Michael addition reviews

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). 

Deprotection of 2,2-disubstituted-l,3-dithiolanes to give carbonyl compounds can be achieved using Oxone with KBr in aq. MeCN <06TL8559> and a review of silylated heterocycles as formyl anion equivalents includes reference to 64 <06CC4881>. A method for transformation of propargylic dithiolanes 43 into tetrasubstituted furans has been reported <06SL1209> and Michael addition of enolates to the chiral dithiolane dioxide 65 takes place... 

A diverse group of organic reactions catalyzed by montmorillonite has been described and some reviews on this subject have been published.19 Examples of those transformations include addition reactions, such as Michael addition of thiols to y./bunsatu rated carbonyl compounds 20 electrophilic aromatic substitutions,19c nucleophilic substitution of alcohols,21 acetal synthesis196 22 and deprotection,23 cyclizations,19b c isomerizations, and rearrangements.196 24... 

Michael additions to benzotriazole-stabilized carbanions have been reviewed. review of the structural dependence of heterolytic bond dissociation energy of carbon-carbon a-bonds in hydrocarbons has summarized the synthesis and behaviour of molecules in which highly stable cationic and anionic hydrocarbon moieties have apparently been combined. 

During the coverage period of this chapter, reviews have appeared on the following topics reactions of electrophiles with polyfluorinated alkenes, the mechanisms of intramolecular hydroacylation and hydrosilylation, Prins reaction (reviewed and redefined), synthesis of esters of /3-amino acids by Michael addition of amines and metal amides to esters of a,/3-unsaturated carboxylic acids," the 1,4-addition of benzotriazole-stabilized carbanions to Michael acceptors, control of asymmetry in Michael additions via the use of nucleophiles bearing chiral centres, a-unsaturated systems with the chirality at the y-position, and the presence of chiral ligands or other chiral mediators, syntheses of carbo- and hetero-cyclic compounds via Michael addition of enolates and activated phenols, respectively, to o ,jS-unsaturated nitriles, and transition metal catalysis of the Michael addition of 1,3-dicarbonyl compounds. ... 

Some examples of the Michael reaction on the exocyclic double bond of an unsaturated oxazolone have been discussed in previous sections. The synthesis of unsaturated 5(4//)-oxazolones from unsaturated 5(4/l/)-oxazolones via an addition-elimination sequence and the sequential reaction of unsaturated 5(4/i/)-oxazolones with a l,3-bis(nucleophile) have already been considered. This section will review Michael additions exclusively and, in this respect, a wide array of nucleophiles has been studied. 

Classical organic reactions that have been carried out in water include, among others, the Diels-Alder reaction, the Claisen rearrangement, aldol condensations, Michael additions, and nucleophilic substitutions. In the Diels-Alder reaction, for example, water has been found to increase the reaction rate and to enhance the endoselectivity 120). Two reviews summarize the results for organic reactions in water 121). 

Other synthetic approaches via sulfones make use of the Michael addition and cycloaddition to vinyl sulfones (see [401] and [402] for reviews on vinyl sulfones as dienophiles and Michael acceptors). The... 

Exercise 24-20 Show how the following compounds can be prepared from the commercially available nitroalkanes obtained from the nitration of propane. (It may be desirable to review the material on aldol and Michael additions in Chapters 17 and 18.)... 

Review SL 369 (1993) (intramolecular Michael and anti-Michael additions to carbon-carbon triple... 

Reports of other Michael additions that resulted in only modest selectivities (40-50% ee) [24f,24h,24i,46] and earlier studies—especially those from the Wynberg and Colonna groups—of mechanistic or catalyst interest [47,48] are noted. Michael additions have been reviewed [5g]. 

For recent and general reviews on catalytic asymmetric Michael additions, see (a) N. Krause, A. Hoffmann-Roder, Synthesis 2001, 171-196 (b) M. P. Sibi, S. Manyem, Tetrahedron 2000, 56, 8033-8061. 

Review. Davies has reviewed use of the chiral iron auxiliary [CpFe-(CO)P(C6H5)3] for effecting asymmetric reactions of an acyl group, including alkylation, aldol reactions, Michael additions. 

P-Vinylpyrrole complexes with pendant electron-withdrawing groups (56, 58, 60-62) are easily synthesized by the Michael addition of activated alkynes to r 2-pyrrole complexes as described earlier in this review (see Figure 13). 

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