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Mechanistic studies of alkene epoxidation catalyzed by nickel(II) cyclam complexes. /sup 18/O labeling and substituent effects

Journal Article · · J. Am. Chem. Soc.; (United States)
DOI:https://doi.org/10.1021/ja00226a029· OSTI ID:6048347
; ;

The oxidations of cyclohexene and various aryl-substituted alkenes are catalyzed by the cyclam (1,4,8,11-tetraazacyclotetradecane) complex of Ni(NO/sub 3/)/sub 2/ with iodosylbenzene as terminal oxidant. Epoxides are the major products; however, small amounts of ring-opened products, over-oxidation to ketones or aldehydes, and allylic oxidation of cyclohexene are also observed. E olefins are more reactive than the corresponding Z olefins in contrast to the results of iron porphyrin catalysis, and kinetic studies of para-substituted styrenes indicate that the reaction is facilitated by electron-donating substituents. Labeling studies with PhI/sup 18/O confirm that the epoxide oxygen is derived from PhIO while allylic oxidation and over-oxidation products involve both PhIO and exogenous sources of oxygen. A pericyclic mechanism for the formation of PhCHO is proposed along with the intermediacy of a high-valent nickel-oxo complex as the active oxidant. These results are discussed in light related transition-metal/PhIO oxidation mechanisms.

Research Organization:
State Univ. of New York, Stony Brook (USA)
OSTI ID:
6048347
Journal Information:
J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 110:18; ISSN JACSA
Country of Publication:
United States
Language:
English

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKENES
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
COMPLEXES
DATA
EPOXIDES
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
HYDROCARBONS
INFORMATION
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LABELLED COMPOUNDS
LABELLING
LIGHT NUCLEI
NICKEL COMPLEXES
NUCLEI
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDATION
OXYGEN 18
OXYGEN ISOTOPES
REACTION KINETICS
STABLE ISOTOPES
SYNTHESIS
TRANSITION ELEMENT COMPLEXES
YIELDS