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Org. Biomol. Chem., 2006, 4, 2019 - 2024, DOI: 10.1039/b602618d
Enhanced stereocontrol in Diels–Alder reactions of chiral dienols
Tory N. Cayzer, Natalie A. Miller, Michael N. Paddon-Row and Michael S. Sherburn
This combined experimental–computational investigation demonstrates that the presence of a removable bromine substituent on a diene leads to complete
-diastereofacial and endo/exo stereoselection in both intermolecular and intramolecular Diels–Alder reactions. The influence of the bromine upon stereoselectivity is dramatic: the cycloaddition of nonbrominated precursor 18E, for example, gives four diastereomeric products in a 55
131616 ratio; the bromine-containing analogue gives one stereoisomer within the limits of detection. The examination of B3LYP/6-31+G(d) transition structures allows an interpretation of these experimental findings. A method for the completely stereoselective synthesis of complimentary diastereomeric products ( 30Z and 31Z) from the same simple starting materials ( 28 and 2) is reported. Discrepancies between calculation and experiment in an earlier investigation into the Diels–Alder reaction are explained.
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