D A. Evans Double Stereodifferentiating Bond Constructions-2 Chem 206 The Masamune-Heathcock generalizations hold to a point (2)-Titanium Enolates: The reference reactions (E)-Boron Enolates: The reference reactions TBSO SOo o TICl4. EtN-iPT2 B(c-hexh2 R-CHO OTBS O OH OTBS diastereoselection 94: 6 TBSo 0 OH Me Me ( c-hex)2BCL, Et3N MeMe Me M=B(9-BBN) syn: 10: 69 21% anti M=TICl4 syn: 21: 7. diastereoselection 96: 4 Me (E)-Boron Enolates: The matched cases ()-Titanium Enolates: The matched cases Me diastereoselection: anti: others O OTBS Me R=TBS: >99: 1(85% yield) R=PMB:>99:1(84%yed (E)-Boron Enolates: The mismatched cases (]-Titanium Enolates: The mismatched cases TBS R=TBS:52:48(83% diastereoselection 62: 38 (87%) CR=PMB: 81: 19(79% yield) Double Stereodifferentiating Aldol Reactions. The Documentation of" Partially B-center on RCHO can play a significant role in this marginal situation Matched" Aldol Bond Constructions". Evans, D A; Dart, M.J.; Duffy, J. L Rieger,D.L.JAcS1995,117,90739074.O Me Me Me B(c-hex)2 Me OTBS Me Me O OH Me Me Me Me Me Me OM Me O OH Me Me X OPMB Me Me OPMB X Me Me O OH Me Me Me TBSO Me O Me H O Me OTBS Me Me Me Me TBSO Me Me O Me Me OH Me O Me TBSO Me Me Me Me OR Me O H OR R OH Me Me O Me TBSO R Me O Me TBSO Me Me BR2 H O Me OR Me Me Me Me TBSO Me O Me Me OH OR Me Me BR2 O Me Me TBSO Me Me R TBSO Me O Me Me OH R OR Me Me OPMB Me O H TiCln O Me Me TBSO Me Me Me Me OTBS Me O H R TBSO Me O Me Me OH R OTBS TiCln O Me Me TBSO Me Me Me Me OTBS Me O H R TBSO Me O Me Me OH R OTBS R-CHO R-CHO OH Me Me O Me Me TBSO Me Me OTBS R OH Me Me O Me TBSO R OTBS R OH Me Me O Me TBSO R D. A. Evans Double Stereodifferentiating Bond Constructions-2 Chem 206 The Masamune-Heathcock generalizations hold to a point: (E)-Boron Enolates: The reference reactions diastereoselection 94 : 6 diastereoselection 96 : 4 (c-hex)2BCl, Et3N diastereoselection: anti : S others R = PMB: >99 : 1 (84% yield) R = TBS: >99 : 1 (85% yield) (E)-Boron Enolates: The matched cases R = TBS: 52 : 48 (83% yield) R = PMB: 81 : 19 (79% yield) (E)-Boron Enolates: The mismatched cases -center on RCHO can play a significant role in this marginal situation (Z)-Titanium Enolates: The reference reactions TiCl4 , EtN-iPr2 diastereoselection 96 : 4 + + 8% anti 21% anti syn: 21: 71 M = B(9-BBN) M = TiCl4 syn: 10: 69 (Z)-Titanium Enolates: The matched cases (Z)-Titanium Enolates: The mismatched cases diastereoselection 62 : 38 (87%) R = TBS: 87 : 13 (76%) "Double Stereodifferentiating Aldol Reactions. The Documentation of "Partially Matched" Aldol Bond Constructions". Evans, D. A.; Dart, M. J.; Duffy, J. L.; Rieger, D. L. JACS 1995, 117, 9073-9074