S,2S,4S)-2-hydroxy-4-isopropylcyclohexane-1-carboxylate and (S)-3-isopropylpimelate, of anaerobic degradation of p-cymene in the bacterium Aromatoleum aromaticum pCyN
Readily Accessible Bulky Iron Catalysts exhibiting Site Selectivity in the Oxidation of Steroidal Substrates
Font, David,Canta, Mercè,Milan, Michela,Cussó, Olaf,Ribas, Xavi,Klein Gebbink, Robertus J. M.,Costas, Miquel
supporting information, p. 5776 - 5779 (2016/05/09)
Bulky iron complexes are described that catalyze the site-selective oxidation of alkyl C-H bonds with hydrogen peroxide under mild conditions. Steric bulk at the iron center is introduced by appending trialkylsilyl groups at the meta-position of the pyridines in tetradentate aminopyridine ligands, and this effect translates into high product yields, an enhanced preferential oxidation of secondary over tertiary C-H bonds, and the ability to perform site-selective oxidation of methylenic sites in terpenoid and steroidal substrates. Unprecedented site selective oxidation at C6 and C12 methylenic sites in steroidal substrates is shown to be governed by the chirality of the catalysts.
Pichia stipitis OYE 2.6 variants with improved catalytic efficiencies from site-saturation mutagenesis libraries
Patterson-Orazem, Athéna,Sullivan, Bradford,Stewart, Jon D.
, p. 5628 - 5632 (2015/01/09)
An earlier directed evolution project using alkene reductase OYE 2.6 from Pichia stipitis yielded 13 active site variants with improved properties toward three homologous Baylis-Hillman adducts. Here, we probed the generality of these improvements by testing the wild-type and all 13 variants against a panel of 16 structurally-diverse electron-deficient alkenes. Several substrates were sterically demanding, and as hoped, creating additional active site volume yielded better conversions for these alkenes. The most impressive improvement was found for 2-butylidenecyclohexanone. The wild-type provided less than 20% conversion after 24 h; a triple mutant afforded more than 60% conversion in the same time period. Moreover, even wild-type OYE 2.6 can reduce cyclohexenones with very bulky 4-substituents efficiently.
Site-selective oxidation of unactivated C sp 3-H bonds with hypervalent iodine(III) reagents
Moteki, Shin A.,Usui, Asuka,Zhang, Tiexin,Solorio Alvarado, Cesar R.,Maruoka, Keiji
supporting information, p. 8657 - 8660 (2013/09/12)
By design: The site-selective oxidation of unactivated secondary C sp 3-H bonds was accomplished with hypervalent iodine(III) reagents and tert-butyl hydroperoxide (see scheme). The preparation and derivatization of the hypervalent iodine(III) reagent are simple, thus allowing the rational design of these reagents to optimize the site selectivity of the oxidation. Copyright
Catalytic enantioselective conjugate addition of Grignard reagents to cyclic enones using C1-1,1′-bisisoquinoline-based chiral ligands
Qi, Gao,Judeh, Zaher M.A.
experimental part, p. 1585 - 1592 (2012/05/04)
New highly constrained chiral C1-1,1′-bisisoquinoline ligands were examined in the enantioselective conjugate addition of Grignard reagents to cyclohexenone and cyclopentenone. The desired 1,4-adducts were obtained in excellent yield and moderate enantiomeric excess (up to 35%). Copyright Taylor & Francis Group, LLC.
Preparation and characterization of new C2- and C 1-symmetric nitrogen, oxygen, phosphorous, and sulfur derivatives and analogs of TADDOL. part i
Pichota, Arkadius,Gramlich, Volker,Beck, Albert K.,Seebach, Dieter
experimental part, p. 1239 - 1272 (2012/09/21)
The chloro alcohols 4-6 derived from TADDOLs (=α,α, α′,α′-tetraaryl-1,3-dioxolan-4,5-dimethanols) are used to prepare corresponding sulfanyl alcohols, ethers, and amines (Scheme 1 and Table 1). The dithiol analog of TADDOL and derivatives thereof, 45-49,
