Properties and Reactivity of Conformationally Constrained Bicyclic Diarylprolinol Silyl Ethers as Organocatalysts

Bicyclic silyl ether derivatives 1, which are derived from simple chemical manipulations of trans-4-L-hydroxyproline, were recently proposed, by us, as conformationally constrained analogues of Jørgensen–Hayashi’s catalysts 2. Despite the structural similarities, 1 displays remarkable performance in iminium chemistry with respect to 2, but much lower reactivity in enamine chemistry. The peculiar structural features of 1 confer a pattern of reactivity between Jørgensen–Hayashi’s catalysts and MacMillan’s imidazolidinones.