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. (C) 2009 Elsevier B.V. All rights reserved.