Nouvelle voie d'acces aux β-nitroenones premiere preparation de β-nitroenones acycliques
摘要:
We describe here a new and mild method of synthesis of acyclic beta-nitroenones. Nitroepoxydes IVunderbar, prepared by epoxydation of the allylic nitroolefins IIIunderbar, react with silicagel or aluminium isopropoxide according to the substrate, to give the nitroethylenic alcohols Vunderbar. Their oxydation by PCC under sonication leads to the beta-nitroenones VIunderbar.
Abstract β-Dicarbonyl compounds, phenylsulfonylacetate, cyanoacetate and malonitrile sodium enolates add to β-nitroenones at the α-carbon atom of the unsaturated carbonyl system and provide access to highly functionalised intermediates.
A new synthesis of 2-isoxazoline2-oxides starting from unsaturated nitro compounds is described. A facile and convenient preparation of β-alkyl substituted β-nitroenones and their conversion to β-nitrosulfides are recorded. Treatment of these compounds with potassium tert-butoxide at −78°C followed by immediate quenching with acetic acid provides access to 5-hydroxy-4-(phenylthio)-2-isoxazoline 2-oxides
Stereoselectivity of the reaction of acyclic ketone enolates with (E)-β-nitroenones was investigated according to the nature of the base used to accomplish deprotonation. The stereoselectivity and the regioselectivity of the reaction of ketone enolates with (E)-β-nitroenones could be enhanced by the use of trichlorotitanium enolates, which allowed the formation of diastereomeric mixture of (E)-3-h
Under kinetic control at -78 degrees C, reactions of ketone or ester lithium enolates with (E)-beta-nitroenones 2 occurred at the carbonyl group giving (E)-3-hydroxy-5-nitroalk-4-enones 6 or (E)-3-hydroxy-5-nitroalk-4-enoates 13, respectively, with good regioselectivity. When the temperature of the reaction between 2 and lithium ketone enolates was allowed to warm up to -10 degrees C before hydrolysis, solely the 2-(nitromethyl) 1,4-diketones 8 were obtained. Steric factors which might influence the observed stereoselectivities during the nucleophilic attack on beta-nitroenones are discussed.
Schneider, Raphael; Gerardin, Philippe; Loubinoux, Bernard, Journal of Heterocyclic Chemistry, 1994, vol. 31, # 4, p. 797 - 804
作者:Schneider, Raphael、Gerardin, Philippe、Loubinoux, Bernard