- CARBANION-MEDIATED OXIDATIVE DEPROTECTION OF NON-ENOLIZABLE BENZYLATED AMINES
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Treatment of non-enolizable N-benzyl or N-para-methoxybenzyl amides with butyllithium generates the corresponding benzylic carbanions that can be oxidized with either molecular oxygen or MoOPH; the resulting hemi-aminals suffer loss of the corresponding aldehyde generating te products of amide dealkylation.
- Williams, Robert M.,Kwast, Ewa
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- Direct synthesis of amides from nonactivated carboxylic acids using urea as nitrogen source and Mg(NO3)2or imidazole as catalysts
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A new method for the direct synthesis of primary and secondary amides from carboxylic acids is described using Mg(NO3)2·6H2O or imidazole as a low-cost and readily available catalyst, and urea as a stable, and easy to manipulate nitrogen source. This methodology is particularly useful for the direct synthesis of primary and methyl amides avoiding the use of ammonia and methylamine gas which can be tedious to manipulate. Furthermore, the transformation does not require the employment of coupling or activating agents which are commonly required.
- Blacker, A. John,Chhatwal, A. Rosie,Lomax, Helen V.,Marcé, Patricia,Williams, Jonathan M. J.
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p. 5808 - 5818
(2020/06/21)
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- Utilizing Carbonyl Coordination of Native Amides for Palladium-Catalyzed C(sp3)?H Olefination
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PdII-catalyzed C(sp3)?H olefination of weakly coordinating native amides is reported. Three major drawbacks of previous C(sp3)?H olefination protocols, 1) in situ cyclization of products, 2) incompatibility with α-H-containing substrates, and 3) installation of exogenous directing groups, are addressed by harnessing the carbonyl coordination ability of amides to direct C(sp3)?H activation. The method enables direct C(sp3)?H functionalization of a wide range of native amide substrates, including secondary, tertiary, and cyclic amides, for the first time. The utility of this process is demonstrated by diverse transformations of the olefination products.
- Park, Hojoon,Li, Yang,Yu, Jin-Quan
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supporting information
p. 11424 - 11428
(2019/07/17)
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- Ruthenium-catalyzed reduction of N-alkoxy- and N-hydroxyamides
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A ruthenium-catalyzed reduction of N-alkoxy- and N-hydroxyamides was found to afford corresponding amides in good to high yields. A simple RuCl 3/Zn-Cu/alcohol system, without the addition of any other ligands, exhibited a high catalytic activity, and therefore the present reaction does not require a stoichiometric amount of metals or metal complexes as reductants. When β-substituted-α,β-unsaturated N-methoxyamides were employed as substrates, concurrent hydrogenation of the olefin moiety proceeded slowly with deprotection of the methoxy group. In the reduction of N-hydroxyamides, the alcoholic solvent was found to function as a hydrogen donor.
- Fukuzawa, Hiroko,Ura, Yasuyuki,Kataoka, Yasutaka
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p. 3643 - 3648
(2011/12/02)
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- Lawesson's reagent for direct thionation of hydroxamic acids: Substituent effects on LR reactivity
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To explore the generality and scope of direct thionation of hydroxamic acids (HAs), the reaction of various structurally diverse HAs with Lawesson's reagent was investigated. The yield of thiohydroxamic acid (THAs) is poor when HAs possess bulky acyl and/or N-substituents, acidic α-hydrogen atoms, or an N-phenyl ring. THAs yields were correlated with Brown sigma parameter. The relative rates of two subsequent processes kT2 and kR2 were also measured. Correlation was also found for methine proton chemical shifts of N-isopropyl benzothiohydroxamic acids.
- Przychodzen, Witold
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p. 676 - 684
(2007/10/03)
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- Encapsulated reagents for nitrosation
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(Matrix presented) A novel class of stable, mild, and size-shape-selective nitrosating agents for secondary amides is introduced. These are based on reversible entrapment and release of reactive nitrosonium species by calix[4]arenes. The NO+ encapsulation controls the reaction selectivity.
- Zyryanov, Grigory V.,Rudkevich, Dmitry M.
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p. 1253 - 1256
(2007/10/03)
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- beta-scission of the N-O bond in alkyl hydroxamate radicals: a fast radical trap.
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[reaction--see text ] The rate of the beta-scission of the N-O bond in the alkyl hydroxamate radical is faster than 2 x 10(8) s(-)(1). This reaction may be useful as a radical trap.
- Wu,Begley
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p. 1345 - 1348
(2007/10/03)
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- Reductive deprotection of allyl, benzyl and sulfonyl substituted alcohols, amines and amides using a naphthalene-catalysed lithiation
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The reaction of different protected alcohols, amines and amides with lithium and a catalytic amount of naphthalene (4 mol %) in THF at low temperature leads to their deprotection under very mild reaction conditions, the process being in many cases chemoselective.
- Alonso, Emma,Ramon, Diego J.,Yus, Miguel
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p. 14355 - 14368
(2007/10/03)
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- Cationic Carbon to Nitrogen Rearrangements in the Reactions of N-(Sulfonyloxy)amines with Aldehydes
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A series of aromatic and aliphatic aldehydes was reacted with N-((p-nitrobenzenesulfonyl)oxy)methylamine in chloroform.Products resulting from both carbon migration and hydride migration to nitrogen were isolated.The ratios of carbon to hydride migration products were used to clarify the reaction mechanism.The results support a two-step process in which cationic carbon to nitrogen rearrangements is rate determining.
- Hoffman, Robert V.,Salvador, James M.
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p. 4487 - 4490
(2007/10/02)
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- A New Mode of Reactivity of N-Methoxy-N-methylamides with Strongly Basic Reagents
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In applying N-methoxy-N-methylamides as acylating agents for carbanions, an unusual mode of reactivity was discovered.In particular, competitive transfer of a hydroxymethyl group was observed.The mechanism of this reaction is described, and involves a base induced E2 elimination of the N-methoxy-N-methylamide generating formaldehyde and the corresponding N-methylamide anion.
- Graham, Samuel L.,Scholz, Thomas H.
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p. 6269 - 6272
(2007/10/02)
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- The Acylation of Neutral Phosphoramidates
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Kinetic studies of the acylation of neutral secondary phosphoramidates by acid halides and anhydrides are reported.The reactions produce both N-acylphosphoramidates and carboxamides by cleavage of the P-N bond.The extent of the carboxamide formation varies with the strngth of the acid co-product and with steric and electronic factors associated with both the acylating agent and the nitrogen substituent of the phosphoramidate.Except for pivaloyl chloride, the presence of a base diminishes the amount of carboxamide formed.With either acid halides or anhydrides tertiary phosphoramidates produce carboxamides directly.The formation of both N-acylphosphoramidate and carboxamide follow the equation: rate = k2 .Second-order rate constants, k2, for the formation of N-acylphosphoramidates vary with the structure of the acylating agent: AcBr is 18 times more reactive than AcCl; in solvent pyridine the Hammett ρ-value for substituted benzoyl chlorides is 1.8; in solvent CCl4 Taft ρ* and δ values for substituted acid chlorides are 0.7 and 0.76 respectively.These data are best interpreted in terms of a bimolecular substitutions reaction involving nucleophilic attack by the phosphoramidate nitrogen atom at the carbonyl carbon of the acylating agent to form an N-acylphosphoramidate cation (5).Breakdown of this cation can give either the N-acylphosphoramidate via deprotonation, or the carboxamide via P-N bond cleavage.Carboxamide formation is favoured for reactions where P-N bond cleavage either relieves steric strain or the carboxamide is a good nucleofuge.Catalysis of the reaction between phosphoramidates and acetic anhydride by electrophiles such as AcX and HX is shown to involve acylation by AcX followed by a rapid re-formation of AcX from Ac2O and HX.
- Challis, Brian C.,Iley, James N.
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p. 1489 - 1494
(2007/10/02)
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- Phosphorus Compounds with Unusual Coordination, 5. - as well as -Cycloaddition Reactions to a Kinetically Stabilized Phosphaalkene
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Aliphatic diazo compounds display different reactivity towards the phosphaalkene 9: diazomethane, diazoethane and tert-butyl diazoacetate (10a-c) formally react with Si/P-insertion to give the hitherto unknown phosphaalkenes 12a-c.In contrast, 1-diazo-2,2-dimethylpropane (10d) and diazotrimethylsilylmethane (10e) lead to the 1,2,4-diazaphospholes 15 and 17, respectively, if the primary products (11d, 14) are treated with sodium hydroxide in tetrahydrofuran.The reaction of the nitrile oxides 18a-c with 9 yields the 1,2,4-oxazaphospholes 20a-c; the cycloadducts 19a-c are assumed to occur as intermediates, which eliminate hexamethylsiloxane either spontaneously (19a, b) or with OH(-)-catalysis.Azide dipoles (21a-c) add to 9 with formation of 4,5-dihydro-1,2,3,4-phospholes (22a-c) which - instead of aromatization by hexamethyldisiloxane elimination - prefer fragmentation to 23 (-->25) and imidoesters 24a-c; hydrolysis produces the pivaloyl amides 26a-c.The 1:2 reaction between 9 and the o-quinones 31a-d proceeds via cycloadducts (32a-d) to produce the phosphoranes 34a-d by a subsequent cycloaddition process. - Key words: 1,3-Dipoles, o-Qiunones, Cycloaddition to a Phosphaalkene, Phospholes
- Zurmuehlen, Frank,Roesch, Wolfgang,Regitz, Manfred
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p. 1077 - 1086
(2007/10/02)
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