- Isomerization of N-Allyl Amides to Form Geometrically Defined Di-, Tri-, and Tetrasubstituted Enamides
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Enamides represent bioactive pharmacophores in various natural products, and have become increasingly common reagents for asymmetric incorporation of nitrogen functionality. Yet the synthesis of the requisite geometrically defined enamides remains problematic, especially for highly substituted and Z-enamides. Herein we wish to report a general atom economic method for the isomerization of a broad range of N-allyl amides to form Z-di-, tri-, and tetrasubstituted enamides with exceptional geometric selectivity. This report represents the first examples of a catalytic isomerization of N-allyl amides to form nonpropenyl disubstituted, tri- and tetrasubstituted enamides with excellent geometric control. Applications of these geometrically defined enamides toward the synthesis of cis vicinal amino alcohols and tetrasubstituted α-borylamido complexes are discussed.
- Trost, Barry M.,Cregg, James J.,Quach, Nicolas
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p. 5133 - 5139
(2017/05/04)
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- Efficient tandem process for the catalytic deprotection of N-allyl amides and lactams in aqueous media: A novel application of the bis(allyl)- ruthenium(IV) catalysts [Ru(η3:η2: η3-C12H18)Cl2] and [Ru(η3:η3-C10H16)-(μ-Cl) Cl}2]
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An operationally simple and highly efficient methodology for the removal of the allyl protecting group in amides and lactams has been developed by using the commercially available bis(allyl)-ruthenium(IV) catalysts [Ru(η3:η2:η3-C12H 18)Cl2] (C12H18 = dodeca-2,6,10-triene-1,12-diyl) and [(Ru(η3:η3- C10H16)(μ-Cl)Cl}2] (C10H 16 = 2,7-dimethylocta-2,6-diene-1,8-diyl). The tandem process, which takes place in aqueous media and proceeds in a one-pot manner, involves the initial isomerization of the C=C bond of the allyl unit and subsequent oxidative cleavage of the resulting enamide.
- Cadierno, Victorio,Gimeno, Jose,Nebra, Noel
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p. 6590 - 6594
(2008/03/13)
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- Highly selective isomerization of N-allylamides and N-allylamines
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A highly selective rhodium and ruthenium catalyzed transformation of N-allylamines and N-allylamides to the corresponding 1-propenyl derivatives is described. Strong E-selectivity in the isomerization of allylamines was observed. The first catalytic syste
- Krompiec, Stanis?aw,Pigulla, Mariola,Krompiec, Micha?,Baj, Stefan,Mrowiec-Bia?oń, Julita,Kasperczyk, Janusz
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p. 5257 - 5261
(2007/10/03)
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- Control of Regioselectivity by Chelating Substrates in Some Rhodium(I) and Rhodium(III)-catalysed Reactions of Butadiene
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Rhodium(I) catalyses the addition of butadiene to chelating substrates such as N-allylamides of organic acids, or alkylamides of but-3-enoic or pent-4-enoic acids, under mild conditions, to give linear products exclusively.No reaction occurs in the absenc
- Bocelli, Gabriele,Chiusoli, Gian Paolo,Costa, Mirco,Michelotti, Michela
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p. 1347 - 1358
(2007/10/02)
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- Synthesis of 2-Arylbenzoxazoles via the Palladium-Catalyzed Carbonylation and Condensation of Aromatic Halides and o-Aminophenols
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A new synthetic method is reported in which 2-arylbenzoxazoles can be prepared by palladium-catalyzed condensation of aryl halides with o-aminophenols followed by dehydrative cyclization.This method is tolerant of a wide variety of functional groups on either aromatic ring and gives good to excellent yields of products.An aliphatic vicinal amino alcohol gave a bis-acylated product as well as a chlorine-containing product with only a small amount of the desired 2-aryloxazole being formed.Methyl iodide and benzyl bromide gave only alkylated products.
- Perry, Robert J.,Wilson, B. David,Miller, Richard J.
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p. 2883 - 2887
(2007/10/02)
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- Heteroatom-Directed Metalation. Lithiation of N-Propenylbenzamides and N-Propenyl-o-toluamides. Novel Routes to Ortho-Substituted Primary Benzamide Derivatives and N-Unsubstituted Isoquinolin-1(2H)-ones
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Reaction of N-propenylbenzamides 4 and 9, obtained by LDA-induced isomerization of the corresponding N-allylbenzamides, 1, 8, and 14, with 2 equiv of sec-butyllithium or tert-butyllithium at low temperature regiospecifically generates the highly reactive N,ortho-dilithiated species (e.g., 5 and 17).These dilithio species react avidly with a wide spectrum of electophilic reagents, including alky halides, giving adducts which on hydrolysis with warm 50percent aqueous acetic acid are converted into ortho-substituted primary benzamides in excellent yields.Ortho-lithiation of N-propenylbenzamides is thus formally equivalent to ortho-lithiation of primary benzamides themselves.The utility of this important, previously unknown, synthetic operation is enhanced by the well-known facility with which the primary amide moiety can be transformed into other useful functional groups, as exemplified by the synthesis of 2-methoxy-6-methylbenzoic acid (12) and 2-methoxy-6-methylbenzonitrile (13) from N-propenyl-2-methoxybenzamide (9).N-Propenyl-o-toluamide (7) undergoes regiospecific dilithiation on nitrogen and on the methyl group under conditions analogous to those used for the N-propenylbenzamides.These dilithio species react with DMF or "Weinreb type" amides to give condensation products which cyclize to N-propenylisoquinolin-1(2H)-ones under mildly acidic conditions.Removal of the N-propenyl moiety under more strongly acidic conditions provides N-unsubstituted isoquinolin-1(2H)-ones with high overall efficiency.This process is exemplified by the synthesis of isoquinolin-1(2H)-one (23) and its 3-n-butyl congener 26 from N-propenyl-2-methylbenzamide (7).
- Fisher, Lawrence E.,Muchowski, Joseph M.,Clark, Robin D.
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p. 2700 - 2705
(2007/10/02)
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- Amide-directed hydrocarbonylation of N-alkenylamides and α-alkenyllactams
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The amide-directed Rh-catalyzed hydroformylation and Pd-catalyzed hydroesterification of N-allylamides give the iso-aldehyde and ester, respectively, with good regioselectivity.The Rh- and Co2Rh2(CO)12-catalyzed reactions of N-methallylamide give an 1-acyl-2-formylpyrrolidine through a novel double carbonylation and an 1-acylpyrrolidine through reductive annulation, respectively, with excellent selectivity.A cyclic hemiamidal, N-benzoyl-2-hydroxy-4-methylpyrrolidine, the key intermediate for the double carbonylation and the reductive annulation, is obtained selectively in a Rh4(CO)12-catalyzed reaction of N-methallylamide.The hydrocarbonylations of this cyclic hemiamidal catalyzed by RhCl(PPh3)3, Co2Rh2(CO)12, and Co2(CO)8 give the corresponding double carbonylation product (2-formylpyrrolidine), reductive annulation product (pyrrolidine), and amidocarbonylation product (proline), respectively, in excellent yield and selectivity.The mechanisms of the novel double carbonylation and the reductive annulation is studied on the basis of deuterium-labeling experiments, and it is found that these reactions proceed via enamide intermediate followed by extremely regioseletive metal hydride addition to the enamide.The Rh-catalyzed hydrocarbonylations of the α-methallyl-γ- and δ-lactams in triethyl orthoformate followed by treatment with TFA give the corresponding 1-azabicycloalkenones via bicyclic hemiamidals through annulation in excellent overall yields.The Co2Rh2(CO)12-catalyzed reactions of these α-methallyl lactams give the corresponding 1-azabicycloalkanones as the sole isolable products in high yields.The RhCl(PPh3)3-catalyzed hydrocarbonylation of 6-allylpiperidin-2-one givesa mixture of 1-azabicyclo and 1-azabicyclo products.However, the addition of phosphines to the Rh catalyst remarkably improves the normal selectivity (n/iso = 9) to give 1-azabicyclodec-2-en-10-one as the predominant product.
- Ojima, Iwao,Zhang, Zhaoda
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p. 253 - 276
(2007/10/02)
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