25186-18-9Relevant academic research and scientific papers
Convenient methods for the synthesis of a library of hemilabile phosphines
Jimenez, M. Victoria,Perez-Torrente, Jesus J.,Bartolome, M. Isabel,Oro, Luis A.
experimental part, p. 1916 - 1922 (2009/12/28)
A series of novel functionalized phosphines of hemilabile character, R 2P(CH2)nZ, have been prepared from diarylphosphines using several synthetic methodologies. The synthetic methods include the alkylation of lithium diar
Ligand Electronic Effects in Asymmetric Catalysis: Enhanced Enantioselectivity in the Asymmetric Hydrocyanation of Vinylarenes
Casalnuovo, Albert L.,RajanBabu, T. V.,Ayers, Timothy A.,Warren, Timothy H.
, p. 9869 - 9882 (2007/10/02)
The enantioselectivity of the nickel-catalyzed, asymmetric hydrocyanation of vinylarenes using glucosederived, chiral phosphinite ligands, L, increases dramatically when the ligands contain electron-withdrawing P-aryl substituents.The substrate and solvent also strongly influence the enantioselectivity, with the highest ee's (85-91percent for 6-methoxy-2-vinylnaphthalene (MVN)) obtained for the hydrocyanation of electron-rich vinylarenes in a nonpolar solvent such as hexane.Mechanistic studies suggest the catalytic cycle consists of an initial HCN oxidative addition or vinylarene coordination to "NiL", followed by insertion to form an (η3-benzyl)nickel cyanide complex, and irreversible reductive elimination of the nitrile.A kinetic analysis of the NiLa(COD) (La, P-aryl=3,5-(CF3)2C6H3) catalyzed hydrocyanation of MVN indicates that as the HCN concentration is increased the catalyst resting state shifts from NiLa(COD) to a complex containing both MVN and HCN, presumably the (η3-benzyl)nickel cyanide intermediate NiLa(η3-CH3CHC10H6OCH3)CN.A 31P NMR analysis of the intermediate NiLa(MVN) shows little ground state differentiation of the MVN enantiofaces and suggests that the enantioselectivity is determined later in the mechanism.Deuterium labeling studies suggest that electron-withdrawing P-aryl substituents increase the rate of reductive elimination of the product nitrile from the (η3-benzyl)nickel cyanide intermediate and, on this basis, a rationale for the ligand electronic effect is proposed.
