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

The reaction of 1-(α-aminoalkyl)-2-diphenylphosphinoferrocene (1) with glyoxals gave via an unusual heterocyclization 1,2-ferrocenediylazaphosphinines
(3) 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 3a by X-ray crystallographic data.
Employment of rac-3a 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.