Pd(0)–polyethyleneimine complex as a partial hydrogenation catalyst of alkynes to alkenes

We have developed a Pd(0)–polyethyleneimine [Pd(0)–PEI] complex for the selective partial hydrogenation of alkynes to the corresponding alkenes. Notably, Pd(0)–PEI catalyzed the partial hydrogenation of mono-substituted alkynes with an excellent selectivity (77–100%), which was very difficult to achieve even with the Lindlar catalyst. Moreover, the use of Pd(0)–PEI led to no reduction in the other reducible functionalities, such as the N-benzyloxycarbonyl (N-Cbz), benzyl ester, benzyl ether and O-tert-butyldimethylsilyl (O-TBS) protective groups; that is, Pd(0)–PEI offers a concise synthetic route to a variety of functionalized alkenes.

A Pd(0)–polyethyleneimine (PEI) complex was prepared by mixing Pd(OAc)2 and PEI under H2 atmosphere, and used as a catalyst for the partial hydrogenation of a variety of mono- and di-substituted alkynes producing the corresponding (cis-)alkenes with high selectivity. Moreover, the Pd(0)–PEI complex catalyzed the chemoselective hydrogenation of only mono-substituted alkynes with other reducible functionalities untouched.Figure optionsDownload as PowerPoint slide