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We report the extension of an easy one-step synthesis of amino gembisphosphonates through the reaction of amides and lactams with trialkylphosphites.

The optimization of the one-step diphosphorylation reaction is reported. The synthesis of new α-aminobisphosphonates with four and six-membered rings and acyclic species with several substituents on the nitrogen and on the carbon atom bearing the two phosphorus atoms is described.

For geminally diphosphorylated linear nitroxide radicals, a marked line width alternation (LWA) can be observed. The LWA appears irrespectively whether the investigated radicals R''N(O . )C(P(O)(OEt) 2 ) 2 R' contain any chiral group or not. If R"=tertio-butyl and R'=H, the small β-hydrogen coupling indicates a completely blocked rotation around the N-C σ-bond and the LWA can be assigned to a chemical exchange between conformations in which the phosphoryl groups have a symmetric and a non-symmetric geometry. The conformational change is accompanied with the deformation of the CP 2 bonding angle and the rate of exchange is slowed down in pentane for which the solvent molecules can be trapped by the chelating phosphoryl groups. If R"=benzyl, both the proton hyperfine lines of the CH 2 group and the phosphorus lines of the CP 2 group produce a LWA ; two coalescences can be observed. In the case of a chiral R" group (R"=secondary butyl, R'=methyl) a tentative four-site model can explain the highly complex LWA.

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ESR spectra of cis- and trans-β-diphosphorylated pyrrolidine-N-oxyl radicals, c-1 and t-1, were studied in liquid and frozen solution. The expected 1:2:1 triplet (a P (2)) of the 1:1:1 triplet (a N) was observed for t-1; however, for c-1, the inner lines of the 1:2:1 triplet showed a dramatic broadening characteristic of chemical exchange between two equivalent conformations. Owing to the large difference in the hyperfine splitting constants (hfsc) of the exchanging phosphorus (Δa P ≈ 21 G), the coalescence temperature was unusually high (193 K, in n-pentane), and the potential barrier for ring interconversion (10.5 kJ mol-1) was easily obtained from the temperature dependence of the exchange rate. This value was in very good agreement with the value obtained for an empirical pseudorotational potential (11 kJ mol-1) that was adjusted to fit the temperature dependence of the phosphorus hfsc. For c-1, molecular mechanics calculations gave similar characteristics for the pseudorotational potential and indicated the existence of two identical minima with distorted geometries lying between 3T4 and 3E or 4T3 and E3. For t-1, only the 3T4 conformer was found to be significantly populated. Frozen solution spectra showed that the phosphorus hfsc anisotropy is higher when the C−P bond is pseudoaxial; this result can be explained by a geometry-dependent delocalization of the unpaired electron into the phosphorus 3p orbitals.