C. Scriban, David S. Glueck, and James A. Golen
Feb 20, 2007
Citations
0
Influential Citations
47
Citations
Journal
Organometallics
Abstract
The catalyst precursor Pt((R,R)-Me-Duphos)(Ph)(Cl) (1) mediated asymmetric alkylation of the secondary phosphine PHMe(Is) (2; Is = 2,4,6-(i-Pr)3C6H2) with benzyl bromide in the presence of the base NaOSiMe3 to yield enantioenriched PMeIs(CH2Ph) (3). A mechanism for the catalysis has been proposed, on the basis of studies of the individual stoichiometric steps. The terminal phosphido complex Pt((R,R)-Me-Duphos)(Ph)(PMeIs) (4) was formed by proton transfer from 2 to the silanolate ligand in Pt((R,R)-Me-Duphos)(Ph)(OSiMe3) (5), which was generated from 1 (or from Pt((R,R)-Me-Duphos)(Ph)(Br) (7)) and NaOSiMe3. The silanolate complex 5 reacted with water to yield Pt((R,R)-Me-Duphos)(Ph)(OH) (6); both 6 and 7 were crystallographically characterized. The stoichiometric reaction of 4 and benzyl bromide in toluene gave the bromide 7 and 3. In more polar solvents these compounds were in equilibrium with the cation [Pt((R,R)-Me-Duphos)(Ph)(PMeIs(CH2Ph))][Br] (8-Br), the major Pt complex present during catalysis, whi...