Nitro addition compounds with ketones

These reversible reactions are cataly2ed by bases or acids, such as 2iac chloride and aluminum isopropoxide, or by anion-exchange resias. Ultrasonic vibrations improve the reaction rate and yield. Reaction of aromatic aldehydes or ketones with nitroparaffins yields either the nitro alcohol or the nitro olefin, depending on the catalyst. Conjugated unsaturated aldehydes or ketones and nitroparaffins (Michael addition) yield nitro-substituted carbonyl compounds rather than nitro alcohols. Condensation with keto esters gives the substituted nitro alcohols (37) keto aldehydes react preferentially at the aldehyde function. 

The conjugate addition of heteronucleophiles to activated alkenes has been used very often in organic synthesis to prepare compounds with heteroatoms [3 to various activating functional groups, e.g. ketones, esters, nitriles, sulfones, sulfoxides and nitro groups. As in the Michael reaction, a catalytic amount of a weak base is usually used in these reactions (with amines as nucleophiles, no additional base is added). 

Acceptor-substituted alkenes that are employed as substrates in Michael additions include a./l-unsaturated ketones (for example, see Figure 10.59), a,/3-unsaturated esters (Figure 10.60), and a,/3-unsaturatcd nitriles (Figure 10.61). The corresponding reaction products are bifunctional compounds with C=0 and/or C=N bonds in positions 1 and 5. Analogous reaction conditions allow Michael additions to vinyl sulfones or nitroalkenes. These reactions lead to sulfones and nitro compounds that carry a C=0 and/or a O N bond at the C4 carbon. 

Ni(II)(OAc)2bpy and Co(II)(OAc)2bpy catalyze the Michael addition of nitro-methane, malononitrile, and aniline to a,j8-unsaturated ketones, methyl acrylate, and acrylonitrile in DMF under neutral conditions [116]. FeCls 6H2O is a highly efficient catalyst of Michael reaction of 1,3-dicarbonyl compounds with a,/3-unsaturated ketones under mild and neutral conditions (Sch. 24) [117]. There is literature precedent for this reaction with dual catalysis Ni(II) immobilized on a clay support and FeCl3 to activate the enone [118]. The mechanism proposed for the single-center catalysis involves coordination of the enone to a diketonato complex [119]. The chemo-... 

The a-hydrogens of nitroalkanes are appreciably acidic due to resonance stabilization of the anion [CH3NO2, 10.2 CH3CH2NO2, 8.5]. The anions derived from nitroalkanes give typical nucleophilic addition reactions with aldehydes (the Henry-Nef tandem reaction). Note that the nitro group can be changed directly to a carbonyl group via the Nef reaction (acidic conditions). Under basic conditions, salts of secondary nitro compounds are converted into ketones by the pyridine-HMPA complex of molybdenum (VI) peroxide. Nitronates from primary nitro compounds yield carboxylic acids since the initially formed aldehyde is rapidly oxidized under the reaction conditions. 

Michael addition of the (S nitroester 95 to the unsaturated ketone 96 gave a mixture of 97 and the (22S)-isomer (207, 208). Sodium borohydride reduction of 97 in an acidic medium afforded the nitrodiol 98 in excellent yield. Reduction of the nitro group and subsequent lactam formation (99) proceeded smoothly when the nitrodiol 96 was refluxed with zinc and acetic acid. Further reduction of the amide 99 with LAH yielded the piperidine 100, which was converted into its iV-chloro derivative. Treatment of this compound with sodium methoxide effected dehydrochlorination which was... 

Michael addition with -acoxyketones. 2-Ni-tropropane and Na-acetate added at 0-5° to a soln. of NaOH in methanol-water, after salt formation is complete 3-ketobutyl acetate added dr op wise during 15 min., and kept 20 hrs. at 40-45° 5-methyl-5-nitro-2-hexanone. Y 92%.—3-Ketobutyl acetate, the precursor of methyl vinyl ketone, is quite stable toward polymerization and can be stored readily at room temp. F. Michael additions, also with 2-acoxy-nitro compounds, s. J. Org. Ghem. 26, 1348. 

The two major methods of preparation are the cycloaddition of nitrile oxides to alkenes and the reaction of a,/3-unsaturated ketones with hydroxylamines. Additional methods include reaction of /3-haloketones and hydroxylamine, the reaction of ylides with nitrile oxides by activation of alkyl nitro compounds from isoxazoline AT-oxides (methoxides, etc.) and miscellaneous syntheses (62HC(i7)i). 

Nitro functions are easily reductively alkylated and a number of alkylated anilines are made industrially starting with the appropriate nitroaromatic in the ketone as solvent. The addition reaction can occur at the hydroxylamine intermediate as well as the aniline. A process step is saved by beginning with the nitro compound. 

Recently, Dutta and Maiti [21] reported nitro displacement polymerization of the bisphenol dianion with the sulfone activated dinitro aromatic compounds. In addition, there have been recent reports of the development of functionalized PEEK [22] and polyether sulfone ketone (PESK) [23] that are comparable to commercially available high performance polymers. 

The base-catalysed reaction of a-bromo-a,P-unsaturated ketones with aliphatic nitro compounds leads to 2-isoxazoline A-oxides by tandem conjugate addition-ring closure (Scheme 5) <95JOC6624>. A -Acyl-3-isoxazolin-5-ones are transformed into oxazoles by photolysis or by flash vacuum pyrolysis (Scheme 6) <96TL675>. 

The addition reaction of enolates and enols with carbonyl compounds is of broad scope and of great synthetic importance. Essentially all of the stabilized carbanions mentioned in Section 1.1 are capable of adding to carbonyl groups, in what is known as the generalized aldol reaction. Enolates of aldehydes, ketones, esters, and amides, the carbanions of nitriles and nitro compounds, as well as phosphoms- and sulfur-stabilized carbanions and ylides undergo this reaction. In the next section we emphasize the fundamental regiochemical and stereochemical aspects of the reactions of ketones and aldehydes. 

The conversion of primary or secondary nitro compounds into aldehydes or ketones is normally accomplished by use of the Nef reaction, which is one of the most important transformations of nitro compounds. Various methods have been introduced forthis transformation (1) treatment of nitronates with acid, (2) oxidation of nitronates, and (3) reduction of nitroalkenes. Although a comprehensive review is available,3 important procedures and improved methods published after this review are presented in this chapter. The Nef reaction after the nitro-aldol (Henry reaction), Michael addition, or Diels-Alder reaction using nitroalkanes or nitroalkenes has been used extensively in organic synthesis of various substrates, including complicated natural products. Some of them are presented in this chapter other examples are presented in the chapters discussing the Henry reaction (Chapter 3), Michael addition (Chapter 4), and Diels-Alder reaction (Chapter 8). 

The starting aUylic nitro compound is obtained by nitration of 2-methylpropene with NOz. Subsequent Michael addition to methyl vinyl ketone followed by Pd-cataly zed ally lie alkylation affords terpenoids. 

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