- Electrochemically driven desaturation of carbonyl compounds
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Electrochemical techniques have long been heralded for their innate sustainability as efficient methods to achieve redox reactions. Carbonyl desaturation, as a fundamental organic oxidation, is an oft-employed transformation to unlock adjacent reactivity through the formal removal of two hydrogen atoms. To date, the most reliable methods to achieve this seemingly trivial reaction rely on transition metals (Pd or Cu) or stoichiometric reagents based on I, Br, Se or S. Here we report an operationally simple pathway to access such structures from enol silanes and phosphates using electrons as the primary reagent. This electrochemically driven desaturation exhibits a broad scope across an array of carbonyl derivatives, is easily scalable (1–100 g) and can be predictably implemented into synthetic pathways using experimentally or computationally derived NMR shifts. Systematic comparisons to state-of-the-art techniques reveal that this method can uniquely desaturate a wide array of carbonyl groups. Mechanistic interrogation suggests a radical-based reaction pathway. [Figure not available: see fulltext.]
- Gnaim, Samer,Takahira, Yusuke,Wilke, Henrik R.,Yao, Zhen,Li, Jinjun,Delbrayelle, Dominique,Echeverria, Pierre-Georges,Vantourout, Julien C.,Baran, Phil S.
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p. 367 - 372
(2021/03/31)
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- Total Synthesis of (+)-Granatumine A and Related Bislactone Limonoid Alkaloids via a Pyran to Pyridine Interconversion
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We report the first total synthesis of (+)-granatumine A, a limonoid alkaloid with PTP1B inhibitory activity, in ten steps. Over the course of this study, two key methodological advances were made: a cost-effective procedure for ketone α,β-dehydrogenation using allyl-Pd catalysis, and a Pd-catalyzed protocol to convert epoxyketones to 1,3-diketones. The central tetrasubstituted pyridine is formed by a convergent Knoevenagel condensation and carbonyl-selective electrocyclization cascade, which was followed by a direct transformation of a 2H-pyran to a pyridine. These studies have led to the structural revision of two members of this family.
- Schuppe, Alexander W.,Zhao, Yizhou,Liu, Yannan,Newhouse, Timothy R.
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supporting information
p. 9191 - 9196
(2019/06/17)
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- Acceptorless dehydrogenation of C-C single bonds adjacent to functional groups by metal-ligand cooperation
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Unprecedented direct acceptorless dehydrogenation of C-C single bonds adjacent to functional groups to form α,β-unsaturated compounds has been accomplished by using a new class of group 9 metal complexes. Metal-ligand cooperation operated by the hydroxycyclopentadienyl ligand was proposed to play a major role in the catalytic transformation.
- Kusumoto, Shuhei,Akiyama, Midori,Nozaki, Kyoko
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supporting information
p. 18726 - 18729
(2014/01/06)
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- Synthesis of α,β-unsaturated carbonyl compounds via a visible-light-promoted organocatalytic aerobic oxidation
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α,β-Unsaturated ketones and aldehydes have been synthesized from their corresponding silyl enol ethers in a straightforward protocol involving a visible-light promoted organocatalytic, aerobic oxidation reaction. A cheap organic dye was used catalytically in these reactions as the photosensitizer.
- Zhang, Junlin,Wang, Leming,Liu, Qi,Yang, Zhen,Huang, Yong
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supporting information
p. 11662 - 11664
(2013/12/04)
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- Oxidative allylic rearrangement of cycloalkenols: Formal total synthesis of enantiomerically pure trisporic acid B
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Enantiomerically highly enriched unsaturated β-ketoesters bearing a quaternary stereocenter can be utilized as building blocks for the synthesis of natural occurring terpenes, i. a., trisporic acid and its derivatives. An advanced building block has been
- Dubberke, Silke,Abbas, Muhammad,Westermann, Bernhard
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p. 421 - 425
(2011/06/11)
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- A short, formal synthesis of (±)-2-pupukeanone
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A short approach to (±)-2-pukeanone, starting from 2,6-dimethylcyclohexenone employing a combination of Michael- Michael reaction and an intramolecular rhodium carbenoid C-H insertion as key reactions, is described.
- Srikrishna,Kumar, P. Ravi
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p. 152 - 153
(2007/10/03)
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- Synthesis of bicyclic homochiral dienes by allylic rearrangement of cyclohexenols - Suitable building blocks for the synthesis of nagilactones
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A very short and straightforward synthesis towards highly functionalized dienes is described. The homochiral starting material, unsaturated β-oxo ester 2, can be prepared by enzyme-catalyzed saponification. The utility of the dienes has been demonstrated in a cycloaddition with N-phenyltriazolidinone as the dienophile. The Diels-Alder reaction is highly diastereoselective, yielding only one diastereomer. VCH Verlagsgesellschaft mbH, 1997.
- Westermann, Bernhard,Dubberke, Silke
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p. 375 - 380
(2007/10/03)
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- A Simple, Effective, New, Palladium-Catalyzed Conversion of Enol Silanes to Enones and Enals
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Enol silanes derived from aldehydes and ketones are readily converted to the corresponding α,β-unsaturated carbonyl compounds by 10percent Pd(OAc)2 in the presence of one atmosphere of oxygen in DMSO as the solvent.
- Larock, Richard C.,Hightower, Timothy R.,Kraus, George A.,Hahn, Pat,Zheng, Deye
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p. 2423 - 2426
(2007/10/02)
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- A New, General Cyclopentenone Synthesis
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A new synthesis of cyclopentenones, involving an Rh(II)-catalyzed, intramolecular carbon-hydrogen insertion of diazomethyl ketones derived from α,β-unsaturated acids, is described.
- Ceccherelli, Paolo,Curini, Massimo,Marcotullio, Maria Carla,Rosati, Ornelio,Wenkert, Ernest
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p. 311 - 315
(2007/10/02)
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- A Three-Step Pyridoannelation of Carbonyl Compounds
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The elaboration of a pyridine nucleus onto an α-methylene carbonyl compound can be accomplished through a three step reaction sequence based on the regiospecific alkylation of N,N-dimethylhydrazones with bromoethyl-1,3-dioxolane.Scope and limitations of the new method are considered.
- Marchetti, Mauro
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p. 1761 - 1765
(2007/10/02)
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- Inducibility of an Enone Reductase System in the Fungus Beauveria sulfurescens: Application in Enantioselective Organic Synthesis
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Microbiological reduction of α,β-unsaturated carbonyl compounds is studied.Inducibility of the enone reductase system of Beauveria sulfurescens is reported.The best inducer is shown to be cyclohex-2-en-1-one.An appropriate procedure using induced resting mycelium is developed to reduce substituted cyclohexenones that are shown to be unable to induce the reducing enzyme.Optically pure trans-(2R,6R)-(-)-2,6-dimethylcyclohexan-1-one and trans-(2R,6R)-(-)-2,6-dimethylcyclohexan-1-ol are obtained from (+/-)-2,6-dimethylcyclohex-2-en-1-one along with optically pure (6S)-(-)-2,6-dimethylcyclohex-2-en-1-one.
- Fauve, Annie,Renard, Michel F.,Veschambre, Henri
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p. 4893 - 4897
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF (+/-) ASCOCHLORIN
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A convergent total synthesis of (+/-) ascochlorin is described.
- Safaryn, J. E.,Chiarello, J.,Chen, K.-M.,Joullie, M. M.
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p. 2635 - 2642
(2007/10/02)
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- Oxidation of Enol Silyl Ethers: Preparation of Aeginetolide, Dihydroactinidiolide, and Actinidiolide
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The preparation of the C11-terpenic lactones aeginetolide (1), dihydroactinidiolide (2), and actinidiolide (3) by using 1,3,3-trimethyl-2-(trimethylsiloxy)cyclohexene (9) as a common precursor is discussed.The key steps in the synthetic route involve the sequential m-chloroperbenzoic acid (MCPBA) oxidation and acetylation of 9 and of the siloxy diene 13 derived from 9.
- Rubottom, George M.,Juve, Henrik D.
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p. 422 - 425
(2007/10/02)
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- Electrooxidative Cleavage of Carbon-Carbon Linkages. 1. Preparation of Acylic Oxoalkanoates from 2-Hydroxy- and 2-Acetoxy-1-cycloalkanones and Cycloalkanone Enol Acetates
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A methodology is described for the synthesis of acyclic oxoalkanoates 2 by electrooxidative cleavage of carbon-carbon linkages of 2-oxocycloalkan-1-ols 1 and cycloalkanone enol acetates 3.The electrolysis of 1 was carried out in a MeOH-LiClO4-(Pt) system at a constant applied voltage of 20 V by using a divided cell, giving 2 in 82-97 percent yields.On the other hand, 3 was electrolyzed in MeOH-AcOH (10:1)-LiClO4-(Pt) at 2-8 deg to give 2 in 72-79 percent yields.Electrolysis of 4-hydroxy-p-menth-8-ene afforded methyl (3R)-3,7-dimethyl-6-oxo-7-octenoate, a chiral synthetic block for the synthesis of (+)-rose oxide, in 84 percent yield.Similarly, the procedure could be applied to the preparation of methyl(+)-6-oxo-6,7-dihydrocitronellate from (+)-menthone enol acetate (74 percent) as well as 4-hydroxy-p-menthone (94 percent).Other lithium salts, i.e., LiBF4 and CF3CO2Li, can be used for the present purpose, but there are some difficulties in producing 2 with Et4NOTs and Et4NClO4.A plausible mechanism of the formation of 2 from 1 is also discussed.
- Torii, Sigeru,Inokuchi, Tsutomu,Oi, Ryu
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- Oxydation anodique de β-cetocarboxylates en milieu aqueux ou hydroorganique. Application a la synthese de γ-dicetones, de cetones ethyleniques et de cetoamides
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A systematic study of the anodic oxidation of β-ketocarboxylate anions in aqueous or hydroorganic solvents allows to distinguish the factors directing this reaction.Thus, it is possible by the appropriate choice of reaction medium and structure of the starting ion to synthesize products such as γ diketones, ethylenic ketones and ketoamides.
- Chkir, Moncef,Lelandais, Daniel,Bacquet, Cathy
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p. 945 - 951
(2007/10/02)
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- Process for the production of (substituted) 2,6-dimethylanilines
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Aniline derivatives of the formula STR1 wherein R is hydrogen, C1 -C4 -alkyl or C1 -C4 -alkyl substituted by C1 -C2 -alkoxy are produced by reacting a N-(3-pent-2-enyl)-derivative of morpholine, piperidine or pyrrolidine with acrolein in the presence of an inert, aprotic solvent or in the absence of a solvent and heating the reaction product obtained to 100°-400° C. in the presence of a hydrogen-transfer catalyst and in the presence of an amine of the formula R--NH2, wherein R has the meaning given above.
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