Hypervalent Iodine Oxidants: Structure and Kinetics of the Reactive Intermediates in the Oxidation of Alcohols and 1,2-Diols by o-Iodoxybenzoic Acid (IBX) and Dess−Martin Periodinane. A Comparative 1H-NMR Study
Alcohols and 1,2-diols oxidation by o-iodoxybenzoic acid (IBX) has been examined by 1H-NMR spectroscopy. Reversible formation of reactive intermediates, iodic esters 5, has been observed, and their structures in DMSO-d 6 solution have been defined as 10-I-4 axial alkoxyiodinane oxides by comparison...
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Published in | Journal of organic chemistry Vol. 61; no. 26; pp. 9272 - 9279 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
27.12.1996
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Online Access | Get full text |
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Summary: | Alcohols and 1,2-diols oxidation by o-iodoxybenzoic acid (IBX) has been examined by 1H-NMR spectroscopy. Reversible formation of reactive intermediates, iodic esters 5, has been observed, and their structures in DMSO-d 6 solution have been defined as 10-I-4 axial alkoxyiodinane oxides by comparison of the chemical shift difference data with those obtained for Dess−Martin periodinane (DMP)−alcoholate and −diolate adducts. The dichotomous behavior exhibited by IBX and DMP with 1,2-diols can be explained in terms of the different architecture of the reactive intermediates involved in the oxidation. With aliphatic alcohols, kinetic evidences support a two-step reaction mechanism involving a fast pre-equilibrium step leading to 5, followed by a rate-determining disproportionation step. With electronically activated benzyl alcohol, the attainment of pre-equilibrium is largely dependent on initial water concentration as a consequence of a particularly high k 2 value. The influence of the alcohol structure on measured equilibrium (K eq) and rate constants (k 2) and the effect of water on the overall reaction rate are discussed. |
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Bibliography: | istex:E6967645AF657D28020C5C8B01A8B791B9AD1835 ark:/67375/TPS-QFNDSHX5-5 Abstract published in Advance ACS Abstracts, December 1, 1996. |
ISSN: | 0022-3263 1520-6904 |
DOI: | 10.1021/jo961044m |