The chemoselectivehydrogenation of unsaturatedbonds and azide functionalities is achieved in the presence of nitrogroups by a heterogeneous palladiumcatalyst supported on molecular sieves (MS3A). The present method shows a wide-range of applicability with regard to substrates and the catalyst can be easily prepared and reused at least three times without any loss of activity.
A practical strategy has been developed for preparation of α-aryl ester derivatives by using a visible-light-induced Meerwein cascadereaction. This method uses molecular oxygen as an oxidant at room temperature without the need of hazardous reagents or harsh reaction conditions and provides a straightforward approach to pharmaceutically and synthetically useful α-aryl esters in moderate to good yields
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.