Journal
CHEMISTRY-AN ASIAN JOURNAL
Volume 14, Issue 9, Pages 1496-1505Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/asia.201900043
Keywords
cascade reactions; cyclopropanic derivatives; heterogeneous catalysis; periodic mesoporous organosilicas
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Funding
- National Natural Science Foundation of China [51472062]
- Opening Project of Key Laboratory of Polyoxometalate Science of Ministry of Education
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In this work, three organosilica precursors functionalized with carbamate moieties were synthesized by condensing of 3-isocyanatopropyltriethoxysilane and coupling regents of either hydroquinone (HQ), bisphenol A (BPA), or 1,1-bi-2-naphthol (BN). These organosilica precursors were covalently bonded in the framework of periodic mesoporous organosilicas by co-condensation and hydrolysis with tetraethyl orthosilicate (TEOS) under hydrothermal treatment. The compositions and physical properties were characterized with FTIR, XRD, thermogravimetric/differential thermal analysis (TG/DTA), (SiNMR)-Si-29, (CNMR)-C-13 spectroscopies, SEM, TEM, and BET technologies. These characterizations suggest that three different structures were formed as the result of different sizes and compositions of the organosilica precursors. The three mesoporous organosilicas were applied as heterogeneous catalysts in the one-pot cascade Knoevenagel and Michael cyclopropanic reactions for the synthesis of cyclopropanic derivatives and showed excellent activity and selectivity. The highest conversion was obtained with mesoporous catalyst (MC)-HQ owing to its ordered mesostructure, highest surface area, and weakest stereo effect of the organic linking groups compared with MC-BAP and MC-BN. This methodology employed cheaper and more easily obtainable raw materials as reagents over the traditional alkene additive system and these heterogeneous catalysts exhibit superior performance and recyclability than typical homogeneous organic catalysts.
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