| SYNTHESIS |
Steric shielding alone can lead to enantioselective addition of singlet oxygen (1O2) to the double bond of enecarbamates to form dioxetanes with greater than 95% stereoselectivity. made this surprising finding in reactions of singlet oxygen with enecarbamates bearing oxazolidinone chiral auxiliaries. Even when steric shielding is due to just a single methyl group, the reaction proceeds with essentially complete stereochemical control. "Singlet oxygen has little if any steric demands," Steering it to one face of the reaction center through steric shielding "has not been believed possible for such a small molecule," he explains. The substrate they use adopts a conformation where one side of the double bond is completely shielded by a substituent of the chiral auxiliary. When the chiral auxiliary is detached from the dioxetane product, the dioxetane can be converted to highly optically pure chiral diols.
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