Nitroaldols Henry reaction

Gruber-Khadjawi, M., Purkarthofer, T. Skranc, W. et al. (2007) Hydroxynitrile lyase-catalyzed enzymatic nitroaldol (Henry) reaction. Advanced Synthesis and Catalysis, 349, 1445-1450. 

The nitroaldol (Henry) reaction has been recognized as a powerful synthetic tool and has also been utilized in the construction of numerous natural products and other useful compounds. As shown in Scheme 1, we succeeded in realizing the first exam-... 

Nitroaldol (Henry) reaction of nitro alkanes with sugar aldehydes... 

Palomo, C. Oiarbide, M. Mielgo, A. Unveiling reliable catalysts for the asymmetric nitroaldol (Henry) reaction. Angew. Chem. Int. Ed. 2004,43,5442-5444. 

The nitroaldol (Henry) reaction constitutes a powerful C-C bond-forming process in organic chemistry, providing efficient access to valuable functionalized organic compounds such as 1,2-amino-alcohols, a-hydroxy-carboxylic acids and 3-hydroxy-nitroalkanes [215, 216]. 

Scheme 12.22 Asymmetric nitroaldol (Henry) reaction of various aldehydes (Pe-h) with nitromethane.

Nitroaldol (Henry) reactions of nitroalkanes and a carbonyl were investigated by Hiemstra [76], Based on their earlier studies with Cinchona alkaloid derived catalysts, they were able to achieve moderate enantioselectivities between aromatic aldehydes and nitromethane. Until then, organocatalyzed nitroaldol reactions displayed poor selectivities. Based on prior reports by Sods [77], an activated thionrea tethered to a Cinchona alkaloid at the quinoline position seemed like a good catalyst candidate. Hiemstra incorporated that same moiety to their catalyst. Snbsequently, catalyst 121 was used in the nitroaldol reaction of aromatic aldehydes to generate P-amino alcohols in high yield and high enantioselectivities (Scheme 27). 

Simoni, D., Rondanin, R., Morini, M., Baruchello, R. and Invidiata, F.P., 1,5,7-triazabicyclo 4.4.0 dec-l-ene (TBD), 7-methyl-TBD (MTBD) and the polymer-supported TBD (P-TBD) three efficient catalysts for the nitroaldol (Henry) reaction and for the addition of dialkyl phosphites to unsaturated systems, Tetrahedron Lett., 2000, 41, 1607. 

The nitroaldol (Henry) reaction, first described in 1859, is a carbon-carbon bondforming reaction between an aldehyde or ketone and a nitroalkane, leading to a nitroalcohol adduct [29]. The nitroalcohol compounds, synthetically versatile functionalized structural motifs, can be transformed to many important functional groups, such as 1,2-amino alcohols and a-hydroxy carboxylic acids, common in chemical and biological structures [18, 20, 30, 31]. Because of their important structural transformations, new synthetic routes using transition metal catalysis and enzyme-catalyzed reactions have been developed to prepare enantiomerically pure nitroaldol adducts [32-34]. 

After the reaction reached completion, the solid product was filtered off and identified by NMR spectroscopy and X-ray crystallography. By analyzing the data, the unexpected formation of amide product 40 from benzaldehyde 37C and its corresponding intermediate 39C was revealed. This represented a new transformation pathway, for which only a few related systems have been reported [58-60]. Scheme 14 displays the proposed mechanistic formation of amide product 40, supported by density functional theory (DFT) calculations [61]. In the presence of triethylamine as catalyst, the key intermediate 39C was formed from nitroaldol (Henry) reaction of 2-cyanobenzaldehyde 37C and nitroethane 38. The nitroaldol adduct 39C then underwent internal cyclization (5-exo-dig) to give iminolactone 41,... 

Vongvilai P, Larsson R, Ramstrom O (2008) Direct asymmetric dynamic kinetic resolution by combined lipase catalysis and nitroaldol (Henry) reaction. Adv Synth Catal 350 448 152... 

NITROALKANES AS BUILDING BLOCKS FOR ONE-POT PROCESSES, VIA NITROALDOL (HENRY) REACTION... 

The latter compounds are prone to an intramolecular nitroaldol (Henry) reaction, yielding nitrocyclohexanola (53) in less than 1 h. The formation of (53) can be easily observed by thin-layer chromatography (TLC), thus treatment of (53) with 4N hydrochloric acid favors the elimination of both water and a further molecule of nitrous acid, allowing the one-pot synthesis of target molecules (54) in 42-77% overall yields. It is important to note that this one-pot process formally includes five different transformations (i) Michael addition, (ii) nitrous acid elimination, (iii) intramolecular nitroaldol reaction, (iv) water elimination, and (v) elimination of a further molecule of nitrous acid. 

Nitroalkanes are the key starting precursors for the formation of C-C bond by reactions with aldehydes (nitroaldol-Henry reaction) and electron-poor alkenes (Michael... 

Morao, I., Cossio, F. P. Dendritic catalysts forthe nitroaldol (Henry) reaction. Tetrahedron Lett. 1997, 38, 6461-6464. 

Condensation reactions. The triisopropyl base is an efficient promoter for the nitroaldol (Henry) reaction, and condensation between alkanonitriles and carbonyl compounds. ... 

Aryl ether dendrimer 419" [GO] 2.4" [GO] Nitroalkane Nitroaldol (Henry) reaction (-) Flash chromato- [126]... 

In their extensive efforts to devise a new strong nonionic base, Verkade and coworkers found that a highly basic dendrimer containing a PAPT base fragment could act as an efficient catalyst for Michael addition reactions, nitroaldol (Henry) reactions and aryl isocyanate trimerization reactions [42] (Figure 6.3). In view of the characteristic nature of this dendrimer, which has sixteen catalytic sites per molecule, the attachment of other superbase functionalities might also be attractive. 

Recent advances in the catalytic asymmetric nitroaldol (Henry) reaction including application of heterocyclic organocatalysis and hgands 07EJO2561. 

The nitroaldol (Henry) reaction involves the addition of nitronates to aldehydes and ketones to give a P-nitroalcohol. These products are usefrd synthetic building blocks as the nitro group can be transformed into a range of other functional groups, and this has stimulated some recent research into the development of a catalytic asymmetric variant. Some of the catalyst systems used in the asymmetric aldol rection have been successfully employed in the catalytic asymmetric nitroaldol process. 

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