Yoshinaga Y, Yamamoto T, Suginome M. Chirality-Switchable 2,2'-Bipyridine Ligands Attached to Helical Poly(quinoxaline-2,3-diyl)s for Copper-Catalyzed Asymmetric Cyclopropanation of Alkenes.
ACS Macro Lett 2017;
6:705-710. [PMID:
35650874 DOI:
10.1021/acsmacrolett.7b00352]
[Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Helical poly(quinoxaline-2,3-diyl)s copolymers PQXbpy consisting of a coordinating unit, which bears a varied achiral, substituted 2,2'-bipyridyl pendant, and a chiral unit bearing chiral side chains were synthesized and used as a ligand in copper-catalyzed asymmetric cyclopropanation of olefins with diazoacetates, giving up to 91:9 er with high chemical yield. The enantioselection relied on the helical structure of PQXbpy. A single PQXbpy afforded either of a pair of enantiomers with high enantioselectivity by switching its helical sense by changing the reaction solvent from pure toluene to a 3/1 mixture of toluene and 1,1,2-trichloroethane.
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