物理有机化学PPT-复旦大学-王全瑞 3.Conformational Analysis-3.2.pptxVIP

See last Lecture for previous discussionAddition from indicated olefin face avoids eclipsing A B Hs(better hyperconjugative stabilization of transition state)How do we account for the high selectilvities in the oxidation of the indicated olefin?Martinelli has carried out further studies on related structures...........Enantioselectivities are the same, regardless of whether or not the starting material is chiral, even at low temperatures. Further, reaction in the absence of (-)-sparteine results in racemic product.Note that the two alkyllithium complexes MUST be in equilibrium, as the enantioselectivity is the same over the course of the reaction. If they were not equilibrating, the enantioselectivity should be higher at lower conversions.This is a case of Dynamic Kinetic Resolution: Two enantiomeric alkyllithium complexes are equilibrating during the course of a reaction with anElectrophile.