C₂-BIPNOR: An Easily Accessible Homologue of BIPNOR for Asymmetric Catalysis

Under mild conditions at −78 °C, the McMurry coupling of the (R)-2-formyl-1-phosphanorbornadiene 2 yields the enantiopure (RP, SC, SC, RP) diol 4, dubbed C2-BIPNOR. In boiling THF, the same reaction leads to the trans-alkene 6. C2-BIPNOR is easier to prepare and to handle than BIPNOR while benefiting from the same configurational stability at phosphorus. It appears to have a wider range of catalytic applications than BIPNOR and, in one case (asymmetric Heck reaction), to be competitive with the best ligands proposed in the literature.