Novel Bis(1,3,2-diazaphospholidine) Ligands for Asymmetric Catalysis

A family
of modularly designed chiral bis­(1,3,2-diazaphospholidines) with N-aryl substituents (NP-PN) is reported. These compounds
have been prepared in two steps from readily available (R,R)-1,2-diaminocyclohexane and tetrachlorodiphosphines. Examples in
the set differ in the backbone and the aryl substituents, aiming at
their application in asymmetric catalysis. Thus, [Rh­(NBD)­(NP-PN)]­BF4 complexes lead to active catalysts in the hydrogenation of
methyl α-acetamidoacrylate, which provide enantioselectivities
up to 96% ee. In addition, NP-PN ligands also generate active catalysts
in the hydroformylation of vinyl acetate, leading to high regioselectivities
(iso:n ratio higher than 99:1) and
enantioselectivities up to 65% ee.