Immobilization of Organic Catalysts: When, Why, and How

Abstract

This review article is divided in two parts. In the first part (Sections 2 and 3) selected examples of the publications that appeared in the literature in the period 2003–2005 in the field of immobilized organic catalysis are presented. When appropriate, the results of these publications are compared to those reported earlier and already discussed in a previous review article (see ref. 4). On the basis of this survey, in Section 4 some general considerations about when and why a supported version of an organic catalyst is worth developing are proposed. In Section 4 a list of suggestions about how the process of immobilization should be carried out is also included, taking into account several factors such as the properties of the catalyst, the nature of the support, and the mode of connection of the catalyst to the support.

Novel Prolinamide‐Supported Polystyrene as Highly Stereoselective and Recyclable Organocatalyst for the Aldol Reaction

“…[2] Immobilization of organocatalyst to the support can be realized both with a non-covalent linkage [3] or with a covalent linkage on supports such as polystyrene, [4] silica, [5] PEG, [6] magnetite [7] or ionic liquids. [8] Recently, the immobilization of l-proline on polystyrene has received interest, and indeed stereoselective and recyclable materials have been prepared.…”

Asymmetric organocatalysts supported on vinyl addition polynorbornenes for work in aqueous media

“…2 The catalytic activity of polymersupported species is importantly determined by the accessibility of the catalytic sites to the reactants, and is modulated by mass transfer limitations In this respect, different features of polymeric supports, such as solubility/swellability profile, degree of functionalization and the possible involvement of the polymer backbone in the catalytic reaction need all to be considered. 3 The choice of polymeric support is therefore an essential issue, since its structure and properties can importantly influence the course of chemical reactions mediated by catalysts immobilized on it. As a matter of fact, no single polymer structure would be optimal for every conceivable synthetic application.…”

Inserção C-H de carbenóides de ródio em água e reutilização do catalisador

“…Entre estes métodos, a integração de solventes não voláteis (polietilenoglicol (PEG) 26 ou líquidos iónicos) 27 com técnicas de extracção com solventes orgânicos ou dióxido de carbono super-crítico (scCO 2 ) 28 encontram-se entre os métodos mais populares, no entanto, existem ainda inúmeras outras possibilidades, como a utilização de água 29 , solventes fluorados 30,31 , sistemas sem solvente 32,33 e sistemas com o catalisador imobilizado num suporte 34 . Diversos estudos onde se utilizou a água como meio reaccional indicam que a água tem enormes potencialidades para ser utilizada para este fim numa multiplicidade de reacções, sendo mesmo uma das melhores escolhas em termos de menor impacto ambiental e económico 29,[35][36][37][38] .…”