The Formation of Cyclic Ethers by Intramolecular Addition and Substitution Processes in the Reaction of Olefinic Alcohols with Lead Tetraacetate. Part I. Preliminary communication
✍ Scribed by Mihailo Lj. Mihailović; Živorad Čeković; Jezdimir Stanković; Nebojša Pavlović; Stanimir Konstantinović; Silvija Djokić-Mazinjanin
- Publisher
- John Wiley and Sons
- Year
- 1973
- Tongue
- German
- Weight
- 261 KB
- Volume
- 56
- Category
- Article
- ISSN
- 0018-019X
No coin nor oath required. For personal study only.
✦ Synopsis
The lead tetraacetate (LTA) oxidation of saturated alcohols in non-polar solvents affords usually as major products unsubstituted tetrahydrofuran-type ethers, the formation of which involves intramolecular 1,5-hydrogen abstraction by the initially produced alkoxy radicals, followed by internal attack of the hydroxylic oxygen on the electron-deficient &carbon atom [Z]. On the other hand, when treated with LTA in benzene, unsaturated alcohols containing a spatially accessible A4or A5-olefinic linkage undergo intramolecular addition of the hydroxylic oxygen to the double bond, resulting in the formation of acetoxylated or unsaturated five-membered cyclic ethers (from A4-alkenols) and six-membered cyclic ethers (from A4and d5-alkenols)
The mechanistic course of this internal cyclization is not as yet quite clear; several possibilities have been envisaged, such as initial attack of LTA on the hydroxyl group or on the ethylenic grouping, followed by a free-radical or ionic reaction sequence, or a successive combination of homolytic and heterolytic steps [2-41 3).
In this paper we present results of the LTA oxidation of some simple, conformationally mobile unsaturated open-chain alcohols containing an unsubstituted terminal A3-, A4-, A5-, d6-andA7-double bond. Products and yields of these reactions are summarized in the Scheme *).
The following comments about the results obtained can be made.
- The absence of cyclic ethers among the reaction products indicates that in A3alkenols, such as 1-octen-4-01 ( l ) , the hydroxyl oxygen does not undergo intramolecular addition to the double bond or intramolecular substitution at the saturated &carbon 1) z j
3)
Commun. 29 on 'Reactions with lead tetraacctate'. For paper 28 see [l].