Carreira Monica, Contel Maria
Department of Chemistry, Brooklyn College, The City University of New York, Brooklyn, NY 11210, USA.
Top Curr Chem. 2012;308:247-73. doi: 10.1007/128_2011_239.
In this review, we describe the papers and patents dealing with the fluorous biphasic system (FBS) hydrosilylation reactions reported to date. Despite the limited number of reports, the FBS hydrosilylation reaction has been extremely successful. In all cases fluorous monophosphines (either alkylic or perfluoroalkylsilyl-substituted derivatives of triphenylphosphine) have been employed as ligands to synthesize and inmobilize the metal catalysts (either rhodium(I) or gold(I) derivatives) in the fluorous solvent (including a fluorous ionic liquid). The hydrosilylation of alkenes, ketones and enones with fluorous rhodium analogs to the Wilkinson's catalyst [RhCl(PPh(3))(3)], have afforded high TON/TOF and a very efficient separation and recycling of the fluorous catalyst. Modification of the fluorous content and position of the fluorous tails in the aryl groups of the phosphines have allowed for further optimization of the process and a better recovery of the catalyst with minimal leaching of rhodium and fluorous ligand to the organic phase. Moreover, the use of the so-called second generation methods which eliminate the need of fluorous solvents by exploiting the temperature-dependent solubilities of fluorous catalysts in common organic solvents (thermomorphic properties) have permitted the use and separation of fluorous alkyl-phosphine rhodium catalysts in hydrosilylation reactions in conventional organic solvents. The addition of an insoluble fluorous support such as Teflon tape allowed for an exceptionally easy and efficient recovery of fluorous rhodium catalysts ("catalyst-on-a-tape") in the hydrosilylation of ketones. In the case of the FBS gold-catalyzed hydrosilylation of aldehydes, new fluorous gold catalysts with alkylic phosphines have led to an efficient separation and recycling of the gold catalysts although the TON/TOF are lower than in the rhodium-catalyzed hydrosilylation of alkenes and ketones. A detailed study of the non-fluorous gold-catalyzed version has helped to explain how this catalytic system could be improved.
在本综述中，我们描述了迄今为止报道的有关氟两相体系（FBS）硅氢化反应的论文和专利。尽管相关报道数量有限，但FBS硅氢化反应却极为成功。在所有案例中，氟代单膦（三苯基膦的烷基或全氟烷基硅基取代衍生物）都被用作配体，以在氟代溶剂（包括氟代离子液体）中合成并固定金属催化剂（铑（I）或金（I）衍生物）。烯烃、酮和烯酮与类似威尔金森催化剂[RhCl(PPh(3))(3)]的氟代铑类似物发生硅氢化反应，实现了高TON/TOF，并且氟代催化剂能够高效分离和循环利用。通过改变膦的芳基中氟含量和氟尾位置，可以进一步优化该过程，使催化剂得到更好的回收，同时铑和氟代配体向有机相的浸出量降至最低。此外，所谓的第二代方法利用氟代催化剂在常见有机溶剂中的温度依赖性溶解度（热致变性质），无需使用氟代溶剂，从而能够在传统有机溶剂中进行硅氢化反应时使用和分离氟代烷基膦铑催化剂。添加不溶性氟代载体（如聚四氟乙烯胶带），使得在酮的硅氢化反应中能够极其轻松高效地回收氟代铑催化剂（“胶带催化剂”）。在FBS金催化的醛硅氢化反应中，新型含烷基膦的氟代金催化剂实现了金催化剂的高效分离和循环利用，不过其TON/TOF低于铑催化的烯烃和酮硅氢化反应。对非氟代金催化版本的详细研究有助于解释如何改进该催化体系。
