Michael addition reaction nitro

Chiral secondary amines are another important class of privileged functional component in dual organocatalysis that has been widely used in asymmetric catalysis [39]. For example, in 2008, Cordova et al. [40] reported the combinational use of (S)-diphenylprolinol TMS ether (127) and Br0nsted base DABCO (128) as dual organocatalysts to promote the asymmetric domino double Michael addition reaction (nitro-Michael/Michael reaction) of 5-nitropentenoate (125) to a,(i-unsaturated aldehydes (Scheme 43.26), which gave the corresponding nitrogen-,... 

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. 

Purines, N-alkyl-N-phenyl-synthesis, 5, 576 Purines, alkylthio-hydrolysis, 5, 560 Mannich reaction, 5, 536 Michael addition reactions, 5, 536 Purines, S-alkylthio-hydrolysis, 5, 560 Purines, amino-alkylation, 5, 530, 551 IR spectra, 5, 518 reactions, 5, 551-553 with diazonium ions, 5, 538 reduction, 5, 541 UV spectra, 5, 517 Purines, N-amino-synthesis, 5, 595 Purines, aminohydroxy-hydrogenation, 5, 555 reactions, 5, 555 Purines, aminooxo-reactions, 5, 557 thiation, 5, 557 Purines, bromo-synthesis, 5, 557 Purines, chloro-synthesis, 5, 573 Purines, cyano-reactions, 5, 550 Purines, dialkoxy-rearrangement, 5, 558 Purines, diazoreactions, 5, 96 Purines, dioxo-alkylation, 5, 532 Purines, N-glycosyl-, 5, 536 Purines, halo-N-alkylation, 5, 529 hydrogenolysis, 5, 562 reactions, 5, 561-562, 564 with alkoxides, 5, 563 synthesis, 5, 556 Purines, hydrazino-reactions, 5, 553 Purines, hydroxyamino-reactions, 5, 556 Purines, 8-lithiotrimethylsilyl-nucleosides alkylation, 5, 537 Purines, N-methyl-magnetic circular dichroism, 5, 523 Purines, methylthio-bromination, 5, 559 Purines, nitro-reactions, 5, 550, 551 Purines, oxo-alkylation, 5, 532 amination, 5, 557 dipole moments, 5, 522 H NMR, 5, 512 pJfa, 5, 524 reactions, 5, 556-557 with diazonium ions, 5, 538 reduction, 5, 541 thiation, 5, 557 Purines, oxohydro-IR spectra, 5, 518 Purines, selenoxo-synthesis, 5, 597 Purines, thio-acylation, 5, 559 alkylation, 5, 559 Purines, thioxo-acetylation, 5, 559... 

The Michael addition of nitro ilkanes to enones followed by reaction with TiCT provides an excellent route to 1,4-diketones and hence to cyclopentenones. For example, cii -jasmone is readily obtained," as shown in Eq. 6.18. 

The only acyl anion (6) equivalents we have met which will carry out Michael additions are nitro compounds (p Tig3 and 213) but the scales arc weighted against such a Michael reaction as the most hindered atom must be attacked. 

The Michael addition of nitro compounds is a useful method for the preparation of various natural products. The Michael addition of nitroalkanes to dehydroalanines gives y-nitro-a-amino acids, which provides a convenient synthesis of side-chain modified a-amino acids (Eq. 4.114).152 Transformations of y-nitro-a-amino acid derivatives into a-amino acids occur by reductive denitration (see Section 7.2) into y-oxygenated a-amino acids by the Nef reaction (Eq. 

Ballini and coworkers have used the Michael addition of nitro compounds followed by the Nef reaction for the synthesis of various spiroketalic pheromones (Scheme 4.21).159... 

Double Michael additions of nitro compounds bearing tethered acidic carbons to 3-butyn-2-one under NaH catalysis give nitrocyclohexanes with high stereoselectivity. The products are transformed into traws-fused bicyclic compounds via the Dickmann reaction on treatment with base. (Eq.4.129).176... 

Because reductive cleavage of aliphatic nitro compounds with Bu3SnH proceeds via alkyl radicals, nitro compounds are also used as precursors to alkyl radicals. Reactions using nitro compounds may have some advantages over other ones, since aliphatic nitro compounds are available from various sources. For example, the sequence of the Michael additions of nitro compounds provides an excellent method for the construction of quaternary carbon compounds (Eq. 7.79).126 Newkome has used this strategy for the construction of dendritic polymers (Eq. 7.80).127... 

Ono and coworkers have extended the radical elimination of v/c-dinitro compounds to P-nitro sulfones151 and P-nitro sulfides.138,152 As P-nitro sulfides are readily prepared by the Michael addition of thiols to nitroalkenes, radical elimination of P-nitrosulfides provides a useful method for olefin synthesis. For example, cyclohexanone is converted into allyl alcohol by the reaction shown in Eq. 7.110. Treatment of cyclohexanone with a mixture of nitromethane, PhSH, 35%-HCHO, TMG (0.1 equiv) in acetonitrile gives ahydroxymethylated-P-nitro sulfide in 68% yield, which is converted into the corresponding allyl alcohol in 86% yield by the reaction with Bu3SnH.138 Nitro-aldol and the Michael addition reactions take place sequentially to give the required P-nitro sulfides in one pot. 

X,P-Dehydro-a-amino acids are prepared by elimination of HN02 from P-nitro-a-amino acids, which are prepared by reaction of a-bromoglycine derivatives with alkyl nitronates (see Eq. 7.135).181 This process is a new type of the Michael addition of nitro compounds followed by elimination of HNOz. Such unusual amino acids are interesting as enzyme inhibitors.182... 

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 Michael addition reaction is commonly recognized as one of the most important carbon-carbon bond-forming reactions in organic synthesis, and major efforts have been made to develop efficient catalytic systems for this type of transformation. In particular, the Michael addition of a carbon nucleophile to nitroalkenes is a useful synthetic method for the preparation of nitroalkanes [76], which are versatile synthetic intermediates owing to the various possible easy transformations of the nitro group into other useful functional groups, such as amino groups and nitrile oxides. 

Excellent enantioselectivities for all of these dendrimers were observed in the Michael addition reactions of isovaleraldehyde with nitrostyrene. For example, in the presence of 10mol% of the first-generation catalyst, the addition product 2-isopropyl-4-nitro-3-phenyl-butyraldehyde was isolated in 86% yield with 99% ee and moderate diastereoselectivity (diastereomeric ratio (dr) 80 20). Higher diaste-reoselectivities were observed when the meta-substituted dendrimer catalysts were used, but the yields and enantioselectivities were relatively low. In addition, the second-generation dendrimer catalyst could be easily recovered via precipitahon with methanol and reused at least five times, with only a slight loss of catalytic activity. 

Aliphatic nitro compounds serve as good acyl anion equivalents. After electrophilic alkylation at the a-carbon atom, they can be converted into carbonyl compounds by the Nef reaction or by reductive hydrolysis with titanium(III) chloride. The a-nitro carbanions serve as excellent donors in Michael addition reactions with a, -unsaturated systems and therefore the sequence of Michael addition followed by reductive hydrolysis of the nitro group provides a good route to 1,4-dicarbonyl compounds. ds-Jasmone, for example, was readily obtained by using this strategy (1.111). 

Importantly, prolinamide catalysts (Figure 6.3) work well in Michael addition reactions using nitro-olefins as acceptors. iV-Tritylprolinamide 33 and aminonaphthyridine-derived ProNap 34 served as organocatalysts in asymmetric Michael additions of aldehydes and cyclohexanone to nitro-alkenes. Proline-functionalised C3-symmetric 1,3,5-triallq lbenzene 35 was screened in the reaction of cyclohexanone to nitrostyrene to afford the Michael adducts in good yields and diastereoselectivity but low enantioselectivity. 

Scheme 13.19 Proposed mechanism of nitro-Michael addition reactions catalysed by N-terminal primary amino dipeptides.

Subsequently, with the newly developed sterically bulky chiral triazolium salt precatalyst, the Rovis group disclosed a homoenolate Michael addition reaction of enals to nitroalkenes that delivers complementary syw stereoselectivity and allows coupling with aliphatic nitroalkenes. Bulky substituents in the ortho ortho position of the Al-aryl ring of the NHC are crucial for the success of this reaction as it would shift product distribution toward the desired nitro ester by partially bloeking the aeyl anion position (Scheme 7.64). 

Baker, L. M., P. R. Baker, F. Golin-BiseUo et al. 2007. Nitro-fatty acid reaction with glutathione and cysteine. Kinetic analysis of thiol alkylation by a Michael addition reaction. J Biol Ghent 282 (42) 31085-93. 

The Michael addition reactions of nitro compounds such as nitromethane to CF3-containing acrylates such as ethyl (E)-ethyl 3-(trifluoromethyl)acrylate using a microflow reactor (channel width 100 pm, depth ca. 40 pm and length 80 mm flow rate 1 pi min ) has been reported. The reactions proceed smoothly in the presence of DBU as a base to afford the corresponding Michael adducts without any detectable formation of polymeric byproducts (Table 5.3) [11]. 

Polysubstituted 3,4-dihydro-3-nitro-2ff-chromans are obtained from the enantioselective Michael—Michael cascade reaction of chalcone enolates and nitromethane catalyzed by bifunctional thiourea 19 (Scheme 31) (13JOC6488) and tandem Friedel—Crafts alkylation—Michael addition reaction of nitroolefin enoates and 1-methylindole promoted by Zn(OTf)2 (13S601).A squaramide-tertiary amine catalyst promotes the asymmetric sulfa-Michael—Michael cascade reaction of thiosalicylates with nitroalkene enoates which leads to polysubstituted chromans in high yields with excellent stereoselectivities (13OL1190). 

In another one-pot reaction, chiral isoxazoline-fused benzazepines 31 were formed from the reaction of P-nitrostyrene derivatives 30 and 1,3-dicarbonyl species such as dimethyl malonate. The first step is a nitro-Michael addition reaction between the nitro olefin and dimethyl malonate catalyzed by a chiral thiourea organocatalyst, followed by addition of DMAP and Boc anhydride with heating to promote nitrile... 

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