Cascade Processes Initiated by Conjugate Addition via Enamine Activation

2 Cascade Processes Initiated by Conjugate Addition via Enamine Activation 

After the Michael reaction step had taken place, an intermediate containing both an iminiiim and an enamine moiety was generated and their direct reaction between each other followed by elimination was proposed to account for 

E-ajp-unsaturated ester was employed, while a single diastereoisomer was obtained using the corresponding Z substrate. This reaction design has also been extended to the use of an a,p-unsaturated aldehyde as the initial Michael acceptor, in this case it being necessary to consider the possible dual activation of the Michael donor and acceptor by the catalyst through the formation of the corresponding enamine and iminium intermediates.  

However, it is in this context where the use of primary amines as catalysts demonstrates the high performance of this concept. As has already been mentioned in Chapter 2, primary amines are much more efficient catalysts for the activation of ketones than the corresponding secondary amines due to the formation of a less sterically congested enamine or iminium ion and also because of the more efficient geometry control in their formation. For example, primary amine 28a was found to be able to activate a-enolizable enones toward 

3 Michael/Michael/Aldol Triple Cascade Reactions 

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