Synthesis, molecular structure, and properties of in-phosphaphanes with substituted basal aromatic rings

Abstract

A series of nitro-substituted phosphine-containing cyclophanes (2-4) was prepared by base-promoted condensation of various nitrated derivatives of 1,3,5-tris(bromomethyl)benzene with tris(2-mercaptophenyl)phosphine under conditions of high dilution. The mononitro cyclophane 2 was reduced with TiCl 3 in THF-EtOH to give the corresponding amino derivative 5. The 13 C NMR spectra of these compounds exhibit «through-space» spin-spin coupling between the phosphorus and the substituted banal aromatic ring, and in their 31 P NMR spectra the phosphorus resonances are anomalously far downfield.The X-ray crystal structures of cyclophanes 4 and 5 reveal a pronouced inward pyramidalization of the phosphines such that the phosphorous atoms are 2.98 and 2.92 A, respectively, from the centers of the basal rings.These cyclophanes are rigid, molecular propellers, and compound 2 was chromatographically resolved on a chiral HPLC column.The circular dichroism spectra of the pure enantiomers showed a very high molecular ellipticity at 332nm of 120 000 deg;cm 2 .dmol -1