37973-52-7Relevant academic research and scientific papers
syn-Selective Michael Reaction of α-Branched Aryl Acetaldehydes with Nitroolefins Promoted by Squaric Amino Acid Derived Bifunctional Br?nsted Bases
Campano, Teresa E.,García-Urricelqui, Ane,Mielgo, Antonia,Palomo, Claudio,de Cózar, Abel
supporting information, p. 3604 - 3612 (2021/07/26)
Here we describe a direct access to 2,2,3-trisubstituted syn γ-nitroaldehydes by addition of α-branched aryl acetaldehydes to nitroolefins promoted by a cinchona based squaric acid-derived amino acid peptide. Different α-methyl arylacetaldehydes react with β-aromatic and β-alkyl nitroolefins to afford the Michael adducts in high enantioselectivity and syn-selectivity. NMR experiments and DFT calculations predict the reaction to occur through the intermediacy of E-enolate. The interaction between the substrates and the catalyst follows Pápai's model, wherein an intramolecular H-bond interaction in the catalyst between the NH group of one of the tert-leucines and the squaramide oxygen seems to be key for discrimination of the corresponding reaction transition states.
Rh-Catalyzed Asymmetric Hydrogenation of β-Branched Enol Esters for the Synthesis of β-Chiral Primary Alcohols
Liu, Chong,Yuan, Jing,Zhang, Jian,Wang, Zhihui,Zhang, Zhenfeng,Zhang, Wanbin
supporting information, p. 108 - 111 (2018/01/17)
An asymmetric hydrogenation of β-branched enol esters has been developed for the first time, providing a new route for the synthesis of β-chiral primary alcohols. Using a (S)-SKP-Rh complex bearing a large bite angle and enol ester substrates possessing an O-fomyl directing group, the desired products were obtained in quantitative yields and with excellent enantioselectivities.
METHODS OF PREPARING a,?-UNSATURATED OR a-HALO KETONES AND ALDEHYDES
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Paragraph 0087; 0090; 0091; 0112; 0113, (2017/07/14)
Copper(II) bromide mediated oxidation of acylated enol and use of the reaction in the synthesis of α,β-unsaturated or α-bromo ketones or aldehydes are disclosed. The method provides an efficient and practical process for manufacturing dehydrohedione (DHH) and many other versatile α,β-unsaturated or α-bromo ketones or aldehydes in large scales to avoid using precious metal compounds.
α,β-Unsaturated ketones via copper(II) bromide mediated oxidation
Sharley, James S.,Collado Pérez, Ana María,Ferri, Estela Espinos,Miranda, Amadeo Fernandez,Baxendale, Ian R.
supporting information, p. 2947 - 2954 (2016/05/19)
A protocol for effecting a rapid Saegusa-type oxidation of enol acetates is reported. This new method relies on the in situ elimination of an α-bromo intermediate to generate α,β-unsaturated ketones using copper(II) bromide. The methodology developed was applied to a range of substrates including a cyclohexanone, which could be directly converted to the corresponding phenol derivative. A catalytic system in which a non-masked ketone was successfully oxidised using substoichiometric CuBr2 was also developed as a proof of principle.
Thermal and photochemical solvolysis of (E)- and (Z)-2-phenyl-1-propenyl(phenyl)iodonium tetrafluoroborate: Benzenium and primary vinylic cation intermediates
Gronheid,Lodder,Ochiai,Sueda,Okuyama
, p. 8760 - 8765 (2007/10/03)
The thermal and photochemical solvolysis of the two stereoisomeric 2-phenyl-1-propenyl(phenyl)-iodonium tetrafluoroborates has been investigated in alcoholic solvents of varying nucleophilicity. The product profiles and rates of product formation in the thermal reaction are all compatible with a mechanism involving cleavage of the vinylic C - I bond assisted by the group in the trans position (methyl or phenyl), always leading to rearranged products. Depending on the nucleophilicity of the solvent, the primarily formed cations may or may not further rearrange to more stable isomers. The less reactive Z compound also yields some unrearranged vinyl ether product in the more nucleophilic solvents via an in-plane SN2 mechanism. The mechanism of the photolysis involves direct, unassisted cleavage of the vinylic, and aromatic, C - I bond in an SN1 mechanism. This produces a primary vinyl cation, which is partially trapped prior to rearrangement in methanol. The unrearranged vinyl ethers are mainly formed with retention of configuration via a λ3-iodonium/solvent complex in an SNi mechanism. Thermal and photochemical solvolyses of iodonium salts are complementary techniques for the generation of different cation intermediates from the same substrate.
Rhodium promoted isomerisation of allylic alkoxides: A new method for enolate anion formation
Gazzard, Lewis J.,Motherwell, William B.,Sandham, David A.
, p. 979 - 993 (2007/10/03)
Transition metal mediated isomerisation of allylic alkoxides is presented as a new method for enolate anion generation. The scope and limitations of enolate formation with the catalysts [Rh(dppe)(THF)2]+ClO4- and (Ph3P)3RhCl are explored and the synthetic potential of the methodology demonstrated in the stereoselective formation and reactions of certain ketone and aldehyde enolates.
