5407-91-0Relevant articles and documents
pH Dependence of the Lifetime of a Norrish II Biradical
Caldwell, Richard A.,Dhawan, S. N.,Moore, D. E.
, p. 5163 - 5166 (1985)
The transient spectroscopy of γ-phenylbutyrophenone in a 2:1 (v/v) methanol:water mixture has been studied as a function of pH.The lifetime of the Norrish II 1,4-biradical shows an excellent titration curve.The moderately strongly absorbing acidic form of the biradical has a lifetime of 125 ns, with λmax of the difference spectrum with starting material at 320 nm.The strongly absorbing basic form has a lifetime of 62 ns and λmax 325 nm.The pKa in the mixed solvent is 11.8.The pKa in pure water, based on solvent dependence of pKa values for phenols of similar acidity, is estimated as 10.2+/-0.2, essentially identical with a value reported for the acetophenone ketyl monoradical.
Subphthalocyanine encapsulated within MIL-101(Cr)-NH2 as a solar light photoredox catalyst for dehalogenation of α-haloacetophenones
Santiago-Portillo, Andrea,Remiro-Buenama?ana, Sonia,Navalón, Sergio,García, Hermenegildo
, p. 17735 - 17740 (2019)
Subphthalocyanine has been incorporated into a robust metal-organic framework having amino groups as binding sites. The resulting SubPc?MIL-101(Cr)-NH2 composite has a loading of 2 wt%. Adsorption of subphthalocyanine does not deteriorate host crystallinity, but decreases the surface area and porosity of MIL-101(Cr)-NH2. The resulting SubPc?MIL-101(Cr)-NH2 composite exhibits a 575 nm absorption band responsible for the observed photoredox catalytic activity under simulated sunlight irradiation for hydrogenative dehalogenation of α-haloacetophenones and for the coupling of α-bromoacetophenone and styrene. The material undergoes a slight deactivation upon reuse. In comparison to the case of phthalocyanines the present study is one of the few cases showing the use of subphthalocyanine as a photoredox catalyst, with its activity derived from site isolation within the MOF cavities.
Nickel-Catalyzed Reductive Acylation of Carboxylic Acids with Alkyl Halides and N-Hydroxyphthalimide Esters Enabled by Electrochemical Process
Guo, Lin,Xia, Raymond Yang,Xia, Wujiong,Yang, Chao,Zhang, Haoxiang,Zhou, Xiao
supporting information, (2022/03/31)
A sustainable Ni-catalyzed reductive acylation reaction of carboxylic acids via an electrochemical pathway is presented, affording a variety of ketones as major products. The reaction proceeds at ambient temperature using unactivated alkyl halides and N-hydroxyphthalimide (NHP) esters as coupling partners, which exhibits several synthetic advantages, including mild conditions and convenience of amplification (58% yield for 6 mmol scale reaction). (Figure presented.).
Rh-Catalyzed Coupling of Aldehydes with Allylboronates Enables Facile Access to Ketones
Zhang, Kezhuo,Huang, Jiaxin,Zhao, Wanxiang
supporting information, (2022/02/21)
We present herein a novel strategy for the preparation of ketones from aldehydes and allylic boronic esters. This reaction involves the allylation of aldehydes with allylic boronic esters and the Rh-catalyzed chain-walking of homoallylic alcohols. The key to this successful development is the protodeboronation of alkenyl borylether intermediate via a tetravalent borate anion species in the presence of KHF2 and MeOH. This approach features mild reaction conditions, broad substrate scope, and excellent functional group tolerance. Mechanistic studies also supported that the tandem allylation and chain-walking process were involved.
Direct Addition of Grignard Reagents to Aliphatic Carboxylic Acids Enabled by Bulky turbo-Organomagnesium Anilides
Colas, Kilian,Kohlhepp, Stefanie V.,Mendoza, Abraham,V. D. dos Santos, A. Catarina
supporting information, (2022/02/02)
The synthesis of ketones through addition of organometallic reagents to aliphatic carboxylic acids is a straightforward strategy that is limited to organolithium reagents. More desirable Grignard reagents can be activated and controlled with a bulky aniline-derived turbo-Hauser base. This operationally simple procedure allows the straightforward preparation of a variety of aliphatic and perfluoroalkyl ketones alike from functionalized alkyl, aryl and heteroaryl Grignard reagents.
Photocatalyzed Decarboxylative Thiolation of Carboxylic Acids Enabled by Fluorinated Disulfide
Zubkov, Mikhail O.,Kosobokov, Mikhail D.,Levin, Vitalij V.,Dilman, Alexander D.
supporting information, p. 2354 - 2358 (2022/04/07)
Thiolation of carboxylic acids using a disulfide reagent having tetrafluoropyridinyl groups is described. The light-mediated process is performed using an acridine-type photocatalyst. Primary, secondary, tertiary, and heteroatom-substituted carboxylic acids can be thiolated, and the method can be applied to the late-stage modification of a range of naturally occurring compounds and drugs. The fluorinated pyridine fragment is believed to enable the C-S bond formation. The resulting sulfides were used as redox-active radical precursors.
Selective electrochemical oxidation of aromatic hydrocarbons and preparation of mono/multi-carbonyl compounds
Li, Zhibin,Zhang, Yan,Li, Kuiliang,Zhou, Zhenghong,Zha, Zhenggen,Wang, Zhiyong
, p. 2134 - 2141 (2021/09/29)
A selective electrochemical oxidation was developed under mild condition. Various mono-carbonyl and multi-carbonyl compounds can be prepared from different aromatic hydrocarbons with moderate to excellent yield and selectivity by virtue of this electrochemical oxidation. The produced carbonyl compounds can be further transformed into α-ketoamides, homoallylic alcohols and oximes in a one-pot reaction. In particular, a series of α-ketoamides were prepared in a one-pot continuous electrolysis. Mechanistic studies showed that 2,2,2-trifluoroethan-1-ol (TFE) can interact with catalyst species and generate the corresponding hydrogen-bonding complex to enhance the electrochemical oxidation performance. [Figure not available: see fulltext.]
Hantzsch Ester-Mediated Photochemical Transformations in the Ketone Series: Remote C(sp3)-H Arylation and Cyclopentene Synthesis through Strain Release
Paternoga, Jan,Kühlborn, Jonas,Rossdam, Nils Ole,Opatz, Till
, p. 3232 - 3248 (2021/02/27)
A metal-free Hantzsch ester-mediated synthesis of cyclopentenylketones as well as O-hetarylketones starting from ketocyclopropanes under eco-friendly conditions was developed. The versatility of the developed conditions is shown by reacting ketocyclopropanes in both a formal [3 + 2] cycloaddition with terminal alkynes (further investigated using theoretical calculations) and a radical C-C-coupling with cyanopyridines. The newly developed methodologies were later on utilized as a downstream reaction for photogenerated cyclopropanes combining UV and visible light photochemistry. Following this procedure, a UV-driven Norrish-Yang-type reaction induces the ring strain of the intermediates, which serves as activation energy for the subsequent ring transformation.
Vinyl Azides as Radical Acceptors in the Vitamin B12-Catalyzed Synthesis of Unsymmetrical Ketones
Dworakowski, Krzysztof R.,Pisarek, Sabina,Hassan, Sidra,Gryko, Dorota
supporting information, p. 9068 - 9072 (2021/11/30)
Vinyl azides are very reactive species and as such are useful building blocks, in particular, in the synthesis of N-heterocycles. They can also serve as precursors of ketones. These form in reactions of vinyl azides with nucleophiles or radicals. We have found, however, that under light irradiation vitamin B12 catalyzes the reaction of vinyl azides with electrophiles to afford unsymmetrical carbonyl compounds in decent yields. Mechanistic studies revealed that alkyl radicals are key intermediates in this transformation.
Ground-State Electron Transfer as an Initiation Mechanism for Biocatalytic C-C Bond Forming Reactions
Fu, Haigen,Lam, Heather,Emmanuel, Megan A.,Kim, Ji Hye,Sandoval, Braddock A.,Hyster, Todd K.
supporting information, p. 9622 - 9629 (2021/07/01)
The development of non-natural reaction mechanisms is an attractive strategy for expanding the synthetic capabilities of substrate promiscuous enzymes. Here, we report an "ene"-reductase catalyzed asymmetric hydroalkylation of olefins using α-bromoketones as radical precursors. Radical initiation occurs via ground-state electron transfer from the flavin cofactor located within the enzyme active site, an underrepresented mechanism in flavin biocatalysis. Four rounds of site saturation mutagenesis were used to access a variant of the "ene"-reductase nicotinamide-dependent cyclohexanone reductase (NCR) from Zymomonas mobiles capable of catalyzing a cyclization to furnish β-chiral cyclopentanones with high levels of enantioselectivity. Additionally, wild-type NCR can catalyze intermolecular couplings with precise stereochemical control over the radical termination step. This report highlights the utility for ground-state electron transfers to enable non-natural biocatalytic C-C bond forming reactions.
