Controlled hydrogenation of diphenylacetylene using alkylammonium formate

A simple and straightforward semihydrogenation of alkyne to alkene with triethanolamine and formic acid in the presence of PdCl₂ has been described. Although hydrogenation using formic acid as a hydrogenation source has been used in combination with amines previously, few reports are available concerning the associated reactivity. We demonstrated that reactivity changes depending on the type of amine used in the hydrogenation. Further, this reaction requires no strict time control, making it a useful tool in organic synthesis.