Royal Society of ChemistryGarcía García, P.; Zagdoun, A.; Coperet, C.; Lesage, A.; Díaz Morales, UM.; Corma Canós, A. (2013). In situ preparation of a multifunctional chiral hybrid organic-inorganic catalyst for asymmetric multicomponent reactions. Chemical Science. 4 (5) A chiral mesoporous organosilica material incorporating a urea based-cinchona derivative and propylamine groups was prepared by a co-condensation method. The multisite solid catalyst efficiently promoted the asymmetric multicomponent reaction of aldehydes, malonates and nitromethane.10 IntroductionMulticomponent reactions are the most efficient chemical procedures for the synthetic preparation of organic compounds.
1-3This approach is particularly attractive as it enables the production of highly elaborated compounds from raw materials in 15 an economical, energy-saving, and intensified manner, avoiding intermediate purification steps. Asymmetric multicomponent reactions 4 are of growing interest and their potential have been recently expanded by the introduction of chiral small organic molecules as highly efficient catalysts. 5 In this regard, and as far 20 as we know, all of the developed methodologies make use of homogeneous catalysts and many of them involve nucleophilic addition to an in situ formed imine. 6 Another strategy exploits the ability of chiral amine catalysts to combine two modes of catalytic activation of carbonyl compounds (iminium and 25 enamine catalysis) easing highly enantioselective Michael-type multicomponent processes. 7-9 Some other multicomponent reactions mediated by chiral homogeneous organocatalysts have been reported. [10][11][12][13] In the domain of catalyst mediated reactions, heterogeneous 30 catalysis is often preferable to homogeneous catalysis because of the easy separation of the catalyst from the reaction medium and reuse. Furthermore, solid catalysts are specially suited for the design of continuous stirred-tank reactor (CSTR) or fixed bed continuous flow processes.14 The extraordinary pace of 35 innovation and progress in asymmetric homogeneous catalysis contrasts profoundly with asymmetric heterogeneous procedures. A commonly used strategy in asymmetric heterogeneous catalysis involves the heterogeneization of a successful homogeneous catalyst by covalent linkage to an inorganic oxide support or 40 organic polymer. It is frequently observed that the new solid catalyst exhibits lower performance compared to the homogeneous counterpart in terms of activity, selectivity and enantioselectivity. Therefore, the development of asymmetric heterogeneous catalyzed procedures is an active area of research 45 that can be of particular interest if one could achieve highly enantioselective reactions. Nevertheless, the use of chiral solid catalysts has been limited to two component reactions and applications to asymmetric multicomponent procedures have been elusive. Here we report our approach towards meeting this challenge. Specifically, the 60 unprecedented application of a chiral heterogeneous catalyst in the e...