Preparation and catalytic evaluation of a palladium catalyst deposited over two-dimensional zeolite ITQ-2 modified with N-donor groups
Abstrakt
Two-dimensional zeolite ITQ-2 was reacted successively with (3-chloropropyl)triethoxysilane, 2-(N,N-diethylamino)ethylamine, and ammonia to give a support bearing the Si(CH2)3NHCH2CH2NEt2 groups at the surface. Subsequent treatment with palladium(II) acetate afforded an immobilized palladium catalyst 3, which was tested in the Heck coupling of n-butyl acrylate with bromobenzene to give n-butyl cinnamate (4).
This (pre)catalyst, which acts as a source of active metal species for the reaction occurring in the liquid phase, showed good activity in N,N-dimethylformamide and N,N-dimethylacetamide at 150 degC. Reaction tests with different bases revealed a pronounced effect of the base additive on the course of the catalyzed process in terms of both the activity (yield of the coupling product) and selectivity [amount of n-butyl 3, 3-diphenylacrylate (5) resulting from twofold arylation].
Among the hydrated bases, the best yields of 4 were obtained in reactions performed in the presence of CH3CO2Na.3H2O and Na3PO4.12H2O, while that with Na2CO3.10H2O furnished considerably worse results. The use of the respective anhydrous bases not only decreased the yield of 4 but also incited the formation of the unwanted doubly arylated product 5.