Diphosphine oxides resolution

Synthesis of chiral atropisomeric diphosphine type ligands is a current challenge in chemical research because their late transition metal complexes usually provide high enantioselectivity in homogenous catalytic reactions. [28] In practical point of view, preparation and optical resolution of racemic diphosphine oxides followed by the reduction of the separated enantiomers are usually more advantageous than an expensive enantioselective synthesis of one diphosphine enantiomer. [29]... 

Dziuba K, Flis A, Szmigielska A, Pietrusiewicz KM (2010) Efficient oxidative resolution of a F-stereogenic triarylphosphine and asymmetric synthesis of a F-stereogenic atropoisomeric biphenyl diphosphine dioxide. Tetrahedron Asymmetry 21 1401-1405... 

Resolution of phosphine oxides involves protonation of the weakly basic phosphoryl group by the chiral auxiliary. This method showed limited success for simple monophosphine oxides (entries 1, 2 and 10) but is better suited to resolve compounds bearing carboxylic acid groups (entries 11 and 12) or diphosphine oxides (entries 16-20). It is still sporadically used nowadays, as for the compounds of entries 19 and 20. 

J. Org. Chem., 62, 5452. [(Rp)-PHANEPHOS used in this procedure is actually the diphosphine derivative of dibromo-Pc after resolution of the diphosphine oxide with dibenzoyl-D-tartaric acid]. 

A new diphosphine ligand, Norphos , catalyses the reduction of Z-a-(acetyl-amino)cinnamic acids to the expected dihydrocinnamic acids with optical yields of ca. 96%. ° The ligand is prepared from trans-vinylidenebis(diphenylphosphine oxide) by a Diels-Alder reaction with cyclopentadiene, classical resolution using (L)-(-)-dibenzoyltartaric acid, and finally reduction. The same substrates can also be reduced in ca. 80% optical yields using diphosphine ligands derived from enantiomerically pure menthoP or mandelic acid. ... 

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