title: Highly asymmetric intramolecular cyclopropanation of acceptor-substituted diazoacetates by Co(II)-based metalloradical catalysis: iterative approach for development of new-generation catalysts.
abstract: 3,5-Di(t)Bu-QingPhyrin, a new D(2)-symmetric chiral porphyrin derived from a chiral cyclopropanecarboxamide containing two contiguous stereocenters, has been developed using an iterative approach based on Co(II)-catalyzed asymmetric cyclopropanation of alkenes. The Co(II) complex of 3,5-Di(t)Bu-QingPhyrin, [Co(P2)], has proved to be a general and effective catalyst for asymmetric intramolecular cyclopropanation of various allylic diazoacetates (especially including those with α-acceptor substituents) in high yields with excellent stereoselectivities. The [Co(P2)]-based intramolecular metalloradical cyclopropanation provides convenient access to densely functionalized 3-oxabicyclo[3.1.0]hexan-2-one derivatives bearing three contiguous quaternary and tertiary chiral centers with high enantiomeric purity.
authors.affiliation: Department of Chemistry, University of South Florida, Tampa, Florida 33620-5250, United States.
authors.forename: Xue
authors.initials: X
authors.lastname: Xu
authors.forename: Hongjian
authors.initials: H
authors.lastname: Lu
authors.forename: Joshua V
authors.initials: JV
authors.lastname: Ruppel
authors.forename: Xin
authors.initials: X
authors.lastname: Cui
authors.forename: Silke
authors.initials: S
authors.lastname: Lopez de Mesa
authors.forename: Lukasz
authors.initials: L
authors.lastname: Wojtas
authors.forename: X Peter
authors.initials: XP
authors.lastname: Zhang