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Origins of Stereoselectivity of Chiral Vicinal Diamine-Catalyzed Aldol Reactions

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journal contribution
posted on 14.11.2016, 00:00 by Adam Simon, Alexander J. Yeh, Yu-hong Lam, K. N. Houk
The sources of asymmetric induction in aldol reactions catalyzed by cinchona alkaloid-derived amines, and chiral vicinal diamines in general, have been determined by density functional theory calculations. Four vicinal diamine-catalyzed aldol reactions were examined. The cyclic transition states of these reactions involve nine-membered hydrogen-bonded rings in distinct conformations. Using nomenclature from eight-membered cycloalkanes, the heavy atoms of the low-energy transition states are in crown (chair–chair) and chair-boat conformations. The factors that control which of these are favored have been identified.