New conformational flexible phosphane and phosphane oxide macrobicycles

The synthesis of two large diastereomeric phosphane oxide macrobicycles 3 and 4 succeeded in comparatively good yield by a tripod-coupling strategy using the tripodal components 1 and 2 as building blocks. 1H, 13C and 31P NMR spectra of the two cage compounds are in accordance with a time-averaged D3h symmetry each, which in the case of 3 can be attributed to a fast interconversion of two degenerate in,out-structures. Kinetic measurements of the reduction of both diastereomeric macrobicycles, and the results of an inversion experiment also support the assumption that the phosphane and phosphane oxide cage molecules described herein are conformational flexible and undergo fast homeomorphic isomerisation. The bisiminophosphorane derivative 8 was prepared and assigned as an out,out-isomer. An alternative tripod-capping reaction between bisphenol 10 and capping reagent 2 did not result in the formation of macrobicyclic products. Instead, three complex structures 11, 12 and 13 with macrocyclic sub-units could be isolated.