Asymmetric hydroformylation catalyzed by rhodium(I) complexes of novel chiral spiro ligands

Chiral diphosphites and phosphinite-phosphites derived from spiro[4.4]nonan e-1,6-diol were synthesized. Using Rh[I]-7 complex in asymmetric hydroformy lation of styrene, high regioselectivity (97%) and moderate enantioselectiv ity (65% ee) have been obtained. This catalyst system was also effective fo r aryl-substituted olefins. The diphosphites 8 and 9 bearing 1,1'-binaphthy l backbones were tested and the opposite configuration of the product indic ates that the sense of enantioface selection is mainly dictated by the conf iguration of the terminal groups. Phosphinite-phosphite ligands gave low en antiomeric excesses (up to 48% ee) and low b/n ratios. These results sugges t that the regio- and enantioselectivity is mainly affected by the bulky su bstituents on terminal groups. The crystal structure of Rh(7)(acac) are pre sented. The distortion in the structure is indicative of a crowded rhodium center. (C) 1999 Elsevier Science S.A. All rights reserved.