Y-Nitroketones

This class was first reported in 1924 and was formed 62HC(17)l) by cyclization of a-bromo-/3-aryl-y-nitroketones. The direct synthesis by oxygenation of 2-isoxazolines has not been reported. To date only 3-substituted derivatives have been prepared. Aryl-nitromethanes react with nitrostilbene to form isoxazoline A-oxide by a nitrile ion displacement (Scheme 138) <62HC(17)1, 68TL3375). 

Valendn and coworkers have studied extensively the reaction of enamines v/ith nltroalkenes. The reaction proceeds under rruld conditions to give y-nitroketones, which are converted into 1,4-diketones by the Nef reaction CEq. 4.65. ... 

The reduction of y-nitroketone acetals as in Eq. 6.50 v/ith ammonium formate in the presence of Pd/C gives the correspondmg amines in good yields. However, the reduction ofy-nitro ketones are reduced to cyclic nitrones fEq. 6.51. This reduction is far superior to the classical method using Zn/T4HlCl due to improved yield and simple workup. 

Redncdons of y-nitroketones yield cyclic nitrones, which undergo inter- and intramolecular cycloadthdon to various alkenes. The result of adthdon to acrylonitrile is shown in Eq. 8.43, in which a rruxnire of regio- and stereoisomers is formed. - ... 

The Michael dclclidon of nitro ilkdnes to a,fi-unsdnirdted ketones gives Y-nitroketones, which re convetted into pyrroles by reduction of the nitro group with and PhSSPh fEq. 10.2. ... 

As a new and practical synthesis of pyrroles, Zard and coworkers have presented the reduction of Y-nitroketones v/ith formamidinesiilfinic acid fEq. IC.Bi/... 

Ruthenium complex catMyzes reducdve iV-heterocyclizadon of y-nitroketones to give pyr-rohne detivadves fEq. 10.72. ... 

Baker s yeast reducdon of y-nitroketones offers the corresponding chiral nitro alcohols, which areusefid bndding blocks for the synthesis of chiral naniral compounds. For example, opdcally acdve 2-subsdnited pyrrolidine can be prepared using the chiral nitro alcohol fEq. 10.751. ... 

In the aliphatic series, hydrogenation of y-nitroketones gives pyrrolidines in good yields (52) and tx-nitroketones give a mixture of pyrazines and piperazines (i5). 

The enantioselective reduction of y-nitroketones and y-nitrodiketones by the chiral reducing agent (+)- or (-)-dusopinocamphenylchloroborane (DIP-C1 ) gives nitro alcohols having from 33 to 86% ee and nitrodiols with complete diastereoselectivity and > 95% ee.122... 

According to the working potential, the medium, and the nature of substituents, the cathodic reduction of aliphatic y-nitroketones leads to pyrroline... 

Allen and Happ85 investigated the thermal reversibility of the Michael adducts. They detected furan derivatives, e.g., triphenyl-and diphenylfuran, in the mass spectra of y-nitroketones ... 

In the aliphatic series, pyrroline Y-oxides [61], Y-hydroxypyrrolidinones, and iso-xazolones [61] may be obtained by reduction of y-nitroketones, y-nitroesters, and y6-nitroamides, respectively. 

Several other ketones were employed as starting material. Pyridazines were obtained from y-nitroketones and hydrazine. The initially formed... 

Several other ketones were employed as starting material. Pyridazines were obtained from y-nitroketones and hydrazine. The initially formed 4,5-dihydro-3(2H)-pyridazinone oximes (4) are transformed with dilute acid into 5.58 The reaction is postulated to proceed via a nitrile oxide, generated from the nitromethyl group. 

Carbonyl reduction. Reduction of a-diketones, a-ketoesters, -ketoesters, and l-acetoxy-2,4-alkanediones in high ee have been reported. y-Nitroketones afford (S)-4-nitro alcohols. ... 

Chiral cyclohexene derivatives were also constructed by an asymmetric four-component quadruple domino reaction initiated by oxa-Michael addition of alcohols to acrolein. The other two components were another equivalent of acrolein and a nitroalkene. Enders has shown that cyclohexene derivatives can also be assembled by a domino reaction of y-nitroketones and enals. Domino Michael/aldol condensation of 5-oxoalkanals and a,p-unsaturated aldehydes afforded densely functionalised cyclohexenes. Combination of unsaturated aldehydes with unsaturated p-ketoesters resulted in the formation of chiral cyclohexene derivatives via a Michael/ Morita-Baylis-Hillman sequence (Scheme 8.21). ... 

A highly enantioselective conjugate addition of nitromethane and nitroethane to acyclic enones has been recently achieved using chiral cyclohexanediamine-derived primary amine thiourea 48 (Scheme 2.57) [168], With respect to the electrophile, the reaction shows a broad substrate scope and not only 1-aryl- but also 1-alkyl enones afford the corresponding chiral y-nitroketones with good yields and excellent enantioselectivities (92-99% ee). 

Enders et al. [54] developed an asymmetric organocatalytic domino reaction of y-nitroketones 83 and enals. The reaction, catalyzed by compound VII, renders the final cyclohexene 84 via a Michael-Aldol cascade reaction followed by dehydration, with moderate yields and diastereoselectivities and good enantioselectivities (Scheme 10.23). Two years later, the same research group reported a related reaction starting from 2-(nitromethyl)benzaldehyde [55]. The reaction proceeds via a domino nitroalkane-Michael-aldol condensation reaction that leads to the final 3,4-dihydronaphthalenes in excellent yields and enantioselectivities. 

Ji.Pyrroline 1-oxides from y-nitroketones s. 17, 553 Palladium-carbon... 

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