P conjugate addition reactions

Perlmutter P. Conjugate Addition Reactions in Organic Synthesis, Baldwin J. E. and Magnus P. D. (eds), Pergamon Press, Oxford, 1992. 

Perlmutter, P. Conjugate Addition Reactions in Organic Synthesis, Pergamon Oxford, 1992. 

The mechanism of the Fiesselmann reaction between methylthioglycolate and a,P-acetylenic esters proceeds via consecutive base-catalyzed 1,4-conjugate addition reactions to form thioacetal Enolate formation, as a result of treatment with a stronger base, causes a Dieckmann condensation to occur providing ketone 8. Elimination of methylthioglycolate and tautomerization driven by aromaticity provides the 3-hydroxy thiophene dicarboxylate 9. 

In a, P-unsaturated carbonyl compounds and related electron-deficient alkenes and alkynes, there exist two electrophilic sites and both are prone to be attacked by nucleophiles. However, the conjugated site is considerably softer compared with the unconjugated site, based on the Frontier Molecular Orbital analysis.27 Consequently, softer nucleophiles predominantly react with a, (i-unsaturated carbonyl compounds through conjugate addition (or Michael addition). Water is a hard solvent. This property of water has two significant implications for conjugate addition reactions (1) Such reactions can tolerate water since the nucleophiles and the electrophiles are softer whereas water is hard and (2) water will not compete with nucleophiles significantly in such... 

This manganese-copper-catalyzed conjugate addition reaction compares favorably with the classical copper-catalyzed reaction. The two reactions are easily and similarly carried out under mild conditions, but the first one gives higher yields. This difference, already observed in the case of p-monosubstituted o,p-ethylenic ketones, is especially noticeable with p,p-disubstituted or [Pg.70]

P. Perlmutter, Conjugate Addition Reactions in Organic Synthesis, Pergamon Press, Oxford, 1992. a) M. Shibasaki, H. Sasai, T. Arai, Angew. Chem. 1997, 309, 1290 Angeiv. Chem. Int. Ed. 1997, 36, 1236 b) J. Leonard, Contemp. Org. Synth. 1994, 3, 387. 

Other types of conjugate additions with chiral thioureas were also explored by Connon. P-Substituted nitro-olefms were used in the conjugate addition reaction with dimethyl chloromalonate 115 to generate chiral, functionalized nitrocyclopro-panes [73]. Utility of the nitrocyclopropanes was demonstrated in the one-step modification towards other functionalized chiral building blocks (Scheme 24). 

Formation of C-C bonds remains the ultimate challenge to the synthetic chemist. The employment of new synthetic methods in complex target synthesis can be frustrated by a lack of functional group tolerance and substrate specificity. These problems can be somewhat alleviated within conjugate addition reactions by the use of secondary amine catalysts where a number of important and highly selective methods have been developed. Two principle classes of nucleophile have been shown to be effective in the iminium ion activated conjugate addition of carbon nucleophiles to a,P-unsaturated carbonyl systems aryl, heteroaromatic and vinyl... 

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