- One-pot copper(I)-catalyzed synthesis of 3,5-disubstituted isoxazoles
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3,5-Disubstituted isoxazoles are obtained in good yields by a convenient one-pot, three-step procedure utilizing a regioselective copper(I)-catalyzed cycloaddition reaction between in situ generated nitrile oxides and terminal acetylenes. Most functional
- Hansen, Trond V.,Wu, Peng,Fokin, Valery V.
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p. 7761 - 7764
(2007/10/03)
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- Chemical partitioning agents and methods of using same
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The present invention is directed to partitioning agents and methods of using same to effectuate separation of a reactant, intermediate product, and/or final product from a reaction mixture while minimizing the need for traditional separation or isolation techniques.
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Page column 19-20
(2010/02/05)
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- Diastereoselective [3+2] cycloadditions of a camphor-derived chiral N- acryloylhydrazide with nitrile oxides: The preparation of optically pure δ2-isoxazolines
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Reaction of a novel chiral N-acryloylhydrazide with various nitrile oxides proceeded smoothly to afford the cycloadduct with high diastereoselectivity (99:1). The auxiliary can be easily removed from the cycloadducts under mild conditions. (C) 2000 Elsevier Science Ltd.
- Yang, Kung-Shuo,Lain, Jung-Chaing,Lin, Chun-Hui,Chen, Kwunmin
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p. 1453 - 1456
(2007/10/03)
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- 4,5-Dihydroisoxazole and 4,5-Dihydro-1,2,4-oxadiazole Derivatives from Cycloaddition Reactions of Nitrile Oxides to Alkyl N-(Diphenylmethylene)α,β-dehydroamino Acids
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The alkyl N-(diphenylmethylene)-α,β-dehydroamino acids 1 have been submitted to 1,3-dipolar cycloadditions with nitrile oxides.The reactivity of these compounds depends on the type and on the stereochemistry of the β-substituents.With the unsubstituted terms 1a,b the reaction occurs on the C,C double bond, providing a good method for the synthesis of the 4,5-dihydroisoxazole derivatives 3a,b,c and for the gem-functionalized 4,5-dihydroisoxazoles amino carboxylic ester 5.The β-substituted compounds 1c,d,e, inert to 1,1-dimethylethylnitrile oxide, undergo the reaction to the N,C double bond, thus giving with 2a,b the 4,5-dihydro-1,2,4-oxadiazole derivatives 4.All the reactions occur with high site- and regioselectivity.
- Balsamini, Cesarino,Spadoni, Gilberto,Bedini, Annalida,Tarzia, Giorgio,Lanfranchi, Maurizio,Pellinghelli, Maria Angela
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p. 1593 - 1598
(2007/10/02)
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- Cycloadditions, 18: 5-Aminoisoxazoles by Cycloaddition of Nitrile Oxides to Ynamines
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Ten differently substituted ynamines 1a-j react with five nitrile oxides 3a-e to give the 5-aminoisoxazoles 4a-z.The stannyl-substituted ynamine 1k furnishes the same compounds (e.g. 4a-d) by reaction with the hydroximoyl chlorides 2a-d.Two representatives of 4 - b and p - can be transformed into the corresponding 1-azirine-3-carboxamides 6a and b.
- Himbert, Gerhard,Kuhn, Hildegard,Barz, Michael
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p. 403 - 407
(2007/10/02)
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- Reduction of Substituted Δ2-Isoxazolines. Synthesis of β-Hydroxy Acid Derivatives
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Three separate methods are reported for the formation of β-hydroxy acid derivatives from readily available substituted Δ2-isoxazolines.Cycloaddition of 2,2-dimethylpropanenitrile oxide with a variety of olefins followed by reductive cleavage produces α '-tert-butyl β-hydroxy ketones.These are cleaved to β-hydroxy tert-butyl esters by Baeyer-Villiger oxidation with peroxytrifluoroacetic acid.In the second approach, α ',β-dihydroxy ketones are generated via cycloaddition of olefins with the nitrile oxide generated from 2--2-methyl-1-nitropropane followed by reductive ring opening.Standard periodic acid cleavage gives β-hydroxy acids.Finally, 3-methoxy-substituted Δ2-isoxazolines, readily available via benzenesulfonylcarbonitrile oxide-olefin cycloaddition and methoxide displacement, are directly reduced to β-hydroxy esters.
- Curran, Dennis P.,Scanga, Susan A.,Fenk, Christopher J.
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p. 3474 - 3478
(2007/10/02)
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