Terminal and internal olefin epoxidation with cobalt(II) as the catalyst: evidence for an active oxidant Co(II)-acylperoxo species.
A simple catalytic system that uses commercially available cobalt(II) perchlorate as the catalyst and 3-chloroperoxybenzoic acid as the oxidant was found to be very effective in the epoxidation of a variety of olefins with high product selectivity under mild experimental conditions. More challenging targets such as terminal aliphatic olefins were also efficiently and selectively oxidized to the corresponding epoxides. This catalytic system features a nearly nonradical-type and highly stereospecific epoxidation of aliphatic olefin, fast conversion, and high yields. Olefin epoxidation by this catalytic system is proposed to involve a new reactive Co(II)-OOC(O)R species, based on evidence from H(2)(18)O-exchange experiments, the use of peroxyphenylacetic acid as a mechanistic probe, reactivity and Hammett studies, EPR, and ESI-mass spectrometric investigation. However, the O-O bond of a Co(II)-acylperoxo intermediate (Co(II)-OOC(O)R) was found to be cleaved both heterolytically and homolytically if there is no substrate.
Department of Fine Chemistry, Seoul National University of Science & Technology, Seoul 139-743, Korea.
Min Young
MY
Hyun
Soo Hyun
SH
Kim
Young Joo
YJ
Song
Hong Gyu
HG
Lee
Young Dan
YD
Jo
Jin Hoon
JH
Kim
In Hong
IH
Hwang
Jin Young
JY
Noh
Juhye
J
Kang
Cheal
C
Kim
D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D003035:Cobalt / Q000737:chemistry*; D004852:Epoxy Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010084:Oxidation-Reduction
D000475:Alkenes; D004852:Epoxy Compounds; D009942:Organometallic Compounds; D003035:Cobalt