Ionic hydrogenation of alkynes by HOTf and Cp(CO){sub 3}WH
- Brookhaven National Lab., Upton, NY (United States)
Alkynes can be hydrogenated at room temperature by an ionic hydrogenation method using triflic acid (CF{sub 3}SO{sub 3}H) as the proton donor and a transition metal hydride (Cp(CO){sub 3}WH) as the hydride donor. Reaction of PhC{triple_bond}CH with HOTf and Cp(CO){sub 3}WH gives ethylbenzene as the final product in high yield. Intermediates observed in this reaction are the vinyl triflate CH{sub 2}{double_bond}C(Ph)(OTf) and the geminal ditriflate Ph(CH{sub 3})C(OTf){sub 2}, which result from the addition of 1 or 2 equiv of HOTf to the C{triple_bond}C triple bond of the alkyne. Hydrogenation of PhC{triple_bond}CMe by HOTf and Cp(CO){sub 3}WH similarly observed in this reaction were the cis and trans isomers of the {beta}-methylstyrene complex [Cp(CO){sub 3}W-({eta}{sup 2}-PhHC{double_bond}CHCH{sub 3})]{sup +}[OTf]{sup -}. Hydrogenation of n-butyacetylene to n-hexane does occur upon reaction with HOTf/Cp(CO){sub 3}WH, but is very slow. In the absence of metal hydrides, 2-methyl-1-buten-3-yne reacts with HOTf to give the vinyl triflate CH{sub 2}{double_bond}CMeC(OTf){double_bond}CH{sub 2}, but reaction with HOTf and Cp(CO){sub 3}WH gives Me{sub 2}C{double_bond}C(OTf)Me. The key characteristics required for the metal hydride used in these hydrogenations are the ability to donate hydride in the presence for the metal hydride used in these hydrogenations are the ability to donate hydride in the presence of strong acid, and the absence of rapid decomposition of the hydride through reaction with the strong acid. Cp(CO){sub 3}WH meets these requirements, but HSiEt{sub 3}, while an effective hydride donor, is decomposed by HOTf on the time scale of these alkyne hydrogenation reactions.
- Research Organization:
- Brookhaven National Lab. (BNL), Upton, NY (United States)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 183496
- Journal Information:
- Journal of Organic Chemistry, Vol. 60, Issue 22; Other Information: PBD: 3 Nov 1995
- Country of Publication:
- United States
- Language:
- English
Similar Records
Insertion products from photolysis of Tp{prime}(CO){sub 3}WH and alkynes
Acyl, carbene, vinyl, and azavinylidene ligands in tungsten(II) hydridotris(3,5-dimethylpyrazolyl)borate alkyne complexes