R,â-chiral aldehydes (Schemes 83 and 84), thus creating another stereocenter in the products.101 Since the Lewis acids used for generating the enolates have another open coordination site, these reactions should proceed via a Zimmermann-Traxler transition state. As discussed for the aldol reactions in chapter II.C.1, the geometry of the enolate explains the observed preference for the Felkin or the anti- Felkin product in addition to the bias of the â-stereocenter toward the 1,3-anti product.