Conjugate Addition Of Nitroalkanes Research Articles

Copper-Catalyzed Asymmetric Conjugate Addition of Nitroalkanes

Copper-Catalyzed Asymmetric Conjugate Addition of Nitroalkanes

Regioselectivity in Intermolecular Pauson-Khand Reactions of Dissymmetric Fluorinated Alkynes

Stoichiometric and catalytic intermolecular Pauson-Khand reactions (PKRs) of dissymmetric fluorinated alkynes were performed, affording regioselectively α-fluorinated cyclopentenones. Ethyl 4,4,4-trifluorobutynoate was an excellent substrate; its reaction with norbornadiene gave the corresponding PKR adduct in good yield and complete regioselectivity. Conjugate addition of nitroalkanes or cyanide to this adduct is stereospecific and entails concomitant loss of a trifluoromethyl group. This reaction can be exploited to prepare cyclopentenones featuring quaternary centers.

Organocatalytic conjugate addition of nitroalkanes to 2H-chromene-3-carbaldehydes: synthesis of highly functionalized chroman derivatives

Conjugate addition of nitroalkanes to 2H-chromene-3-carbaldehydes has been studied using a number of amines as the catalysts. Prolinol triethylsilyl ether was found to be the best catalyst for the reaction. The use of protonic solvents was also important. The reaction of variously substituted 2H-chromene-3-carbaldehydes with nitromethane afforded the products with excellent yields and diastereoselectivities. Nitroethane and 1-nitropropane were also applicable, however in decreased yields. The enantioselectivities of the reaction were very low and almost racemic products (3~5% ee) were obtained in all cases. The reaction provides a new method for the preparation of highly functionalized chroman derivatives.

Catalytic Asymmetric Conjugate Addition of Nitroalkanes to 4-Nitro-5-styrylisoxazoles

Catalytic Asymmetric Conjugate Addition of Nitroalkanes to 4-Nitro-5-styrylisoxazoles

Conjugate Addition of Nitroalkanes to Vinyl Sulfone

Conjugate Addition of Nitroalkanes to Vinyl Sulfone

New liquid crystalline compounds based on 2-arylthiophenes and 2-(biphenyl-4-yl)thiophenes

Abstract A general and versatile route to the 2-alkyl-5-(4′-cyanophenyl)thiophenes was established, involving the condensation of an aryl vinyl ketone with an aldehyde in the presence of a thiazolium catalyst (Stetter procedure) to give a 1,4-diketone which with Lawesson's reagent undergoes ring-closure to give the corresponding arylthiophene. In the final step the exchange of a bromo substituent on the phenyl ring for a cyano group is accomplished by copper(I) cyanide in N,N-dimethylforamamide at reflux. The same sequence afforded 2-alkyl-5-(4″-cyanobiphenylyl)thiophenes. Several of the 1,4-diketones were obtained by conjugate addition of nitroalkanes to aryl vinyl ketones, and treatment of the γ-nitroketones with silica gel-supported potassium permanganate. Three alkyl 5-(4-cyanophenyl)thiophene-2-carboxylates were prepared by condensing β-chlorovinylaldehydes with thioglycolates. The cyanophenylthiophenes exhibited only monotropic phases, but incorporation of an additional phenyl ring provided cyanobip...

ChemInform Abstract: The Nef Reaction

The Nef reaction is usually defined as the conversion of a primary or secondary nitroalkane into the corresponding carbonyl compound. This reaction was reported by the Swiss chemist J. U. Nef in 1894. Hydrochloric and sulfuric acid give the same result. The conversion of a nitro group to a carbonyl group has become an important synthetic tool because of the ease of preparation of substituted nitro compounds by condensation of nitroalkanes with aldehydes (the Henry reaction), conjugate addition of nitroalkanes to electrophilic alkenes, or carbon alkylation of the dianion of primary nitroparaffins. The Nef reaction is one of the better examples of “umpolung” reactivity in which the original nitro compound anion functions as an acyl anion equivalent. This chapter discusses the Nef reaction and modifications of the original process that extend the variety of compounds which are useful as substrates. Each modification is considered according to general mechanistic type and is organized in a “reagent” approach. The Tabular Survey lists all known examples of both the Nef reaction and these modifications so that specific comparison of methods can be made. Keywords: Nef reaction; scope; limitations; oxidizing agents; reducing agents; nitro compounds; alkylation; acylation; nitroolfins; nitroepoxides; experimental procedures; nitronates; side reactions; synthetic utility

Conjugate addition to 5-phenylsulfinyl 2-substituted 2-cyclopentenones: A new route to 4,5-disubstituted 2-cyclopentenones

4,5-Disubstituted 2-cyclopentenones have been prepared by conjugate addition of nitroalkanes and of organocopper reagents to 5-phenylsulfinyl 2-substituted 2-cyclopentenones, followed by pyrolysis.

Utilization of Basic Alumina in a One-Pot Synthesis of 1,4-Diketones, 1,4,7-Triketones, and Dihydrojasmone by Conjugate Addition of Nitroalkanes to Enones

Utilization of Basic Alumina in a One-Pot Synthesis of 1,4-Diketones, 1,4,7-Triketones, and Dihydrojasmone by Conjugate Addition of Nitroalkanes to Enones