- COBALOXIME-MEDIATED RADICAL ALKYL-NITROALKYLANION CROSS COUPLING
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Anaerobic photolysis of aqueous ethanol solutions of alkyl cobaloximes RCoIII(dmgH)2py (dgmH = dimethylglyoxime monoanion) and nitroalkyl anions caused cross coupling in which an H α to the nitro was replaced with R.
- Branchaud, Bruce P.,Yu, Gui-Xue
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- A General Approach to Intermolecular Olefin Hydroacylation through Light-Induced HAT Initiation: An Efficient Synthesis of Long-Chain Aliphatic Ketones and Functionalized Fatty Acids
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Herein, an operationally simple, environmentally benign and effective method for intermolecular radical hydroacylation of unactivated substrates by employing photo-induced hydrogen atom transfer (HAT) initiation is described. The use of commercially available and inexpensive photoinitiators (Ph2CO and NHPI) makes the process attractive. The olefin hydroacylation protocol applies to a wide array of substrates bearing numerous functional groups and many complex structural units. The reaction proves to be scalable (up to 5 g). Different functionalized fatty acids, petrochemicals and naturally occurring alkanes can be synthesized with this protocol. A radical chain mechanism is implicated in the process.
- Guin, Joyram,Paul, Subhasis
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supporting information
p. 4412 - 4419
(2021/02/05)
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- Rhodium-Catalyzed Remote Isomerization of Alkenyl Alcohols to Ketones
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We develop herein an efficient rhodium-catalyzed remote isomerization of aromatic and aliphatic alkenyl alcohols into ketones. This catalytic process, with a commercially available catalyst and ligand ([RhCl(cod)]2 and Xantphos), features high efficiency, low catalyst loading, good functional group tolerance, a broad substrate scope, and no (sub)stoichiometric additive. Preliminary mechanistic studies suggest that this transformation involves an iterative dissociative β-hydride elimination-migration insertion process.
- Dong, Wenke,Yang, Hongxuan,Yang, Wen,Zhao, Wanxiang
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- Hydroalkylation of Alkenes Using Alkyl Iodides and Hantzsch Ester under Palladium/Light System
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The hydroalkylation of alkenes using alkyl iodides with Hantzsch ester as a hydrogen source occurred smoothly under a Pd/light system, in a novel, tin-free Giese reaction. A chemoselective reaction at C(sp3)-I in the presence of a C(sp2)-X (X = Br or I) bond was attained, which allowed for the stepwise functionalization of two types of C-X bonds in a one-pot procedure.
- Sumino, Shuhei,Ryu, Ilhyong
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supporting information
p. 52 - 55
(2016/01/12)
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- Mild N-deacylation of secondary amides by alkylation with organocerium reagents
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Secondary amides are a class of highly stable compounds serving as versatile starting materials, intermediates and directing groups (amido groups) in organic synthesis. The direct deacylation of secondary amides to release amines is an important transformation in organic synthesis. Here, we report a protocol for the deacylation of secondary amides and isolation of amines. The method is based on the activation of amides with Tf2O, followed by addition of organocerium reagents, and acidic work-up. The reaction proceeded under mild conditions and afforded the corresponding amines, isolated as their hydrochloride salts, in good yields. In combination with the C-H activation functionalization methodology, the method is applicable to the functionalization of aniline as well as conversion of carboxylic derivatives to functionalized ketones.
- Wang, Ai-E.,Chang, Zong,Liu, Yong-Peng,Huang, Pei-Qiang
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supporting information
p. 1055 - 1058
(2015/09/01)
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- Borohydride-mediated radical addition reactions of organic iodides to electron-deficient alkenes
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Cyanoborohydrides are efficient reagents in the reductive addition reactions of alkyl iodides and electron-deficient olefins. In contrast to using tin reagents, the reaction took place chemoselectively at the carbon-iodine bond but not at the carbon-bromine or carbon-chlorine bond. The reaction system was successfully applied to three-component reactions, including radical carbonylation. The rate constant for the hydrogen abstraction of a primary alkyl radical from tetrabutylammonium cyanoborohydride was estimated to be 4 M-1 s-1 at 25 °C by a kinetic competition method. This value is 3 orders of magnitude smaller than that of tributyltin hydride.
- Kawamoto, Takuji,Uehara, Shohei,Hirao, Hidefumi,Fukuyama, Takahide,Matsubara, Hiroshi,Ryu, Ilhyong
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p. 3999 - 4007
(2014/05/20)
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- Small molecule probes of the receptor binding site in the Vibrio cholerae CAI-1 quorum sensing circuit
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Based on modification of separate structural features of the Vibrio cholerae quorum sensing signal, (S)-3-hydroxytridecan-4-one (CAI-1), three focused compound libraries have been synthesized and evaluated for biological activity. Modifications to the acyl tail and α-hydroxy ketone typically provided agonists with activities correlated to tail length and conservative changes to the hydroxy ketone. Among the molecules identified within this collection of agonists is Am-CAI-1 (B11), which is among the most potent agonists reported to date with an EC50 of 0.21 μM. Modifications to the ethyl side chain delivered molecules with both agonist and antagonist activity, including m-OH-Ph-CAI-1 (C13) which is the most potent antagonist reported to date with an IC50 of 36 μM. The molecules described in this manuscript are anticipated to serve as valuable tools in the study of quorum sensing in Vibrio cholerae and provide new leads in the development of an antivirulence therapy against this human pathogen.
- Bolitho, Megan E.,Perez, Lark J.,Koch, Matthew J.,Ng, Wai-Leung,Bassler, Bonnie L.,Semmelhack, Martin F.
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experimental part
p. 6906 - 6918
(2012/01/03)
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- Tin-free giese reaction and the related radical carbonylation using Alkyl iodides and cyanoborohydrides
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Tin-free Giese reaction and the related radical carbonylation process proceeded efficiently in the presence of sodium cyanoborohydride and tetrabutylammonium cyanoborohydride. The reaction took place chemoselectively at the carbon-iodine bond but not at the carbon-bromine and carbon-chlorine bonds. The iodine atom transfer followed by hydride reduction of the resulting carbon-iodine bond is proposed as a possible mechanism.
- Ryu, Ilhyong,Uehara, Shohei,Hirao, Hidefumi,Fukuyama, Takahide
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supporting information; experimental part
p. 1005 - 1008
(2009/04/07)
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- Tandem carbocupration/oxygenation of terminal alkynes
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(Chemical Equation Presented) A direct and general synthesis of α-branched aldehydes and their enol derivatives is described. Carbocupration of terminal alkynes and subsequent oxygenation with lithium tert-butyl peroxide generates a metallo-enolate. Trapping with various electrophiles provides α-branched aldehydes or stereo-defined trisubstituted enol esters or silyl ethers. The tandem carbocupration/ oxygenation tolerates alkyl and silyl ethers, esters, and tertiary amines. The reaction is effective with organocopper complexes derived from primary, secondary, and tertiary Grignard reagents and from n-butyllithium.
- Zhang, Donghui,Ready, Joseph M.
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p. 5681 - 5683
(2007/10/03)
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- B-alkylcatecholboranes as a source of radicals for efficient conjugate additions to unsaturated ketones and aldehydes
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Selective and efficient generation of alkyl radicals from alkenes as well as their addition to unsaturated ketones and aldehydes is reported. The method is based on a simple one-pot procedure involving the hydroboration of the alkene with catecholborane, followed by treatment with a catalytic amount of oxygen in the presence of DMPU and a radical trap. Examples of cyclization and cascade reactions are reported.
- Ollivier, Cyril,Renaud, Philippe
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p. 1468 - 1473
(2007/10/03)
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- Reactivity of α-Nitro Ketones toward Organometallic Reagents: Straightforward Synthesis of Tertiary β-Nitroalkanols
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Tertiary β-nitro alcohols can be efficiently obtained from the reaction of α-nitro ketones with 2 equiv of an organomagnesium or organolithium reagent.Unexpectedly, Grignard reagents do not deprotonate the α acidic proton of 2 but instead strongly coordinate with the carbonyl and the nitro oxygens.A second equivalent of reagent is thus necessary to carry out the addition.Magnesium reagents fail to react with open-chain α-nitro ketones because a rapid deprotonation occurs, and Grignard reagents are unable to attack monoanion 1.Organolithiums are stronger nucleophiles than organomagnesium reagents and can attack deprotonated substrates.The diastereoselectivity of the reaction depends on the reagent used.Grignard reagents produced almost exclusively trans nitroalkanols with 2, whereas organolithiums show little or no selectivity with the same substrate.Conversely, lithium reagents show excellent stereoselectivity with open-chain substrates and affords the anti diastereomer.
- Ballini, Roberto,Bartoli, Giuseppe,Gariboldi, Pierluigi V.,Marcantoni, Enrico,Petrini, Marino
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p. 3368 - 3372
(2007/10/02)
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- Synthesis of ω-Unsaturated Acids
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A short, high-yield method for the synthesis of ω-unsaturated acids have been developed that precludes any double-bond migration or hydrogenation.Key is the coupling reaction between Grignards of ω-unsaturated alkyl halides and the bromomagnesium salt of ω-bromo fatty acids.The reaction has been successfully extended to ω-bromo nitriles.The use of ω-chloro acids or α-bromo acids gives lower yields of heterocoupling products and substantial homocoupling.A catalyst study shows Li2CuCl4 to yield the most heterocoupling of several catalysts tried for the chloro acids, and Ni(II) or Cu(I) are best for the α-bromo acids.
- Mirviss, Stanley B.
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p. 1948 - 1951
(2007/10/02)
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- Oxidation of sec-Alcohols to the Corresponding Ketones by Corynebacterium equi
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Corinebacterium equi IFO 3730 was found to oxidize a wide variety of sec-alcohols, including alkanols, substituted alkanols, alkenols and cyclic alcohols, in moderate to high yields.Among them, the sec-alcohols which have longer carbon chains were oxidized more smoothly than those with smaller numbers of carbon.Although both enantiomers of unsymmetrically disubstituted carbinols were oxidized, the S form of 2-dodecanol was converted to the corresponding ketone a little faster than the other enantiomer.
- Ohta, Hiromichi,Fujiwara, Hidenori,Tsuchihashi, Gen-ichi
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p. 1509 - 1516
(2007/10/02)
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- A REGIOSPECIFIC SYNTHESIS OF TRIMETHYLSILYL ENOL ETHERS USING RHODIUM CATALYZED ISOMERIZATION OF β-TRIMETHYLSILYLALLYL ALCOHOLS
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The rhodium catalyzed isomerization of β-trimethylsilylallyl alcohols has been successfully applied for the regiospecific synthesis of trimethylsilyl enol ethers.
- Matsuda, Isamu,Sato, Susumu,Izumi, Yusuke
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p. 2787 - 2790
(2007/10/02)
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