Synthesis and Stereochemical Studies of Derivatives of 1,4-Dimethyl-2-phosphabicyclo[2.2.1]heptane

Abstract

1,4-Dimethyl-2-phenyl-2-phosphabicyclo2.2.1]heptane 2-oxide 1 was prepared by the reaction of 2,5-dimethyl-1,5-hexadiene with PhPCl₂-AlCl₃: stereo-assignments of the exo and endo isomers were established by ¹³C NMR spectroscopy (using lanthanide shift reagents) and by x-ray crystal structures. The isomers of 1 were separately reduced (phenylsilane) to give the phosphine derivative; in turn the phosphines were thermally equilibrated at 190°C to give a predominance (70%) of the exo-phenyl isomer.