949172-68-3Relevant articles and documents
First modular synthesis of dissymmetric biaryldiphosphine ligands allowing tunable steric and electronic effects
Leroux, Frederic R.,Mettler, Hanspeter
, p. 323 - 336 (2008/02/07)
The first modular synthesis of a family of C1-symmetric diphosphine ligands is presented. Their synthesis is based on unprecedented highly regioselective halogen/metal interconversions on a common polybrominated biaryl precursor. This methodology allows the functionalization of the ortho- and ortho'-positions of the biaryl core. Diphosphine ligands carrying only one substituent at the 6-position and the two phosphine substituents at the 2- and 2′-position become easily accessible. The two phosphine substituents may be identical (as in compounds 2 and 3) or different (as in compounds 1 and 4). All diphosphines were prepared on gram scale, and the enantiopure ligands were obtained by chromatography of the racemate on a chiral HPLC column. The asymmetric hydrogenation of β-keto esters, acetamidocinnamates and dimethyl itaconate revealed good to excellent asymmetric inductions of up to 99 % ee, and are often close to those of the well-known C2-symmetric MeO-BIPHEP.
