Functionalized Silica Gels for Organic Synthesis

Supported Reagents – Functionalized Silica Gels for Organic Synthesis

• Bases and Acid Scavengers
• Oxidizing Reagents
• Phosphines
• Diols and Epoxides

Bases and Acid Scavengers

3-Amino-functionalized silica gel, Product No. 364258
Loading ca. 1.0 mmol N/g
This functionalized silica gel has been used for the separation and solid-phase extraction (SPE) of sugars, as well as for the separation of steroids, cholesterol, and triglycerides. It has also been used in size-exclusion chromatography of cationic polymers, as a scavenger to remove excess acid chlorides and as a catalyst in Knoevenagel reactions.

3-(1-Imidazol-1-yl)propyl- functionalized silica gel, Product No. 537950

Loading ca. 2.2 mmol N/g
This gel has been used for anchoring ruthenium complexes used in catalytic cyclization reactions and as a chromatographic packing for the separation of metal chelates.

3-(1-Morpholino)propyl-functionalized silica gel, Product No. 569798

Loading ca. 1.1 mmol N/g
This grafted morpholine silica gel is commonly used as an acid sponge. It is used in the same manner as morpholine functionalized polymers.

3-(1-Piperazino)propyl-functionalized silica gel, Product No. 552607

Loading ca. 1.9 mmol N/g
This silica-bound piperazine is a useful deblocking and scavenging agent for Fmoc and for the Bsmoc amino protecting group. According to the results of one study, silica-bound piperazine is superior to polystyrene-based reagents. It has also been used to immobilize metal carbonyl complexes, for the synthesis of 2-aminobutadienes, as a traceless linker in cross-coupling strategy starting with diazonium ions and as a solid-phase Knoevenagel catalyst.

2-(2-Pyridyl)ethyl-functionalized silica gel, Product No. 537985
Loading ca. 1.3 mmol/g
This gel can be used as a tertiary amine for acid removal. It can also be used to anchor Cu₂+ ions, which can then be used as a catalyst for hydroquinone oxidation.

3-(Trimethylammonium)propyl- functionalized silica gel-carbonate, Product No. 552887
Loading ca. 0.7 mmol/g
Can be used as a general base to scavenge acids.

Coupling Reagents

3-(1-Cyclohexylcarbodiimido)propyl- functionalized silica gel, Product No. 569887
Loading ca. 2.0 mmol N/g
Coupling reagent for peptide synthesis.

Oxidizing Reagents

Pyridinium chlorochromate, ca. 20 wt. % on silica gel, Product No. 569801
Used for the general oxidation of alcohols to carbonyl compounds, selective oxidation of allylic and benzylic alcohols, organometallic oxidation, oxidative transpositions, oxidative cleavages, allylic and benzylic oxidation, and oxidative cyclizations. Using PCC immobilized on silica gel provides anhydrous conditions that may otherwise promote side reactions and reduce yields. It greatly facili-
tates removal of polymeric reduced chromium by-products, and is compatible with acid-sensitive protecting groups. When used in conjunction with ultrasound, kinetics are increased and the amount of oxidant required to complete the reaction is decreased.

Pyridinium dichromate, ca. 20 wt. % on silica gel, Product No. 569828
Used as an alternative to PCC in nucleoside and carbohydrate oxidation, particularly for fragile molecules. Can also be used in conjunction with tert-butyl hydroperoxide for a variety of oxidative transformations. PDC-on-silica is a very convenient and effective reagent for oxidizing allylic and benzylic alcohols, as well as saturated primary and secondary alcohols and it is compatible with acid-sensitive groups, such as cyclopropane ring, or a ketal function.

Phosphines

2-(Diphenylphosphino)ethyl- functionalized silica gel, Product No. 538019

Loading ca. 0.7 mmol/g
Used for NiCl₂ and CoCl₂ complexation, chromatographic phase preparation, hydro-formylation of 1-heptene with silica-anchored rhodium thiolate complexes, cross-coupling reactions of organic halides with organotin and organomagnesium reagents with silica-supported palladium, and for carbonickel complex immobilization. Can also be used with a supported rhodium(I) catalyst for olefin catalytic reduction, with dinuclear rhodium(I) complexes for hydro-formylation reactions, with palladium(0) for cross-coupling organoboron compounds, and with organic halides or organic triflates.