DENDRITIC STYRYL TADDOLS AS NOVEL POLYMER CROSS-LINKERS - FIRST APPLICATION IN AN ENANTIOSELECTIVE ET2ZN ADDITION MEDIATED BY A POLYMER-INCORPORATED TITANATE

TADDOLs a',alpha'-tetraaryl-1,3-dioxolane-4,5-dimethanols) with dendri tic branches attached to the aryl groups and with 8 or 16 peripheral s tyryl double bonds have been synthesized (4 and 5). With these compoun ds, dendritic molecules were employed for the first time as cross-link ers in a polymerization. The resulting polystyrene was loaded with tit anate (Ti(OCHMe2)(4)) to generate polymer beads incorporating Ti-TADDO Late centers (Figs. 1 and 2) for enantioselective catalysis (Et2Zn add ition to PhCHO). Compared with conventionally polymer-attached, insolu ble Ti-TADDOLates (cf. 3), the new materials have a much higher cataly tic activity, rather close to that of soluble analogs (Fig. 3).