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Nitroaldol reaction

The Nitroaldol reaction or Henry reaction ^[1] is an aldol type reaction between an aldehyde and nitromethane. The nucleophilic addition step is base catalysed and may be followed by an elimination reaction with removal of water when an acidic alpha proton is present. The reaction product is a beta-hydroxy nitro-compound or a nitroethylene compound.

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For example benzaldehyde reacts with nitroethane to trans-1-phenyl-2-methyl-2-nitroethene ^[2]. With ammonium acetate as a catalyst this dry media reaction proceeds with microwave irradiation under 7 minutes.

An enantioselective aldol addition product can be obtained in asymmetric synthesis by reaction of benzaldehyde with nitromethane and the a catalyst system consisting of a zinc triflate salt / the base diisopropylethylamine (DIPEA) and as chiral ligand is the N-methyl derivative of (+)-ephedrine (NME) ^[3].

A diastereoselective variation of this reaction is depicted below ^[4] :

References

^ Henry, L. C. R. Hebd. Acad. Sci. 1895, 120, 1265.
^ Microwave-assisted Henry reaction: Solventless synthesis of conjugated nitroalkenes Rajender S. Varma, Rajender Dahiya, Sudhir Kumar Tetrahedron Letters Volume 38, Issue 29 , 21 July 1997, Pages 5131-5134 Abstract
^ Enantioselective Henry Reactions under Dual Lewis Acid/Amine Catalysis Using Chiral Amino Alcohol Ligands Claudio Palomo, Mikel Oiarbide, Antonio Laso Angewandte Chemie, Volume 44, Issue 25 , Pages 3881 - 3884 2005 Abstract
^ Organocatalyzed diastereoselective Henry reaction of enantiopure 4-oxoazetidine-2-carbaldehydes Benito Alcaide, Pedro Almendros, Amparo Luna, M. Paz de Arriba and M. Rosario Torresc ARKIVOC 2007 (iv) 285-296 Link