Details
| Originalsprache | Englisch |
|---|---|
| Seiten (von - bis) | 2125-2132 |
| Seitenumfang | 8 |
| Fachzeitschrift | Liebigs Annales |
| Ausgabenummer | 10 |
| Publikationsstatus | Veröffentlicht - Okt. 1997 |
| Extern publiziert | Ja |
Abstract
A study on the mechanism of the well-documented hypervalent iodine-mediated allylic oxidation of glycals leading to 2,3-dihydro-4H-pyran-4-ones is presented. Notable features are the isolation of ring-contracted by-products 6 and 7, which are produced upon oxidation of per-O-benzylated glycal 4, as well as the characterization of carbohydrate-derived tetrahydrofurfurals 12a and 13a, which are formed by the conformation-dependent oxidation of glycals 9a and 10b. In addition, the iodine(III)-mediated oxidation process has been studied by in situ NMR spectroscopy of fyxo-configured glycals 14a,b. Intermediate alkylphenyliodonium species 19b,d and 2-enopyranosides 16a and 20a have been characterized by their NMR signals. These data support a plausible mechanism that is initiated by electrophilic attack of the iodine (III) reagent on the electron-rich enol ether double bond of the glycal. This is followed by the breaking of a bond β,γ-positioned in relation to the carbohydrate-bound iodine and subsequent reductive elimination of iodobenzene. Thus, depending on the glycals employed, a number of diverse oxidation products may be formed.
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in: Liebigs Annales, Nr. 10, 10.1997, S. 2125-2132.
Publikation: Beitrag in Fachzeitschrift › Artikel › Forschung › Peer-Review
}
TY - JOUR
T1 - Product analysis in the iodine(III)-promoted oxidation of carbohydrate-derived cyclic enol ethers
T2 - A mechanistic study
AU - Harders, Jan
AU - Garming, Alfons
AU - Jung, Alexander
AU - Kaiser, Volker
AU - Monenschein, Holger
AU - Ries, Monika
AU - Rose, Lars
AU - Schöning, Kai Uwe
AU - Weber, Thomas
AU - Kirschning, Andreas
PY - 1997/10
Y1 - 1997/10
N2 - A study on the mechanism of the well-documented hypervalent iodine-mediated allylic oxidation of glycals leading to 2,3-dihydro-4H-pyran-4-ones is presented. Notable features are the isolation of ring-contracted by-products 6 and 7, which are produced upon oxidation of per-O-benzylated glycal 4, as well as the characterization of carbohydrate-derived tetrahydrofurfurals 12a and 13a, which are formed by the conformation-dependent oxidation of glycals 9a and 10b. In addition, the iodine(III)-mediated oxidation process has been studied by in situ NMR spectroscopy of fyxo-configured glycals 14a,b. Intermediate alkylphenyliodonium species 19b,d and 2-enopyranosides 16a and 20a have been characterized by their NMR signals. These data support a plausible mechanism that is initiated by electrophilic attack of the iodine (III) reagent on the electron-rich enol ether double bond of the glycal. This is followed by the breaking of a bond β,γ-positioned in relation to the carbohydrate-bound iodine and subsequent reductive elimination of iodobenzene. Thus, depending on the glycals employed, a number of diverse oxidation products may be formed.
AB - A study on the mechanism of the well-documented hypervalent iodine-mediated allylic oxidation of glycals leading to 2,3-dihydro-4H-pyran-4-ones is presented. Notable features are the isolation of ring-contracted by-products 6 and 7, which are produced upon oxidation of per-O-benzylated glycal 4, as well as the characterization of carbohydrate-derived tetrahydrofurfurals 12a and 13a, which are formed by the conformation-dependent oxidation of glycals 9a and 10b. In addition, the iodine(III)-mediated oxidation process has been studied by in situ NMR spectroscopy of fyxo-configured glycals 14a,b. Intermediate alkylphenyliodonium species 19b,d and 2-enopyranosides 16a and 20a have been characterized by their NMR signals. These data support a plausible mechanism that is initiated by electrophilic attack of the iodine (III) reagent on the electron-rich enol ether double bond of the glycal. This is followed by the breaking of a bond β,γ-positioned in relation to the carbohydrate-bound iodine and subsequent reductive elimination of iodobenzene. Thus, depending on the glycals employed, a number of diverse oxidation products may be formed.
KW - Carbohydrates
KW - Glycals
KW - Hypervalent iodine
KW - Mechanism
KW - Ring-contraction
KW - Tetrahydrofurans
UR - http://www.scopus.com/inward/record.url?scp=0009500001&partnerID=8YFLogxK
U2 - 10.1002/jlac.199719971015
DO - 10.1002/jlac.199719971015
M3 - Article
AN - SCOPUS:0009500001
SP - 2125
EP - 2132
JO - Liebigs Annales
JF - Liebigs Annales
SN - 0947-3440
IS - 10
ER -