25491-42-3Relevant articles and documents
Structural insights into the desymmetrization of bulky 1,2-dicarbonyls through enzymatic monoreduction
Rabuffetti, Marco,Cannazza, Pietro,Contente, Martina Letizia,Pinto, Andrea,Romano, Diego,Hoyos, Pilar,Alcantara, Andres R.,Eberini, Ivano,Laurenzi, Tommaso,Gourlay, Louise,Di Pisa, Flavio,Molinari, Francesco
supporting information, (2021/01/25)
Benzil reductases are dehydrogenases preferentially active on aromatic 1,2-diketones, but the reasons for this peculiar substrate recognition have not yet been clarified. The benzil reductase (KRED1-Pglu) from the non-conventional yeast Pichia glucozyma showed excellent activity and stereoselectivity in the monoreduction of space-demanding aromatic 1,2-dicarbonyls, making this enzyme attractive as biocatalyst in organic chemistry. Structural insights into the stereoselective monoreduction of 1,2-diketones catalyzed by KRED1-Pglu were investigated starting from its 1.77 ? resolution crystal structure, followed by QM and classical calculations; this study allowed for the identification and characterization of the KRED1-Pglu reactive site. Once identified the recognition elements involved in the stereoselective desymmetrization of bulky 1,2-dicarbonyls mediated by KRED1-Pglu, a mechanism was proposed together with an in silico prediction of substrates reactivity.
Radical N-heterocyclic carbene catalysis for β-ketocarbonyl synthesis
Ishii, Takuya,Nagao, Kazunori,Ohmiya, Hirohisa
, (2021/06/07)
N-Heterocyclic carbene-catalyzed radical cross-coupling between aldehydes and α-bromoesters or α-bromoamides is described. β-Ketocarbonyl compounds having a quaternary carbon center at the α-position can be synthesized under mild reaction conditions. Both aromatic and aliphatic aldehydes are suitable acyl donors by employing proper NHC catalyst precursors.
Synthesis of Enantioenriched α,α-Difluoro-β-arylbutanoic Esters by Pd-Catalyzed Asymmetric Hydrogenation
Dong, Kaiwu,Feng, Sitian,Shen, Chaoren,Tang, Yitian,Yang, Chenjue
supporting information, p. 7508 - 7512 (2020/10/09)
Synthesis of optically active gem-difluorinated organic molecules attracts a great deal of interest due to their unique properties in pharmaceutical and agrochemical areas. Herein, a series of enantioenriched α,α-difluoro-β-arylbutanoic esters were prepar
Domino Aryne Annulation via a Nucleophilic-Ene Process
Xu, Hai,He, Jia,Shi, Jiarong,Tan, Liang,Qiu, Dachuan,Luo, Xiaohua,Li, Yang
supporting information, p. 3555 - 3559 (2018/03/21)
1,2-Benzdiyne equivalents possess the unique property that they can react with two arynophiles through iteratively generated 1,2- and 2,3-aryne intermediates. Upon rational modification on the second leaving group of these aryne precursors, a domino aryne annulation approach was developed through a nucleophilic-ene reaction sequence. Various benzo-fused N-heterocyclic frameworks were achievable under transition metal-free conditions with a broad substrate scope.
Hypervalent iodine(III)-Mediated oxidative decarboxylation of β,γ-unsaturated carboxylic acids
Kiyokawa, Kensuke,Yahata, Shunsuke,Kojima, Takumi,Minakata, Satoshi
supporting information, p. 4646 - 4649 (2015/01/09)
A novel oxidative decarboxylation of β,γ-unsaturated carboxylic acids mediated by hypervalent iodine(III) reagents is described. The decarboxylative C-O bond forming reaction proceeded in the presence of PhI(OAc)2 to give the corresponding allylic acetates. In addition, decarboxylative C-N bond formation was achieved by utilizing hypervalent iodine(III) reagents containing an I-N bond. Mechanistic studies suggest the unique reactivity of hypervalent iodine reagents in this ionic oxidative decarboxylation.
Generation of carbanions through stibine-metal and bismuthine-metal exchange reactions and its applications to precision synthesis of ω-end-functionalized polymers
Kayahara, Eiichi,Yamada, Hiroto,Yamago, Shigeru
supporting information; experimental part, p. 5272 - 5280 (2011/06/20)
Generation of carbanions from organostibines and organobismuthines through heteroatom-metal exchange reactions was examined from synthetic and mechanistic viewpoints. The exchange reaction proceeded spontaneously upon treatment with various organometallic reagents, such as alkyl lithiums, tetraalkyl zincates, and alkyl magnesium halides to afford the corresponding carbanions quantitatively. Due to the high reactivity of these heteroatom compounds, the exchange reactions took place exclusively even in the presence of various polar functional groups, which potentially react with organometallic species. The advantage of this method was exemplified by the end-group transformation of living polymers that bear these heteroatom species at the ω-polymer end, prepared by using organostibine and bismuthine-mediated living radical polymerizations. Various polymers that bear polar functional groups and acidic hydrogen-for example, poly(methyl methacrylate), poly(butyl acrylate), poly(N-isopropyl acrylamide), and poly(2-hydroxyethyl methacrylate)-could be used in the exchange reactions, and subsequent trapping with electrophiles afforded the corresponding polymers with controlled molecular weights, molecular weight distributions, and end-group functionalities. Competition experiments showed that organostibines and organobismuthines were among the most reactive heteroatom compounds towards organometallic reagents and that their high reactivity was responsible for the high chemoselectivity in the exchange reaction. All's well that ends well: The generation of carbanions from organostibine and -bismuthine compounds was achieved thorough a heteroatom-metal exchange reaction (see scheme). The highly chemoselective exchange reaction could be applied to precision synthesis of varieties of ω-end- functionalized polymers that possess a polar functional group.
Asymmetric hydrogenation of tert-alkyl ketones
Ohkuma, Takeshi,Sandoval, Christian A.,Srinivasan, Rajagopal,Lin, Quinghong,Wei, Yinmao,Muniz, Kilian,Noyori, Ryoji
, p. 8288 - 8289 (2007/10/03)
A combined system of RuCl2(tolbinap)(pica) and an alkaline or organic phosphazene base catalyzes asymmetric hydrogenation of sterically congested tert-alkyl ketones (TolBINAP = 2,2-bis(di-4-tolylphosphino)-1,1-binaphthyl, PICA = α-picolylamine). Hydrogenation with RuH(η1-BH4)(tolbinap)(pica) does not require any strong base. Alcoholic solvents strongly affect the catalytic efficiency. The reaction proceeds smoothly in ethanol under 1-20 atm of H2 and at room temperature with a substrate to catalyst molar ratio of up to 100000. Various aliphatic, aromatic, heteroaromatic, and olefinic tert-alkyl ketones are convertible to the corresponding chiral carbinols in high enantiomeric purity. Olefinic and heteroaromatic functions are left intact. Certain cyclic ketones are also usable. The mode of enantioface selection is consistent and predictable. Copyright
Intramolecular Photoaddition of Secondary α-(Aminoalkyl)styrenes
Lewis, Frederick D.,Bassani, Dario M.,Reddy, G. Dasharatha
, p. 6390 - 6393 (2007/10/02)
The photophysical and photochemical behavior of a series of α-styrenes with two to four methylenes separating the styryl and amino groups and an (aminoalkyl)indene have been investigated and the results compared to those for the intermolecular reaction of α-methylstyrene with diethylamine.Both inter- and intramolecular quenching of styrene fluorescence by the amine is observed, indicative of electron-transfer quenching as the initial step in these reactions.The resulting exciplex undergoes regioselective N-H proton transfer to styrene C-βyielding a biradical, in the case of the intramolecular reaction, and a radical pair, in the case of the intermolecular reaction.Biradical or radical pair combination yields styrene-amine addition products.The conformation of the intermediate exciplex is proposed to control the regioselectivity of the intramolecular N-H proton transfer process.
SELECTIVE C-ALKYLATION OF 1,3-DICARBONYL COMPOUNDS
Antonioletti, Roberto,Bonadies, Francesco,Orelli, Liliana Raquel,Scettri, Arrigo
, p. 237 - 238 (2007/10/02)
Lithium hydroxide-mediated alkylation of 1,3-dicarbonyl compounds proves to proceed with high efficiency and selectivity.
REACTIONS RELATED TO COENZYME B12 DEPENDENT REARRANGEMENTS: METAL MEDIATED FREE RADICAL ACYL MIGRATIONS IN METHYL AND CYCLOPROPYL SUBSTITUTED MODELS
Best, Wayne M.,Widdowson, David A.
, p. 5943 - 5954 (2007/10/02)
Free radicals generated from the methylmalonylcoenzyme A mutase model substrates (3) and (4) by chromium(II) reduction, or by pyrolysis of the analogous cobaloximes, underwent -migration only in the acyl series (R=Ph, Me) and not the critical ester series (R=OEt, SBu).The mechanism of the migration was implied by incorporation into (4) of the cyclopropyl ring, the opening of which demonstrated the free radical nature of rearranged intermediate.
