Abstract
Chiral diphosphites and phosphinite-phosphites derived from spiro[4.4]nonane-1,6-diol were synthesized. Using Rh[I]– 7 complex in asymmetric hydroformylation of styrene, high regioselectivity (97%) and moderate enantioselectivity (65% ee) have been obtained. This catalyst system was also effective for aryl-substituted olefins. The diphosphites 8 and 9 bearing 1,1′-binaphthyl backbones were tested and the opposite configuration of the product indicates that the sense of enantioface selection is mainly dictated by the configuration of the terminal groups. Phosphinite–phosphite ligands gave low enantiomeric excesses (up to 48% ee) and low b/ n ratios. These results suggest that the regio- and enantioselectivity is mainly affected by the bulky substituents on terminal groups. The crystal structure of Rh( 7)(acac) are presented. The distortion in the structure is indicative of a crowded rhodium center.
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