Tripod-tripod coupling of triazides with triphosphanes. The synthesis, characterization, and stability in solution of new cage compounds: Chiral macrobicyclic triphosphazides

Several examples of a new type of cage compound, chiral macrobicyclic triph osphazides 15, have been prepared by tripod-tripod coupling of tris(2-azido benzyl)amines with 1,1,1-tris[(diphenylphosphino)methyl]ethane (triphos). T he structure determination of C-3 or pseudo-C-3-symmetric compounds 15 reve aled their propellerlike topology, which accounted for their chirality, the rare Z configuration of the three phosphazide units, and a new conformatio n of the triphos fragment. Compounds 15 decomposed in solution with a phosp hane arm-off mechanism, to give rise to complex mixtures instead of the exp ected tri-lambda(5)-phosphazenes. The stability of 15 in solution was enhan ced by the quaternization of the bridgehead nitrogen atom in the form of an N-oxide. Substituents either in the ortho position to the N termini of the phosphazide units or on the benzylic carbon atoms contributed to a decreas e in the stability of macrobicycles 15, and in some cases even prevented th eir preparation.