Synlett 2003(2): 0244-0246
DOI: 10.1055/s-2003-36778
LETTER
© Georg Thieme Verlag Stuttgart · New York

High-Loading Aminopropyl Silicas as Novel Scavenger Resins for High Throughput Synthesis

Duncan J. Macquarrie*, Hélène Rousseau
Department of Chemistry, University of York, Heslington, York, YO10 5DD, England, U.K.
Fax: +44(1904)434550; e-Mail: djm13@york.ac.uk;
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Publikationsverlauf

Received 1 August 2002
Publikationsdatum:
22. Januar 2003 (online)

Abstract

High loading amino- and diamino-functionalised silicas were prepared by a simple method; the resultant materials have been shown to be excellent high capacity scavengers for three representative types of electrophile with a wide solvent compatibility.

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The materials prepared were made by the templated co-condensation of tetraethoxysilane (TEOS) and a second functional amine[7], either 3-aminopropyltrimethoxysilane 1 or N-(2′-aminoethyl)-3-aminopropyltrimethoxysilane 2. The proportion of the functional silane was kept as high as possible, commensurate with a high yield of the desired solid product [50 mol% RSi(OMe)3: 50 mol% TEOS in the case of 1, 33 mol% RSi(OMe)3: 67 mol% TEOS in the case of 2]. The two silanes were added together but separately (in each case a total of 0.1 mol of silane was added) to a mixture of water, ethanol (50 mL of each) and 1-aminododecane (5.1 g) at room temperature. After stirring for 18 h, the white suspension was filtered and the resultant solid was extracted using a Soxhlet extractor and ethanol as extractant for 12 hours. The extracted solids were dried at 100 °C to remove solvent, and were stored in screwtop jars. Yield is typically 10 g. These procedures gave materials with loadings of 5 mmolg-1 aminopropyl(3) and 3.7 mmolg-1 of the diaminosilane respectively(4) (Scheme [1] ).

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These materials were then evaluated as scavengers by stirring them with an excess (a mole ratio of 2:1 electrophile: amine group was used) of electrophiles (phenyl isocyanate 5, benzenesulfonyl chloride 6, and benzoyl chloride 7) in a range of solvents. For 1 g of scavenger 5 mL of solvent was used. After 5 hours, the solids were removed by filtration, washed with the solvent used in the reaction, and the quantity of electrophile remaining in solution was calculated from GC with n-dodecane as internal standard.