Additions to silyl ketene acetals

A pyridine derivative bearing an electron withdrawing group in the position p to the nitrogen can undergo addition with silyl ketene acetals in the presence of some ion-exchanged montmorillonite clays (e.g. equation 4.36) [148]. The nature of the cation present is vital to the activity of the catalyst. 

The same catalysts promote the addition of silyl ketene acetals to a,p-acetylenic esters. Substituted a,p-acetylenic esters mainly undergo 1,2-addition (e.g. equation 4.37) whilst unsubstituted ones favour 1,4-addition (e.g. equation 4.38) [149]. 

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Type I Asymmetric Acyl Addition to 7r-Nucleophiles Steglich and Related Rearrangements and Additions to Silyl Ketene Acetals/lmines... 

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