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