Enantioselective epoxide polymerization using a bimetallic cobalt catalyst.
A highly active enantiopure bimetallic cobalt complex was explored for the enantioselective polymerization of a variety of monosubstituted epoxides. The polymerizations were optimized for high rates and stereoselectivity, with s-factors (k(fast)/k(slow)) for most epoxides exceeding 50 and some exceeding 300, well above the threshold for preparative utility of enantiopure epoxides and isotactic polyethers. Values for mm triads of the resulting polymers are typically greater than 95%, with some even surpassing 98%. In addition, the use of a racemic catalyst allowed the preparation of isotactic polyethers in quantitative yields. The thermal properties of these isotactic polyethers are presented, with many polymers exhibiting high T(m) values. This is the first report of the rapid synthesis of a broad range of highly isotactic polyethers via the enantioselective polymerization of racemic epoxides.
Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, United States.
Renee M
RM
Thomas
Peter C B
PC
Widger
Syud M
SM
Ahmed
Ryan C
RC
Jeske
Wataru
W
Hirahata
Emil B
EB
Lobkovsky
Geoffrey W
GW
Coates
D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry*; D015394:Molecular Structure; D058105:Polymerization; D011126:Polypropylenes / Q000737:chemistry; D013237:Stereoisomerism
D004852:Epoxy Compounds; D011126:Polypropylenes; D003035:Cobalt