Polymer-supported scandium catalyst

A partially soluble polyallylscandium triflamide ditriflate 45 was prepared and used to catalyze a three-component coupling reaction.67 An aldehyde, an aromatic amine, and an alkene were mixed in the presence of the catalyst to afford tetrahydroquinolines (equation 17). The catalyst was recovered from the reaction mixtures by precipitation with hexane and could be recycled without loss of activity. Another polymer-supported scandium catalyst was prepared by treating Nafion with scandium chloride to afford the Nafion-scandium catalyst 46.68 This catalyst was used in allylation reactions of carbonyl compounds by tetraallyltin (equation 18). It could be easily recovered by filtration and reused without appreciable loss of activity. 

Kobayashi, S. Nagayama, S. A New Methodology for Combinatorial Synthesis. Preparation of Diverse Quinoline Derivatives Using a Novel Polymer-Supported Scandium Catalyst, J. Am. Chem. Soc. 1996, 118, 8977. 

Kobayashi and Nagayama [26] have reported the preparation of a library of quinoline derivatives using a novel polymer-supported scandium catalyst (Fig. 8) in a three-component coupling reaction. The scandium catalyst has the advantage of being partially soluble in the dichloromethane/acetonitrile mixtures but can be precipitated by the addition of hexanes and thus be removed quantitatively by filtration. 

Kobayashi S, Nagayama S, A new methodology for combinatorial synthesis. Preparation of diverse quinoline derivatives using a novel polymer-supported scandium catalyst, J. Am. Chem. Soc., 118 8977-8978, 1996. 

Recently, scandium triflate [Sc(OTf)3] was found to be stable in water and successful Lewis acid catalysis was carried out in both water and organic solvents [6-8]. Sc(OTf)3 coordinates to Lewis bases under equilibrium conditions, and thus activation of carbonyl compounds using a catalytic amount of the acid has been achieved [6,7]. In addition, effective activation of nitrogen-containing compounds such as imines, amino aldehydes, etc. has been performed successfully [8]. Encouraged by the characteristics and the usefulness of Sc(OTf)3 as a Lewis acid catalyst, a polymer-supported scandium catalyst was prepared. 

Synthesis of a quinoline library using a polymer-supported scandium catalyst... 

Hydrophobic polymer-supported scandium catalyst has been developed by Kobayashi, which is highly active for carbon-carbon bond-forming reactions in water. Organic reactions in water without the use of any harmful organic... 

In another procedure, the preparation of the polymer-supported scandium catalyst was performed according to Scheme 8.17 [70], Polystyrene, cross-linked with divinylbenzene, was treated with 5-phenylvaleryl chloride in carbon disulfide in the presence of aluminum trichloride. The carbonyl groups were then reduced using aluminum trichloride-lithium aluminum hydride in diethyl ether to afford double spacer resin. After sulfonation (chlorosulfonic acid/acetic acid), resin was treated with scandium(III) chloride in acetonitrile at room temperature to give the polymer-supported scandium chloride. Finally, it was treated with trifluo-romethanesulfonic acid to afford the immobilized triflate. 

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