Combination with Organocatalysis

In a complex system like this, several control experiments are necessary. A characteristic set is listed in Table 12.12. Without any of the catalysts (entry 1), or with only one of the catalysts (entries 2 and 3), no product is formed. Only the combination of the gold and the organocatalyst affords the desired product (entry 4). 

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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... 

Besides the utilization of chiral secondary amines to achieve a LUMO-lowering activation as well as face discrimination, the use of achiral secondary amines in combination with a chiral counterion also proved to be highly promising for such transformations. This strategy resembles the use of achiral metal catalysts in combination with a chiral ligand to achieve a stereoselective transformation (206-208). It is due to Benjamin List that the elegant concept of asymmetric counteranion-directed catalysis (ACDC) has found widespread applications in organocatalysis at the present time (209-212). 

It has been shown in this chapter that combined iminium-enamine catalyzed approaches offer the potential to achieve complex (multistep) transformations in a single operational step, thus giving access to high structural complexity combined with excellent effectivity. In addition, it was pointed out also that organocatalysis can be used successfully when combined with metal catalysis e.g. metathesis). Although these complex approaches have been pursued only for the last few years, the results obtained so far are very promising and thus this methodology should be applied more widely in the future (Table 3). 

Given the huge diversity and rapid growth in organocatalysis, can this area continually progress The power of many organocatalytic transformations lies in their simple experimental protocols and catalyst designs combined with the... 

Organocatalysis in combination with oxidants enables intramolecular asymmetric a-arylation of carbonyl compounds. In 2009, Nicolaou and MacMillan independently reported asymmetric a-arylation of aldehydes (Scheme 7.15). Using MacMillan s imidazoline catalyst and an appropriate... 

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