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DOI: 10.1055/s-0028-1087733
[Silica]-SMAP-Rh System for the Hydrosilylation of Hindered Ketones
Rezensent(en):Yasuhiro Uozumi, Yoichi M. A. Yamada, Hidetoshi OhtaHokkaido University, Sapporo and International Christian University, Tokyo, Japan
Synthesis of Silica-Supported Compact Phosphines and Their Application to Rhodium-Catalyzed Hydrosilylation of Hindered Ketones with Triorganosilanes
Organometallics 2008, 27: 6495-6506
Publikationsverlauf
Publikationsdatum:
19. Februar 2009 (online)
Key words
silica-gel support - phosphines - rhodium - hydrosilylation
Significance
Silica gel-supported SMAPs, [silica gel 60N]-SMAP (4A) and [CARiACT Q-10]-SMAP (4B), consisting of a compact trialkylphosphine (SMAP) were prepared. Thus, the reaction of Ph-SMAP (1) with TfOH afforded silyl triflate 2. Surface treatment of silica gel 60N and CARiACT Q-10 with 2 gave phosphine-functionalized silica gels 3A and 3B. The surface silanols were end-capped with Me3Si group to afford 4A and 4B. Hydrosilylation of ketones 5a-i with triorganosilanes 6a-c was carried out in the presence of [RhCl(C2H4)2]2 and 4A or 4B to give the silyl ethers 7 (27 examples, 91-100% yield).
Comment
Catalysts 4A and 4B were recovered by filtration and reused six and five times without any loss of catalytic activity, respectively. The leaching of Rh was checked by ICP-AES analysis, and determined to be <0.1%. The complexation reactions of 4A and 4B with [RhCl(cod)]2 afforded [silica gel 60N]-[(SMAP)-RhCl(cod)] and [CARiACT Q-10]-[(SMAP)-RhCl(cod)], respectively. These structures were confirmed by ¹³C, ³¹P CP/MAS NMR spectra and XAFS. The data demonstrate the formation of mono(phosphine)-Rh(I) complexes. The authors believe that such species facilitate the reaction of hindered ketones.