REGIO-AND STEREOSELECTIVE HYDROFORMYLATION OF GLUCAL DERIVATIVES WITHRHODIUM CATALYSTS

The hydroformylation of the differently protected glucal derivatives 3 ,4,6-tri-O-acetyl-D-glucal, 3,4,6-tri-O-benzyl-D-glucal and 3,4,6-tri- O-methyl-D-glucal was carried out with rhodium catalytic systems, and 2-formyl derivatives were obtained as the main products in yields of 5 8%, 68%, and 55% respectively, when [Rh-2(mu-OMe)(2)(COD)(2)]/P(O-o-(B uC6H4)-Bu-t)(3) was used. The bulky phosphite needs to be used as auxi liary ligand to achieve the hydroformylation of these highly hindered cyclic olefins. A mechanistic cycle is proposed which explains the reg io- and stereoselectivity of the reaction. The mononuclear rhodium com plex trans-[RhCl(CO)(P(O-o-(BuC6H4)-Bu-t)(3))(2)] was isolated at the end of the catalytic reaction by breaking the dinuclear complexes used as catalyst precursors. To confirm the characterization of trans-[RhC l(CO)(P(O-o-(BuC6H4)-Bu-t)(3))(2)], a eparate synthesis was carried ou t which is elated crystals suitable for an X-ray determination.