- A Sequential Homologation of Alkynes and Aldehydes for Chain Elongation with Optional 13C-Labeling
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Terminal alkynes (RCCH) are homologated by a sequence of ruthenium-catalyzed anti-Markovnikov hydration of alkyne to aldehyde (RCH2CHO), followed by Bestmann-Ohira alkynylation of aldehyde to chain-elongated alkyne (RCH2CCH). Inverting the sequence by starting from aldehyde brings about the reciprocal homologation of aldehydes instead. The use of 13C-labeled Bestmann-Ohira reagent (dimethyl ((1-13C)-1-diazo-2-oxopropyl)phosphonate) for alkynylation provides straightforward access to singly or, through additional homologation, multiply 13C-labeled alkynes. The labeled alkynes serve as synthetic platform for accessing a multitude of specifically 13C-labeled products. Terminal alkynes with one or two 13C-labels in the alkyne unit have been submitted to alkyne-azide click reactions; the copper-catalyzed version (CuAAC) was found to display a regioselectivity of >50 000:1 for the 1,4- over the 1,5-triazine isomer, as shown analytically by 13C NMR spectroscopy.
- Brunner, Andreas,Hintermann, Lukas
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p. 2787 - 2792
(2016/02/27)
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- Chemoselectivities in the platinum-catalyzed hydrative carbocyclizations of oxo-alkyne-nitrile functionalities
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Two new hydrative carbocyclizations of oxa-alkyne-nitrile functionalities are reported to produce distinct nitrogen-containing heterocycles. Protracted heating of oxoalkynyl nitrile substrates with PtCl2/CO/H2O in hot 1,4-dioxane gave 2,3-dihydro-1H-pyrido[1.2-b]-isoquinolin-4(6H)-ones. In this hydration reaction, dicarbonyl nitrile intermediates were isolated efficiently after a brief period, and they were subjected to an NHC-based crossed benzoin coupling to give spiro alcohols that further reacted with TfOH to give spiro[indene-2,2′-piperidine]-1,6′(3H)-diones.
- Mukherjee, Anupam,Liu, Rai-Shung
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supporting information; experimental part
p. 660 - 663
(2011/05/03)
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- Nitrone dipolar cycloaddition routes to piperidines and indolizidines. Part 9. Formal synthesis of (-)-pinidine and total synthesis of (-)-histrionicotoxin, (+)-histrionicotoxin and (-)-histrionicotoxin 235A
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An intramolecular hydroxylamine-alkyne cyclisation is used for the enantioselective synthesis of the cyclic nitrones 36 and 44. We have demonstrated the use of a novel nitrone protection strategy by cycloaddition of styrene to the cyclic nitrone 44 in the synthesis of the spirocyclic core of the histrionicotoxin family of alkaloids. Deprotection by dipolar cycloreversion of the styrene adduct (the bicyclic isoxazolidine 39) and in situ intramolecular dipolar cycloaddition of a pendant (Z)-α,β-unsaturated nitrile to the intermediate nitrone 50 gave the isoxazolidine 51 in high yield with a surprising degree of regioselectivity compared with the corresponding (Z)-enyne 36. The method is amenable to the synthesis of both enantiomers 51 and 62 of the tricyclic core structure which can be converted by way of the common intermediates (e.g. 53 and ent-53) respectively into the natural configuration of alkaloids (-)-histrionicotoxin 1 and (-)-histrionicotoxin 235A 65 as well as the unnatural (+)-histrionicotoxin 63.
- Davison, Edwin C.,Fox, Martin E.,Holmes, Andrew B.,Roughley, Stephen D.,Smith, Catherine J.,Williams, Geoffrey M.,Davies, John E.,Raithby, Paul R.,Adams, Joseph P.,Forbes, Ian T.,Press, Neil J.,Thompson, Mervyn J.
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p. 1494 - 1514
(2007/10/03)
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- UROKINASE INHIBITORS
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Disclosed are benzothiophene and thienothiophene derivatives useful for inhibiting urokinase activity.
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- Pesticidal compounds
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The present invention provides a class of novel substituted bicyclooctanes which have pesticidal activity, particularly against arthropod pests. Pesticidal formulations containing the compounds of the formula (I), their use in the control of pests and methods for their preparation are also disclosed.
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- Intramolecular Diels-Alder Reactions of 1,2,4-Triazines. Synthesis of 2,3-Cyclopentenopyridines and 5,6,7,8-Tetrahydroquinolines
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2,3-Cyclopentenopyridines and 5,6,7,8-tetrahydroquinolines are prepared by intramolecular Diels-Alder reactions of appropriately substituted 1,2,4-triazines.Two general routes to the requisite triazine precursors are described.
- Taylor, Edward C.,Macor, John E.,French, Larry G.
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p. 1807 - 1812
(2007/10/02)
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- Pesticidal compounds
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The present invention provides compounds of the formula (I): STR1 wherein R is a C2-10 non-aromatic hydrocarbyl group, a C2-10 non-aromatic hydrocarbyl group substituted by, or methyl substituted by cyano, halo, C1-4 alkox
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- Intramolecular Cycloadditions of Mesionic Carbonyl Ylides with Alkynes. Synthesis of 5,6-Dihydro-4H-cyclopenta- and 4,5,6,7-Tetrahydrobenzofuran Derivatives
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Intramolecular cycloaddition reactions of acetylenic isomuenchnones, formed in situ by rhodium acetate catalyzed decomposition of N-(diazoacetyl)-N-methylalkynamide derivatives 16a-c, 18c, and 18d have been studied.The intermediate cycloadducts fragmentate spontaneously under the reaction conditions (110 deg C) to afford the annulated furans 19a-c, 20c, and 20d. - Keywords: Carbonyl ylides; Furans; Intramolecular cycloadditions; Isomuenchnones
- Maier, Martin E.,Schoeffling, Baerbel
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p. 1081 - 1088
(2007/10/02)
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- Oxidized Leukotrienes: Synthesis of 20-OH and 20-COOH LTD4. Possible Metabolites in the Lipoxygenase Pathway
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Leukotriene LTD4 analogs 20-OH LTD4 16 and 20-COOH LTD4 17 were synthesized.These ω-oxidative derivatives are possible metabolites of the natural product.
- Adams, Julian,Milette, Suzanne,Rokach, Joshua,Zamboni, Robert
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p. 2179 - 2182
(2007/10/02)
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