| Abstract
| - Anthracene and related compounds function as lifetime-extending cofactors in the (meso-tetraphenylporphine)MnIIIchloride-catalyzed epoxidation of olefins. An experiment with a chiral porphyrin catalyst shows that enantioselectivityis preserved in the presence of the cofactor. Additional experiments show that (a) turnover number enhancementis greatest for the least reactive substrates, (b) derivatization of anthracene at the 9 and 10 positions largelyeliminates the enhancement effect, and (c) anthracene is ultimately converted to anthraquinone. The origin of theobserved enhancements is in the reaction of anthracene with the normally unreactive dimeric oxo-bridged form ofthe catalyst. This reaction, which produces anthraquinone, regenerates the catalytically active monomeric form ofthe manganese porphyrin.
- Anthracene unexpectedly elicits a substantial increase in turnover number for the catalytic epoxidation of styrene by a manganese oxo porphyrin. The origin of the increase is in repetitive regeneration of the active monomeric catalyst from the catalytically ineffective oxo-bridged dimer.
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