use of polystyrene resin anchored carbohydrates as asymmetric media in grignard reaction with ketones

ABSTRACT

It has been demonstrated that chiral products can be formed in reactions between achiral Grignard reagents and aldehydes or ketones in optically active solvents or in a solvent that contains an optically active substance. Generally, the stereos electivity of such reactions is low. Inch et al have observed that in the presence of suitably substituted carbohydrate, e.g., 1,25,6-di-O-isopropyUdeno-a-D-glucofuranose [I], Grignard-ketone [RMgBr - R'COR"] reactions can yield products with optical yields as high as 70 percent. On the other hand, he found that the Grignard-ketone reaction, C6H5MgBr -CH3COC2H5 in presence of the sugar derivative I, afforded the asymmetric carbinol, C6H5C[OH] [CH3]C2H5, with an optical yield of 10 percent. Accordingly, in this work we wish to report the Grignard-ketone reaction in the presence of a polymer anchored glucofuranose derivative II in order to improve the optical yield of the carbinol produced. The main reasons for using this polymer anchored sugar derivative II are the easy separation from the reaction medium and the possibility to use it for other reactions