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.
Key words
electrophilic additions - combinatorial chemistry - acylations - silica - scavengers
References
<A NAME="RD17102ST-1">1 </A>
Ley SV.
Baxendale IR.
Bream RN.
Jackson PS.
Leach AG.
Longbottom DA.
Nesi M.
Scott JS.
Storer RI.
Taylor SJ.
J. Chem Soc., Perkin Trans 1
2000,
3815
<A NAME="RD17102ST-2">2 </A>
Booth RJ.
Hodges JC.
Acc. Chem. Res.
1999,
32:
18
<A NAME="RD17102ST-3">3 </A>
Cresswell MW.
Bolton GL.
Hodges JC.
Meppen M.
Tetrahedron
1998,
54:
3983
<A NAME="RD17102ST-4">4 </A>
Parlow JJ.
Flynn DL.
Tetrahedron
1998,
54:
4013
<A NAME="RD17102ST-5">5 </A>
Booth RJ.
Hodges JC.
J. Am. Chem. Soc.
1997,
119:
4882
<A NAME="RD17102ST-6">6 </A>
Sherrington DC.
Chem.
Commun.
1998,
2275
<A NAME="RD17102ST-7">7 </A>
Macquarrie DJ.
J.
Chem. Soc., Chem. Commun.
1996,
1961
<A NAME="RD17102ST-8">8 </A>
Macquarrie DJ.
Jackson DB.
Mdoe JEG.
Clark JH.
New
J. Chem.
1999,
23:
539
<A NAME="RD17102ST-9">9 </A>
Elings JA.
Ait-Meddour R.
Macquarrie DJ.
Clark JH.
Chem.
Commun.
1998,
2707
<A NAME="RD17102ST-10">10 </A>
Lambert A.
Elings JA.
Macquarrie DJ.
Carr G.
Clark JH.
Synlett
2000,
1052
<A NAME="RD17102ST-11">11 </A>
Clark JH.
Elings SA.
Wilson K.
C.
R. Acad. Sci.
2000,
3:
399
<A NAME="RD17102ST-12">12 </A>
Macquarrie DJ.
Green
Chem.
1999,
1:
195
<A NAME="RD17102ST-13">13 </A>
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
<A NAME="RD17102ST-14">14 </A>
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.
