Organocatalysis aldol reaction

The formation of covalent substrate-catalyst adducts might occur, e.g., by single-step Lewis-acid-Lewis-base interaction or by multi-step reactions such as the formation of enamines from aldehydes and secondary amines. The catalysis of aldol reactions by formation of the donor enamine is a striking example of common mechanisms in enzymatic catalysis and organocatalysis - in class-I aldolases lysine provides the catalytically active amine group whereas typical organocatalysts for this purpose are secondary amines, the most simple being proline (Scheme 2.2). 

Guillena G, Najera C et al (2007) Enantioselective direct aldol reaction the blossoming of modem organocatalysis. Tetrahedron Asymmetry 18 2249-2293... 

Cobb, A.J.A., Shaw, D.M., Longbottom, D.A., Gold, J.B. and Ley, S.V. (2005) Organocatalysis with proline derivatives improved catalysts for the asymmetric Mannich, nitro-Michael and aldol reactions. Org. Biomol. Chem., 3, 84. 

Other reviews deal with aldol additions of group 1 and 2 enolates,103 direct catalytic asymmetric aldol reactions catalysed by chiral metal complexes,104 the exploitation of multi-point recognition in catalytic asymmetric aldols,105 and recent progress in asymmetric organocatalysis of aldol, Mannich, Michael, and other reactions.106... 

Michael-aldol reaction as an alternative to the Morita-Baylis-Hillman reaction 14 recent results in conjugate addition of nitroalkanes to electron-poor alkenes 15 asymmetric cyclopropanation of chiral (l-phosphoryl)vinyl sulfoxides 16 synthetic methodology using tertiary phosphines as nucleophilic catalysts in combination with allenoates or 2-alkynoates 17 recent advances in the transition metal-catalysed asymmetric hydrosilylation of ketones, imines, and electrophilic C=C bonds 18 Michael additions catalysed by transition metals and lanthanide species 19 recent progress in asymmetric organocatalysis, including the aldol reaction, Mannich reaction, Michael addition, cycloadditions, allylation, epoxidation, and phase-transfer catalysis 20 and nucleophilic phosphine organocatalysis.21... 

ASYMMETRIC ORGANOCATALYSIS OF ALDOL REACTIONS 409 TABLE 6.11 Effect of Catalyst on the Direct Asymmetric Aldol Reaction"... 

Organocatalysis Carbon-carbon bond formation Aldol reaction... 

This class of catalysts covers chemocatalysts that do not contain a transition metal. The class has been known for many years, but it is relatively recently that the term organocatalyst has been used (209). A wide variety of transformations can be performed, which is currently an area of intense research (209-218). Table 5 (220-252) summarizes some key transformations in which organocatalysis can be useful. Reactions range from the asymmetric epoxidation of alkenes, which need not be conjugated to another functional group, to aldol reactions and... 

Table 1.1 Aldol reaction organocatalysis working under biphasic aqueous... 

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