作者:Emmanuel Robé、Carmen Ortega、Maciek Mikina、Marian Mikolajczyk、Jean-Claude Daran、Maryse Gouygou
DOI:10.1021/om0503646
日期:2005.11.1
The stereochemically dynamic 2,2'-biphospholes 8, 9, and 10 have been synthesized by asymmetric alkylation of 2,2'-biphospholyl anion with enantiomerically pure diol ditosylates. A good carbon-to-phosphorus induction has been obtained in particular in the case of compound 8. The introduction of a chiral linker between the two phosphorus atoms resulted in partial chirality control of the central and axial chiralities of the 2,2'-biphosphole framework, as three diastereoisomers a, b, and c are obtained among the six expected. In solution at room temperature a, b, and c diastereoisomers exist as an equilibrium mixture; the interconversion occurred by phosphorus-inversion inducing atropoinversion. Reaction of the equilibrium mixture of 2,2'-biphosphole with [MCl2(CH3CN)(2)] resulted in dynamic resolution leading to diastereo- and enantiopure Pd- and Pt-complexes. Palladium-catalyzed asymmetric allylic substitution can be achieved with the ligands 8 and 10 with high activities but still moderate enantioselectivities.