Aluminium(III) trifluoromethanesulfonate as an efficient catalyst for the intramolecular hydroalkoxylation of unactivated olefins: experimental and theoretical approaches.
The Al(OTf)(3)-catalyzed cycloisomerization of unactivated unsaturated alcohols was studied from experimental and theoretical points of view. A series of cyclic ethers was obtained in excellent yields and regioselectivities. This catalyst system provides one of the most straightforward routes to cyclic ethers with Markovnikov-type regioselectivity under mild conditions. Theoretical and NMR studies were carried out in order to better determine the mechanism of this reaction. The NMR studies were in agreement with preferential complexation of Al(OTf)(3) to the oxygen atom of the unsaturated alcohol, but did not exclude complexation to the double bond of the alcohol. Theoretical calculations indicated strong acidification of the hydroxyl proton when Al(OTf)(3) was complexed to the alcohol oxygen atom. A plausible catalytic cycle for the Al(OTf)(3)-catalyzed intramolecular hydroalkoxylation of unactivated olefins is proposed.
Coulombel
Lydie
L
Laboratoire de Chimie des Molécules Bioactives et des Arômes, UMR-CNRS 6001, Université de Nice-Sophia Antipolis, Parc Valrose, 06108 Nice Cedex 2, France.
Rajzmann
Michel
M
Pons
Jean-Marc
JM
Olivero
Sandra
S
Duñach
Elisabet
E
D000438:Alcohols / Q000737:chemistry*; D000475:Alkenes / Q000737:chemistry*; D000535:Aluminum / Q000737:chemistry*; D002384:Catalysis; D004988:Ethers, Cyclic / Q000138:chemical synthesis*; D006900:Hydroxylation; D008698:Mesylates / Q000737:chemistry*
D000438:Alcohols; D000475:Alkenes; D004988:Ethers, Cyclic; D008698:Mesylates; D000535:Aluminum; C012077:trifluoromethanesulfonic acid