- Intramolecular Cyclization of Some Unsaturated Alcohols by Means of Thallium Triacetate
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Reactions of some primary and secondary Δ4-, Δ5- and Δ6-alkenols with thallium triacetate (TTA) in benzene, acetic acid and chloroform as solvent have been investigated.When terminally unsubstituted Δ4-alkenols, such as 4-penten-1-ol (5a) and 5-hexen-2-ol (5b), are treated with TTA in benzene, β-acetoxylated tetrahydrofurans 8a and 8b are obtained.However, when the reaction is carried in acetic acid the products are both regioisomers, i.e. five- and six-membered cyclic ethers (8a, 8b, 7a and 7b). 4-Methyl-4-penten-1-ol (5c) is converted in benzene into a mixture of products (8c and 7c) in which the tetrahydropyran derivative 7c is predominant, and in acetic acid it is the sole cyclization product.Terminally dialkylated alkenols, such as 5-methyl-4-hexen-1-ol (1b) and 6-methyl-5-hepten-2-ol (1c), are converted into β-acetoxylated (4b and 4c) and unsaturated cyclic ethers (9a and 9b), in both cases of the tetrahydrofuran type. 5-Hexen-1-ol (10) and 6-hepten-1-ol (11) cyclize to the corresponding six- (13) and seven-membered cyclic ether (14), respectively.Organothallium intermediates have been isolated and identified in the cases of alcohols 5a, 5c and 10, proving that the TTA addition to the double bond has originally obeyed the Markovnikov rule. Key Words: Alcohols, unsaturated / Thallium triacetate
- Mihailovic, Mihailo Lj.,Vuki, Rastko,Konstantinovic, Stanimir,Milosavljevic, Slobodan,Schroth, Gerhard
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p. 305 - 310
(2007/10/02)
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- A Stereochemical Test for Ether-Oxygen Participation and Oxonium Ion Formation in thr Acetolysis of 3-Tetrahydropyranyl Brosylate
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Optically active tetrahydropyran-3-ol was obtained by the horse liver alcohol dehydrogenase (HLADH)-catalysed reduction of tetrahydropyran-3-one, and the corresponding brosylate was prepared.Acetolysis of the optically active brosylate gave racemic 3-tetrahydropyranyl acetate as well as varying amounts of racemic tetrahydropyran-3-ol.Within experimental error, the polarimetric rate of acetolysis was the same as the previously measured tetrimetric rate.The results provide no support for the intermediacy of a bicyclic oxonium ion in the acetolysis of 3-tetrahydropyranyl brosylate.
- Dunkin, Ian R.,Paul, Alan J.,Suckling, Colin J.,Valente, Edward,Wood, Hamish C. S.
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p. 1323 - 1326
(2007/10/02)
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