D A. Evans Enantioselective C=O Addition: Noyori Catalyst-2 Chem 115 Other Catalysts for the R2Zn Addition Process Explanation for Nonlinearity of DAlB Catalyst Me3C Et 97%ee.(S) 100%ee.(R) 95%ee.(S) (S, S)dimer (R, R)dimer 90%ee.(R) 90%ee(R) 90%ee.(R) (Results are cited for the reaction of benzaldehyde and Et2Zn) Problem: Rationalize the stereochemical course of each of the catalysts (S)catalyst (R)catalyst Non-linear effects observed with the Noyori Catalyst(DAlB-Zn) There is no corel ion hetween I (S, R)dimer Et2Zn PhCHO (%ee) bservations (S,S)dimer dissociates upon addition of RCHo effects catalys 25%ee Catalyst affords product in 95%ee (s, R )dimer is overwhelmingly more stable than(s,S)homodimer a(S, R )dimer is ineffective as a catalyst %ee of catalyst 19A02Et2Zn11/1900149PMOther Catalysts for the R2Zn Addition Process D. A. Evans Enantioselective C=O Addition: Noyori Catalyst-2 Chem 115 ■ Non-linear effects observed with the Noyori Catalyst (DAIB-Zn) Product (%ee) 100 %ee of catalyst 100 25% ee Catalyst affords product in 95% ee. There is no correlation between catalyst and product ee. Et2Zn + PhCHO (S,S) dimer (R,R) dimer + (S) catalyst (R) catalyst (S) catalyst 90% e.e. (R) 90% e.e. (R) 90% e.e. (R) (Results are cited for the reaction of benzaldehyde and Et2Zn) 97% e.e. (S) 100% e.e. (R) 95% e.e. (S) Problem: Rationalize the stereochemical course of each of the catalysts Explanation for Nonlinearity of DAIB Catalyst (S,R) dimer Observations ■ (S,S) dimer dissociates upon addition of RCHO & effects catalysis ■ (S,R) dimer is overwhelmingly more stable than (S,S) homodimer ■ (S,R) dimer is ineffective as a catalyst Ph Me OH O Zn Me2 N Me Zn Me Me2 N O Zn Me Me2 N O O Zn N Me2 Me Zn O O Zn Me NMe2 Me2 N Me Zn O O Zn Me NMe2 N Zn O Me Ph Ph Et Zn Et Ph H N O Me3C Me2 N Me Li O N Me Me N Me H H Ph H Ph N O N Li N Me Me Me Me N Zn N Bu Me O Et Li Li Bu Ph 19A-02-Et2Zn-1 1/19/00 1:49 PM