Silyl-protected diarylprolinol catalysts

The carbanion -type reactivity of dienamine activation can be promoted by a silyl-protected diarylprolinol catalyst in the presence of reactive electrophilic species, such as nitroolefins or diarylmethanols (Scheme 2.10) [20]. Although both direct addition (a-addition) and vinylogous addition (y-addition) are viable reaction pathways, the a-reactivity is the more typical one and usually provides better selectivities due to more effective shielding of the a-position by the aminocatalyst. Interestingly, the a-/y-selectivity of dienamine-mediated carbanion -type addition reactions seems to be strongly influenced by the substitution pattern of the enal reactant For example, it was demonstrated that y,y-disubstituted enals favor the a-addition product while y-functionaUzation is the predominant reaction pathway for y-monosubstituted enals. 

For selected examples of carbanion -type dienamine activation promoted by silyl-protected diarylprolinol catalysts, see ... 

For selected examples of diene -type dienamine activation promoted by silyl-protected diarylprolinol catalysts, see (a) Bertelsen, S., Marigo, M., Brandes, S., Diner, P., and Jorgensen, K.A. (2005)... 

In 2005 j0rgensen [12] and Hayashi [13] developed almost at the same time diarylprolinol derivatives protected as silyl ethers (Figure 33.4) as a suitable catalysts for rmtne and enamtne activation. 

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