Manganese catalysts with molecular recognition functionality for selective alkene epoxidation.
Selective epoxidation of alkenes is possible with a new manganese porphyrin catalyst, C(PMR), that uses hydrogen bonding between the carboxylic acid on the substrate molecule and a Kemp's triacid unit. For two out of three olefin substrates employed, molecular recognition prevents the unselective oxidation of C-H bonds, and directs oxidation to the olefin moiety, giving only epoxide products. Weak diastereoselectivity is observed in the epoxide products, suggesting that molecular recognition affects the orientation of the catalyst-bound substrate. The previously reported manganese terpyridine complex C(TMR) is shown to be a superior epoxidation catalyst to the porphyrin catalyst C(PMR). Good conversion of 2-cyclopentene acetic acid (substrate S2) with C(PMR) is consistent with molecular modeling, which indicates a particularly good substrate/catalyst match. Evidence suggests that hydrogen bonding between the substrate and the catalyst is critical in this system.
Hull
Jonathan F
JF
Chemistry Department, Yale University, 225 Prospect Street, New Haven, Connecticut 06511, USA.
Sauer
Effiette L O
EL
Incarvito
Christopher D
CD
Faller
J W
JW
Brudvig
Gary W
GW
Crabtree
Robert H
RH
D000085:Acetates / Q000737:chemistry; D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D004852:Epoxy Compounds / Q000737:chemistry*; D007052:Ibuprofen / Q000737:chemistry; D008345:Manganese / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity
D000085:Acetates; D000475:Alkenes; D004852:Epoxy Compounds; D008345:Manganese; D007052:Ibuprofen