A New Class of Planar-Chiral Ferrocenes:  Serendipitous Formation of 1,2-Ferrocenediylazaphosphinines

The reaction of 1-(α-aminoalkyl)-2-diphenylphosphinoferrocene (<BO>1</BO>) with glyoxals gave via an unusual heterocyclization 1,2-ferrocenediylazaphosphinines (<BO>3</BO>) as a new class of planar-chiral ferrocenes. The products were fully characterized by analytical and various spectroscopic techniques. In particular, a complete assignment of all protons and carbons was made by various NMR techniques. A substantial degree of π-electron delocalization extending over the fused heterocyclic ring can be evidenced by IR and UV/vis spectra and in the case of <BO>3a</BO> by X-ray crystallographic data. Employment of rac-<BO>3a </BO>as ligand for Cu-catalyzed cyclopropanation of styrene by ethyl diazoacetate revealed a complete diastereo-discrimination leading to the formation of trans-product in 100% yield.