RESUMO
In Nature, incompatible catalytic transformations are being carried out simultaneously through compartmentalization that allows for the combination of incompatible catalysts in tandem reactions. Herein, we take the compartmentalization concept to the synthetic realm and present an approach that allows two incompatible transition metal catalyzed transformations to proceed in one pot in tandem. The key is the site isolation of both catalysts through compartmentalization using a core-shell micellar support in an aqueous environment. The support is based on amphiphilic triblock copolymers of poly(2-oxazoline)s with orthogonal functional groups on the side chain that can be used to cross-link covalently the micelle and to conjugate two metal catalysts in different domains of the micelle. The micelle core and shell provide different microenvironments for the transformations: Co-catalyzed hydration of an alkyne proceeds in the hydrophobic core, while the Rh-catalyzed asymmetric transfer hydrogenation of the intermediate ketone into a chiral alcohol occurs in the hydrophilic shell.
Assuntos
Polímeros/química , Catálise , Micelas , Espectroscopia de Prótons por Ressonância MagnéticaRESUMO
Rh(III)-TsDPEN, an immobilized analog of the well-known [Cp*Rh(bpy)(H(2)O)](2+) was evaluated as a heterogeneous, recyclable regeneration catalyst for reduced oxidoreductase cofactors [NAD(P)H]. Repeated use of this catalyst was established and the catalytic properties were initially investigated. Apparently, Rh(III)-TsDPEN is prone to severe diffusion limitations, necessitating further developments. Overall, a promising concept for chemoenzymatic redox catalysis is proposed, which may overcome some of the current limitations such as catalyst cost and incompatibility of Rh with some biocatalysts.