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Silica chloropropyl

A solution of the lithium amide of 2,2,6,6-tetramethylpiperidine was prepared by the addition of 20 mL of 2.6 M butyllithium in hexane to a well stirred hexane solution of the piperidine in 100 mL hexane, under an atmosphere of He. The reaction was exothermic, formed a white solid precipitate, and was allowed to continue stirring for a few min. There was then added 6.5 g 2,5-dimethoxphenyl 3-chloropropyl sulfide, and a strongly exothermic reaction ensued. This was stirred for 30 min and then poured into dilute H2S04 (the progress of the reaction must be followed by TLC, silica gel plates, CH2Cl2 petroleum ether50 50to determine when... [Pg.66]

A mixture of 2.3 parts of l-(3-chloropropyl)-l,3-dihydro-2H-benzimidazol-2-one, 2.5 parts of 5-chloro-l,3-dihydro-l-(4-piperidinyl)-2H-benzimidazol-2-one, 3.2 parts of sodium carbonate, 0.1 part of potassium iodide and 80 parts of 4-methyl-2-pentanone is stirred and refluxed for 24 hours. The reaction mixture is cooled to room temperature and water is added. The undissolved product is filtered off and purified by column chromatography over silica gel using a mixture of trichloromethane and 10% methanol as eluent. The pure fractions are collected and the eluent is evaporated. The residue is crystallized from 4-methyl-2-pentanone. The product is filtered off and recrystallized from a mixture of N,N-dimethylformamide and water, yielding 1.3 parts (30%) of 5-chloro-l-[l-[3-(l,3-dihydro-2-oxo-2H-benzimidazol-l-yl)propyl]-4-piperidinyl]-l,3-dihydro-2H-benzimidazol-2-one MP 242.5°C. [Pg.1382]

Bis[2-benzoyloxy-3-chloropropyl] Ditellurium1 In a 250 ml separatory funnel are placed 0.80 g (1.85 mmol) of 2-benzoyloxy-3-chloropropyl tellurium trichloride, 40 ml of dichloromethane, and 30 ml of 20% (w/v) aqueous sodium sulfide nonahydrate solution. The mixture is shaken until all solids have dissolved, the organic layer is separated, dried, and the solvent evaporated. The product is purified by passing it through a short column of silica with dichloromethane as the mobile phase. The orange-red colored fractions are evaporated to leave a red oil yield 0.48 g (80%). [Pg.267]

Scheme 2 Preparation of catalysts by nucleophilic displacement of chloropropyl silicas. Scheme 2 Preparation of catalysts by nucleophilic displacement of chloropropyl silicas.
Silsesquioxanes of Mixed Functionality -Octa[(3-chloropropyl)-/ipropyl-silsesquioxanes] and Octa[(3-mercaptopropyl)- propyl-silsesquioxanes] as Models of Organomodified Silica Surfaces... [Pg.685]

Spherical siloxanes (RSiOi 5), with polyhedral frameworks, also called silsesquioxanes, can be used as defined oligomeric models for surface-modified silica gels or polysiloxanes. Whereas silsesquioxanes with alkyl-, aryl-, hydrido-, and trimethylsiloxy groups are known for a long time [1], functionalized octa-[propyl-silsesquioxanes], [X-(CH2)3]g(SiOi.5)g, were synthesized for the first time in 1990 by Weidner, Zeller, Deubzer, and Frey [2]. Octa[(3-chloropropyl)-silsesquioxane], [Cl-(CH2)3]g(SiO, 5)g, could be obtained by hydrolysis of (3-chloropropyl)-trichlorosilane. [Pg.691]

However, more interesting from an application point of view are silylation reactions which introduce new functions into the materials. These can be created either directly or in subsequent further steps after silylation. Most simple is the direct conversion of the silica to a basic material by reaction, for instance, with 3-aminopropyltriethoxysilane [17]. Also two-step processes have been employed to synthesize basic materials, where first chloropropyl groups are anchored to the surface with subsequent conversion of the chloro group into an amine. In order to remove the residual, unreacted silanol groups, a second silylation with hexamethyldisilazane can be used. Such materials were found to be reasonably active in different base-catalyzed reactions, such as Knoevenagel condensations and Michael additions. A survey of the catalyzed reactions and the types of modification used can be found in Ref. [5]. [Pg.862]

Soai et al. [62a] first reported the use of sihca gel or alumina as a heterogeneous support for chiral catalysts in the enantioselective addition of dialkylzincs to aldehydes. Chiral N-alkyhrorephedrines (R = Me, Et, n-Pr) were immobilized covalently on (3-chloropropyl)silyl-functionalized alumina or silica gel via a nucleophilic substitution. However, the catalytic activities and enantioselectivities were only moderate (24—59% ee) in comparison with those of homogeneous and polymer-... [Pg.58]

Tetramethylguanidine (TMG) 84 was supported on mesoporous silica according to the methodology depicted in Scheme 3.24, involving the nucleophilic substitution of the chloropropyl moiety anchored to silica (83) by TMG (84) in the presence of the strong basic TBD that was necessary to remove the formally produced hydrochloric acid. [Pg.132]

The second route (route b) involves the first easy preparation of the TMG substituted trimethoxysilane 80 starting from teiramethylguanidine 46 and (3-chloropropyl)tri-methoxysilane 66 [32] and the sub.sequent grafting onto both Kieselgel-60 71 and MTS 72. In contrast to the other catalysts these materials (81 and 82) have exposed silica surfaces. [Pg.150]

The eta-modified sihca was prepared by reacting the 3-chloropropyl silica with eta by using the same procedure used to the synthesis of eta complex. [Pg.13]

Table II presents a series of mixed-mode phases syn esiz by varying the ratio of n-octyldimethylsilane and 3-chIoropropyldimethylsitane. When comparing the mole ratio of added 3-chloropropyl methyIsilane and n-oc-tyldimethylsilane to the actual mole ratio bonded onto the silica gel, the 3-chloropropyldimethylsilane was shown to bond three times faster than the n-octyldimethylsilane. Once the relative bonding rates of these silanes are known, the silane ratio required to produce a desired ligand ratio can be easily controlled. Subsequently, a wi range of stationary-phase retention behavior becomes available from relatively simple bonding chemistry. Total surface coverages (moles of ligand per gram of silica gel) for these four phases... Table II presents a series of mixed-mode phases syn esiz by varying the ratio of n-octyldimethylsilane and 3-chIoropropyldimethylsitane. When comparing the mole ratio of added 3-chloropropyl methyIsilane and n-oc-tyldimethylsilane to the actual mole ratio bonded onto the silica gel, the 3-chloropropyldimethylsilane was shown to bond three times faster than the n-octyldimethylsilane. Once the relative bonding rates of these silanes are known, the silane ratio required to produce a desired ligand ratio can be easily controlled. Subsequently, a wi range of stationary-phase retention behavior becomes available from relatively simple bonding chemistry. Total surface coverages (moles of ligand per gram of silica gel) for these four phases...
The usefulness of this material for the immobilization of various species was shown and compared to that of the ordered mesoporous silicas containing chloropropyl groups. [Pg.303]

Although the above-mentioned binding pH has been reduced to 5.0, there is still an apparent gap for the direct application to urine because the pH of frequently used biosamples, particularly urine, ranges from 4.5 to 8.0. " Liu and co-workers further synthesized a pyridinylboronic acid-functionalized organic-silica hybrid monolithic capillary " to meet the broad pH range of urine samples. The preparation procedure is illustrated in Scheme 11.11. It included two steps (1) preparation of a chloropropyl-silica hybrid... [Pg.320]

Perhaps the best evidence for the superior quality of the composite comes from our comparative studies with other polyamine composites and polystyrene resins. Ramsden et al. synthesized a silica-polyamine composite by reacting 3-chloropropyl trimethoxy silane with PEI, and then reacting the resulting polyamine silane with silica gel. We reproduced this synflietic approach with the same silica used in our pro-cedme (Fig. 1). The material produced had a density of 0.31 g/mL versus 0.49 g/mL for WP-1. A scanning electron micrograph of the two materials revealed a much smoother surface for WP-1 relative to the material produced by the method of Ramsden (Fig. 4). [Pg.58]

Figure 3 C-NMR CP-MAS of the aliphatic region of silica gel silanized with 3-chloropropyl silane with hydration, (A) and without hydration, (B) showing the methoxyl peak intensity. Figure 3 C-NMR CP-MAS of the aliphatic region of silica gel silanized with 3-chloropropyl silane with hydration, (A) and without hydration, (B) showing the methoxyl peak intensity.
Furthermore, the modified chain ends can also be directly bonded onto the surfaces, an approach that was followed by Liu et al. [40]. The synthesis started with an anionic polymerized polystyrene that was reacted with (3-chloropropyl) trimethoxysilane (Scheme 20). The obtained silane end groups enabled the attachment onto silica nanoparticles, to achieve inorganic Si02 nanoparticles in organic polystyrene matrices. [Pg.147]

In the case of the co-condensation method, CPTES is introduced into the mesoporous silica during the sol-gel process, and the functionalization of the chloropropyl group onto the support is done through co-condensation reaction. [Pg.95]


See other pages where Silica chloropropyl is mentioned: [Pg.68]    [Pg.136]    [Pg.197]    [Pg.691]    [Pg.301]    [Pg.245]    [Pg.970]    [Pg.78]    [Pg.528]    [Pg.74]    [Pg.175]    [Pg.189]    [Pg.302]    [Pg.303]    [Pg.286]    [Pg.28]    [Pg.215]    [Pg.788]    [Pg.788]    [Pg.463]    [Pg.57]    [Pg.61]    [Pg.95]   
See also in sourсe #XX -- [ Pg.197 ]




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2- -3-chloropropyl

Chloropropylate

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