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Synfacts 2008(3): 0320-0320  
DOI: 10.1055/s-2008-1042668
Polymer-Supported Synthesis
© Georg Thieme Verlag Stuttgart · New York

Silica-Supported Palladium Catalysts for Aldol Reaction

Contributor(s): Yasuhiro Uozumi, Yoichi M. A. Yamada
N. C. Mehendale, J. R. A. Sietsma, K. P. de Jong, C. A. van Walree, R. J. M. Klein Gebbink, G. van Koten*
Utrecht University, The Netherlands
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Publication History

Publication Date:
21 February 2008 (online)

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Significance

ECE-pincer Pd(II) complexes (ECE = [C6H3(CH2E)2-2,6]-, E = PPh2 and SPh) immobilized on mesoporous silicas were designed, prepared, and used for the aldol reaction as heterogeneous catalysts. Thus, surface grafting of 1 and 2 onto the ordered mesoporous silica SBA-15 or MCM-41 was carried out in toluene at 90 °C for 20 h to give SBA-15-supported 3 and MCM-41-supported 4, respectively. Silica 3 was treated with HMDS to afford 5 where the remaining unreacted silanol groups were capped with TMS. The aldol reaction of 6 and 7 (1 mol equiv) was catalyzed by 5 to give oxazolines 8 and 9. The catalyst 5 was reused without significant loss of catalytic activity while leaching of Pd was observed (96-348 ppm).