Ionic hydrogenation of alkynes by HOTf and Cp(CO){sub 3}WH

Journal Article · Fri Nov 03 04:00:00 EST 1995 · Journal of Organic Chemistry

DOI:https://doi.org/10.1021/jo00127a023· OSTI ID:183496

Luan, L; Song, J S; Bullock, R M ^[1]

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1. 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 Laboratory (BNL), Upton, NY
• DOE Contract Number: AC02-76CH00016
• OSTI ID: 183496
• Journal Information: Journal of Organic Chemistry, Journal Name: Journal of Organic Chemistry Journal Issue: 22 Vol. 60; ISSN 0022-3263; ISSN JOCEAH
• Country of Publication: United States
• Language: English

Related Subjects

40 CHEMISTRY
ALKYNES
CHEMICAL REACTION YIELD
HYDRIDES
HYDROGENATION
REACTION INTERMEDIATES
TUNGSTEN COMPLEXES