Synthesis and resolution of the biaryl-like diphosphine (S)-Me2-CATPHOS, preparation of a derived rhodium precatalyst and applications in asymmetric hydrogenation

This protocol describes the synthesis of a representative example of the enantiopure biaryl-like CATPHOS class of diphosphines, ( S )-9,9′-dimethyl-9,9′,10,10′-tetrahydro-9,10,9′,10′-biethenobianthracene-11,11′-bis(diphenylphosphino)-12,12′-diyl (( S )-Me 2 -CATPHOS), and its derived cationic rhodium-based hydrogenation precatalyst. The C 2 -symmetric framework of Me 2 -CATPHOS is the result of a regioselective Diels-Alder cycloaddition between 1,4-bis(diphenylphosphinoyl)buta-1,3-diyne and 9-methylanthracene, such that the bulky methyl-substituted bridgehead carbon atoms are attached to C2 and C3 of the 1,3-butadiene tether. Enantiopure Me 2 -CATPHOS is obtained in an operationally straightforward three-step procedure and isolated in ∼50–60% overall yield and