title: Rhenium(VII) oxide catalyzed heteroacylative ring-opening dimerization of tetrahydrofuran.
abstract: Re(2)O(7), which is known primarily as a strong oxidant, was found to be a highly selective Lewis acid catalyst that affects the heteroacylative dimerization of THF at room temperature. This multicomponent reaction, which involves THF, trifluoroacetic anhydride (TFAA), and a carboxylic acid, produces a nonsymmetrical diester, RCO(2)(CH(2))(4)O(CH(2))(4)OCOCF(3), in high yields. The reaction is quite general with respect to the carboxylic acid but is highly selective for unsubstituted THF in preference to other cyclic ethers. It is also highly selective for TFAA in preference to other anhydrides. Isotope labeling experiments indicate that two of the five oxygen atoms in the product originate from THF; one comes from rhenium oxide, and the two carbonyl oxygens originate from the carboxylic acid and from TFAA. The catalytic cycle, which is proposed on the basis of these experiments, involves a multistep sequence of nucleophilic attacks, starting with an attack of a rhenium oxo ligand on a coordinated THF, then attack of the resultant alkoxide ligand on a second coordinated THF, nucleophilic addition of the resultant alkoxide ligand to the coordinated carboxylic acid (an intramolecular metal-oxygen bond metathesis), and, finally, electrophilic cleavage of the other coordinated alkoxide by TFAA to produce the nonsymmetrical diester. This synthetically useful reaction highlights the unique, frequently avoided Lewis acidity of transition-metal oxides.
authors.affiliation: Department of Molecular Biology and the Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
authors.forename: H Christine
authors.initials: HC
authors.lastname: Lo
authors.forename: Hongna
authors.initials: H
authors.lastname: Han
authors.forename: Lawrence J
authors.initials: LJ
authors.lastname: D'Souza
authors.forename: Subhash C
authors.initials: SC
authors.lastname: Sinha
authors.forename: Ehud
authors.initials: E
authors.lastname: Keinan
mesh_terms: D000089:Acetic Anhydrides; D000215:Acylation; D002264:Carboxylic Acids / Q000737:chemistry; D002384:Catalysis; D019281:Dimerization; D004952:Esters / Q000737:chemistry; D004988:Ethers, Cyclic / Q000737:chemistry; D005463:Fluoroacetates; D005663:Furans / Q000737:chemistry*; D008024:Ligands; D015394:Molecular Structure; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D012211:Rhenium / Q000737:chemistry*; D013696:Temperature; D014269:Trifluoroacetic Acid / Q000737:chemistry
chemical_list: D000089:Acetic Anhydrides; D002264:Carboxylic Acids; D004952:Esters; D004988:Ethers, Cyclic; D005463:Fluoroacetates; D005663:Furans; D008024:Ligands; D016877:Oxidants; C015428:perrhenate; C018674:tetrahydrofuran; C017958:trifluoroacetic anhydride; D012211:Rhenium; D014269:Trifluoroacetic Acid; D010100:Oxygen