selectivity of the reaction,' substituents on the ligating phosphorus had a more pronounced effect. Several examples of these ligands derived from @-phenyl glucoside and their respective selectivities are shown in Table I. From this study, we found that elec- tron-withdrawing substituents on phosphorus-linked aryl groups dramatically enhance the enantioselectivity. Such electronic effects of ligands on the enantioselectivity are rare, and as in the welldocumented case of Mn(II1)-mediated epoxidation reactions,' these may play an important role in the design of new catalysts. The highest enantioselectivities are obtained in nonpolar solvents (C6F6 = hexane > benzene > THF), while increasing the reaction temperature decreases the enantioselectivity. Other factors such as the extent of reaction, Ni to substrate ratio, and ligand to Ni ratio12 do not affect the observed enantioselectivity. Remarkably, the highly enantioselective 3,5-(CF3)2C6H3 cat- alyst derivative also exhibits very high activity in the hydro- cyanation of MVN. Catalytic activities as high as 552 turnover numbers/h (769 total) have been measured at 25 OC for the hydrocyanation of MVN using 0.13 mol % of this ligand and 0.1 mol % of Ni. By comparison, at 25 OC this catalyst is an order of magnitude more active than the commonly used NiP(p- OC6H4CH3)4 cataly~t.~*~ Using this catalyst, the naproxen pre- cursor (S)-(-)-6-methoxy-2-naphthalene2-propionitrile has been prepared in an optically pure form for the first time by recrys- tallization of the resulting product.' Even though the enantioselectivity of our system has been optimized only for the naproxen precursor, we briefly investigated the selectivity in a number of other vinylarenes in the presence of the diphenylphosphinite ligand (R = Ph; XY = OPh) and the corresponding bis(bis(trifluoromethyl)phenyl) phosphinite deriv- ative (R = 3,5-(CF3)2C6H3; XY = OPh). Listed below are the respective ee's for these ligands under our standard conditions: 4-isobutylstyrene, 10 and 50; 4-phenyl-3-fluorostyrene, 10 and 55; acenaphthylene, 0 and 59; 1-vinylnaphthalene, 63 and 68. In each case, the overall yield and the enantioselectivity with the electron-deficient phosphinite systems are unprecedented, and the unmistakable electronic effect on the ee has been confirmed.