Markedly chemoselective hydrogenation with retention of benzyl ester and N-Cbz functions using a heterogeneous Pd-fibroin catalyst
作者:Hironao Sajiki、Takashi Ikawa、Kosaku Hirota
DOI:10.1016/j.tetlet.2003.09.137
日期:2003.11
The chemoselective catalytic hydrogenation of acetylene, olefin and azido derivatives bearing benzyl ester and N-Cbz functionalities using a Pd-fibroin (Pd/Fib) catalyst was investigated. Perfect selectivity was accomplished, and the benzyl ester and N-Cbz functionalities are tolerated under the reaction conditions.
Palladium catalysts embedded on molecular sieves (MS3A and MS5A) were prepared by the adsorption of Pd(OAc)(2) onto molecular sieves with its in situ reduction to Pd-0 by MeOH as a reducing agent and solvent. 0.5% Pd/MS3A and 0.5% Pd/MS5A catalyzed the hydrogenation of alkynes, alkenes, and azides with a variety of coexisting reducible functionalities, such as nitro group, intact. It is noteworthy that terminal alkenes of styrene derivatives possessing electron-donating functionalities on the benzene nucleus were never hydrogenated under 0.5% Pd/MS5A-catalyzed conditions, while internal alkenes of 1-propenylbenzene derivatives were readily reduced to the corresponding alkanes. (C) 2012 Elsevier Ltd. All rights reserved.