- Copper-Catalyzed Annulation of Oxime Acetates with α-Amino Acid Ester Derivatives: Synthesis of 3-Sulfonamido/Imino 4-Pyrrolin-2-ones
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A copper-catalyzed annulation of oxime acetates and α-amino acid ester derivatives for the easy preparation of 4-pyrrolin-2-ones bearing a 3-amino group has been developed. This process features the oxidation of amines with oxime esters as the internal oxidant to produce the active 1,3-dinucleophilic and 1,2-dielectrophilic species concurrently. The subsequent nucleophilic cyclization realizes the efficient construction of 4-pyrrolin-2-one derivatives.
- Miao, Chun-Bao,Zheng, An-Qi,Zhou, Li-Jin,Lyu, Xinyu,Yang, Hai-Tao
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supporting information
p. 3381 - 3385
(2020/04/21)
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- Scope and mechanism of a true organocatalytic beckmann rearrangement with a boronic acid/perfluoropinacol system under ambient conditions
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Catalytic activation of hydroxyl functionalities is of great interest for the production of pharmaceuticals and commodity chemicals. Here, 2-alkoxycarbonyl- and 2-phenoxycarbonyl-phenylboronic acid were identified as efficient catalysts for the direct and chemoselective activation of oxime N-OH bonds in the Beckmann rearrangement. This classical organic reaction provides a unique approach to prepare functionalized amide products that may be difficult to access using traditional amide coupling between carboxylic acids and amines. Using only 5 mol % of boronic acid catalyst and perfluoropinacol as an additive in a polar solvent mixture, the operationally simple protocol features mild conditions, a broad substrate scope, and a high functional group tolerance. A wide variety of diaryl, aryl-alkyl, heteroaryl-alkyl, and dialkyl oximes react under ambient conditions to afford high yields of amide products. Free alcohols, amides, carboxyesters, and many other functionalities are compatible with the reaction conditions. Investigations of the catalytic cycle revealed a novel boron-induced oxime transesterification providing an acyl oxime intermediate involved in a fully catalytic nonself-propagating Beckmann rearrangement mechanism. The acyl oxime intermediate was prepared independently and was subjected to the reaction conditions. It was found to be self-sufficient; it reacts rapidly, unimolecularly without the need for free oxime. A series of control experiments and 18O labeling studies support a true catalytic pathway involving an ionic transition structure with an active and essential role for the boronyl moiety in both steps of transesterification and rearrangement. According to 11B NMR spectroscopic studies, the additive perfluoropinacol provides a transient, electrophilic boronic ester that is thought to serve as an internal Lewis acid to activate the ortho-carboxyester and accelerate the initial, rate-limiting step of transesterification between the precatalyst and the oxime substrate.
- Mo, Xiaobin,Morgan, Timothy D. R.,Ang, Hwee Ting,Hall, Dennis G.
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supporting information
p. 5264 - 5271
(2018/04/24)
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- Copper-catalyzed synthesis of thiazol-2-yl ethers from oxime acetates and xanthates under redox-neutral conditions
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A novel copper-catalyzed annulation of oxime acetates and xanthates for the synthesis of thiazol-2-yl ethers with remarkable regioselectivity has been developed. Various oxime acetates, whether derived from aryl ketones or alkyl ketones, or natural product cores are suitable for this conversion. Unique dihydrothiazoles were also obtained when both reaction sites were methine. Mechanistic studies indicated that imino copper(iii) intermediates were involved. In addition, this protocol proceeded under redox-neutral conditions and did not require additives or ligands.
- Zhu, Zhongzhi,Tang, Xiaodong,Cen, Jinghe,Li, Jianxiao,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 3767 - 3770
(2018/04/17)
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- ANTIVIRAL OXIME PHOSPHORAMIDE COMPOUNDS
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Compounds of Formula I: I and their pharmaceutically acceptable salts are useful for the inhibition of HIV reverse transcriptase. The compounds may also be useful for the prophylaxis or treatment of infection by HIV and in the prophylaxis, delay in the onset or progression, and treatment of AIDS. The compounds and their salts can be employed as ingredients in pharmaceutical compositions, optionally in combination with other antiviral agents, immunomodulators, antibiotics or vaccines.
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Page/Page column 28; 29
(2017/07/06)
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- Iron-Catalyzed Synthesis of 2H-Imidazoles from Oxime Acetates and Vinyl Azides under Redox-Neutral Conditions
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A novel and versatile method for the synthesis of 2H-imidazoles via iron-catalyzed [3 + 2] annulation from readily available oxime acetates with vinyl azides has been developed. This denitrogenative process involved N-O/N-N bond cleavages and two C-N bond formations to furnish 2,4-substituted 2H-imidazoles. This protocol was performed under mild reaction conditions and needed no additives or ligands. Furthermore, this is a green reaction involving oxime acetate as internal oxidant, acetic acid, and nitrogen as byproducts.
- Zhu, Zhongzhi,Tang, Xiaodong,Li, Jianxiao,Li, Xianwei,Wu, Wanqing,Deng, Guohua,Jiang, Huanfeng
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supporting information
p. 1370 - 1373
(2017/03/23)
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- Iminoxyl radical-based strategy for intermolecular C=O bond formation: Cross-dehydrogenative coupling of 1,3-dicarbonyl compounds with oximes
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Cross-dehydrogenative C=O coupling of 13-diketones and 1,3-keto esters with oximes was realized for the first time. The reaction proceeds in the presence of the oxidants [KMnO4, Mn(OAc)2/KMnO4, Mn(OAc)32 H2O, MnO2, Mn(acac)3, Fe(ClO4)3, Cu(ClO4)26 H 2O, Cu(NO3)22.5 H2O, and (NH 4)2Ce(NO3)6]. Twenty cross-coupling products were synthesized using potassium permanganate (KMnO4), manganese(II) acetate dihydrate [Mn(OAc)32 H2O], or the manganese(II) acetate/potassium permanganate [Mn(OAc)2/KMnO 4] system; yields are 27-92%. The synthesis can be easily scaled up to gram quantities of the target products. Apparently, the reaction proceeds via a radical mechanism in which the oxidizing agent serves to generate radicals from oximes and perform the one-electron oxidation of 1,3-dicarbonyl compounds. The formation of oxime radicals was confirmed quantitatively by electron spin resonance (ESR) spectroscopy. The coupling described in the present study is the first example of the selective intermolecular reaction involving unstable iminoxyl radicals generated in situ.
- Krylov, Igor B.,Terent'Ev, Alexander O.,Timofeev, Vladimir P.,Shelimov, Boris N.,Novikov, Roman A.,Merkulova, Valentina M.,Nikishin, Gennady I.
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supporting information
p. 2266 - 2280
(2014/07/21)
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- Europium(III) triflate-catalyzed Trofimov synthesis of polyfunctionalized pyrroles
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The synthesis of polyfunctionalized pyrroles by reaction of a ketoxime with dimethyl acetylenedicarboxylate using europium(III) triflate as the catalyst is described. Copyright
- Madabhushi, Sridhar,Vangipuram, Venkata Sairam,Mallu, Kishore Kumar Reddy,Chinthala, Narsaiah,Beeram, China Ramanaiah
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supporting information; body text
p. 1413 - 1416
(2012/07/13)
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- Microwave-assisted efficient one-step synthesis of amides from ketones and benzoxazoles from (2-hydroxyaryl) ketones with acetohydroxamic acid using sulfuric acid as the catalyst
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Efficient one-step method for the synthesis of amides directly from ketones and benzoxazoles from (2-hydroxyaryl) ketones by the reaction of acetohydroxamic acid using sulfuric acid as catalyst was described.
- Madabhushi, Sridhar,Chinthala, Narsaiah,Vangipuram, Venkata Sairam,Godala, Kondal Reddy,Jillella, Raveendra,Mallu, Kishore Kumar Reddy,Beeram, China Ramanaiah
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experimental part
p. 6103 - 6107
(2011/11/30)
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- Efficient microwave-assisted synthesis of oximes from acetohydroxamic acid and carbonyl compounds using BF3·OEt2 as the catalyst
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An efficient synthesis of oximes by reaction of carbonyls with acetohydroxamic acid using BF3·OEt2 as a catalyst is described.
- Sridhar, Madabhushi,Narsaiah, Chinthala,Raveendra, Jillella,Kondal Reddy, Godala,Kishore Kumar Reddy, Mallu,China Ramanaiah, Beeram
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scheme or table
p. 4701 - 4704
(2011/09/20)
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- Novel cis- and trans-configured bis(oxime)platinum(II) complexes: Synthesis, characterization, and cytotoxic activity
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Novel cis- and trans-configured bis(oxime)platinum(II) complexes have been synthesized and characterized by elemental analyses, IR, electrospray ionization mass spectrometry, multinuclear (1H, 13C, and 195Pt) NMR spectroscopy, and, in five cases, by X-ray diffraction. Their cytotoxicity was studied in the cisplatin-sensitive CH1 cell line as well as in inherently cisplatin-resistant SW480 cancer cells. Remarkably, every single dihalidobis(oxime)platinum(II) complex (with either a cis or trans configuration) shows a comparable cytotoxic potency in both cell lines, indicating a capacity of overcoming cisplatin resistance. Particularly strong cytotoxicities were observed in the case of trans-[PtCl2(R 2C=NOH)2] (R = Me, n-Pr, i-Pr) with IC50 values in the high nanomolar concentration range in both CH1 and SW480 cancer cells. These complexes are as potent as cisplatin in CH1 cells and up to 20 times more potent than cisplatin in SW480 cells. In comparison to transplatin, the novel compounds are up to 90 (CH1) and 120 times (SW480) more cytotoxic. The previously reported observation that the trans geometry yields a more active complex in the case of [PtCl2(Me2C=NOH)2] could be confirmed for at least two structural analogues.
- Scaffidi-Domianello, Yulia Yu.,Meelich, Kristof,Jakupec, Michael A.,Arion, Vladimir B.,Kukushkin, Vadim Yu.,Galanski, Markus,Keppler, Bernhard K.
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experimental part
p. 5669 - 5678
(2010/08/06)
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- Enantioselective synthesis of 2-isoxazolines by a One-flask conjugate addition/oxime-transfer process
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A study was conducted to demonstrate a new catalytic enantioselective method to prepare 5-substituted 2-isoxazolines that applied a small organic catalyst as the source of chirality and enabled the use of different α-β-unsaturated aldehydes as starting materials. The aldehyde and acetone oxime were added to a solution of amine and benzoic acid in toluene at 0 °C. A precooled solution of H2SO4 in MeOH was added and the resulting solution was stirred for 15 minutes at 0 °C after stirring the reaction mixture at 0 °C for the indicated period of time. A saturated aqueous solution of NaHCO3 was added and the mixture was extracted with EtOAc. The combined organic extracts were dried and concentrated, while the residue was purified by flash chromatography to afford the products. The results show that the presence of a strong acid in the reaction mixture induced the formation of similar catalytic species in the reactions.
- Pohjakallio, Antti,Pihko, Petri M.
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supporting information; experimental part
p. 3960 - 3964
(2009/11/30)
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- Regioselective synthesis of syn-oximes using 3A molecular sieves in a solventless system
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Regioselective synthesis of syn-oximes using 3A molecular sieves under solvent-free condition is described.
- Bigdeli, Mohammad A.,Nikje, Mir.M.Alavi,Jafari, Said,Heravi, Majid M.
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- Mono-deoxygenation of nitroalkanes, nitrones, and heterocyclic N-oxides by hexamethyldisilane through 1,2-elimination: Concept of 'counterattack reagent'
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Transformation of secondary nitroalkanes to ketoximes was achieved in 40-73% yields by treatment of the corresponding nitronate anions with hexamethyldisilane. In this new mono-deoxygenation process, hexamethyldisilane acted as a 'counterattack reagent'. The conversion of nitrones to imines was also achieved in 82-88% yields by use of trimethylsilyllithium. Similarly, heterocyclic N-oxides were converted to the corresponding N-heterocycles in 73-86% yields. These deoxygenation processes presumably involve a 1,2-elimination.
- Hwu, Jih Ru,Tseng, Wen Nan,Patel, Himatkumar V.,Wong, Fong Fuh,Horng, Den-Nan,Liaw, Ben Ruey,Lung Ching, Lin
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p. 2211 - 2218
(2007/10/03)
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- The catalytic Friedel-Crafts acylation reaction and the catalytic Beckmann rearrangement promoted by a Gallium(III) or an antimony(V) cationic species
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The catalytic Friedel-Crafts acylation reaction and the catalytic Beckmann rearrangement are successfully carried out by using the active cationic species dichlorogallium(III) perchlorate and tetrachloroantimonium(V) hexafluoroantimonate(V), respectively, which were generated in situ from appropriate silver, gallium(III) or antimony(V) salts.
- Harada,Ohno,Kobayashi,Mukaiyama
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p. 1216 - 1220
(2007/10/02)
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- A New Synthesis of Oxime Derivatives from Carbonyl Compounds and N,O-Bis(trimethylsilyl)hydroxylamine
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Reaction of a series of aldehydes and ketones with the potassium salt of N,O-bis(trimethylsilyl)hydroxylamine (2) gave high yields of the corresponding oximate anion 5.This anion, formed in a Peterson-type reaction, could be protonated to the oxime 7 or trapped in situ with a variety of electrophiles to give O-substituted oxime derivatives.
- Hoffman, Robert V.,Buntain, Gregory A.
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p. 831 - 833
(2007/10/02)
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- REACTION D'OXIMATION DES CETONES V. MECANISME ET EFFETS DE STRUCTURE DANS LA REACTION DE DESHYDRATATION ACIDO-CATALYSEE DES CARBINOLAMINES
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The equilibrium constants of formation and the rate constants of dehydratation of carbinolamines resulting from the addition of hydroxylamine to 19 ketones, - 5 aliphatic, 5 aromatic and 9 cyclanic -, have been measured at 25 deg C in water/methanol 60/40 v/v.We show that the acid catalyzed process predominates in the range of pH 6 to 7 for acetophenones or pH 7 to 8.5 for saturated ketones.The rate constants ratios and Hammett ρ constant of the reaction suggest an sp3 (early) transition state.The changes in rate constant are discussed in terms of torsional and non-bonding steric effects.For several hindered ketones, e.g. 3,3,5,5-tetramethylcyclohexanone, we show the existence of a steric hindrance to the approach of the catalyst; in that case the result is a strong decrease of the rate of the dehydratation.
- Lamaty, G.,Roque, J. P.,Natat, A.,Silou, T.
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p. 2667 - 2676
(2007/10/02)
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- C-Nitroso compounds. Part XXXVIII. Radical reactions of α-chloro-nitroso compounds with trialkylaluminium-ether complexes
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Ether complexes of trialkylaluminium compounds react with α-chloro-nitroso compounds via radicals which can abstract hydrogen from various solvents.In the presence of olefinic solvents, radical addition to the double bond also takes place. When the trialk
- Lub, J.,Beekes, M. L.,Boer, Th. J. de
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p. 161 - 167
(2007/10/02)
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