The First Examples of Enantiomerically Pure Diphosphane Dioxides-(RP,RP)- and (SP,SP)-1,2-Di-ter-butyl-1,2-diphenyldiphosphane 1,2-Dioxides, and (RP)- and (SP)-1-tert-Butyl-1,2,2-triphenyldiphosphane 1,2-Dioxides

Whereas oxidative dimerization of each of the lithiated reagents (RP)‐ and (SP)‐tert‐butylphenylphosphane oxides 1 Li and 2 Li by means of oxygen in THF at low temperature led cleanly to meso‐1,2‐di‐tert‐butyl‐1,2‐diphenyldiphosphane dioxide (3), the respective nucleophilic substitution reactions of 1 Li and 2 Li with the (RP)‐ and (SP)‐tert‐butylphenylphosphinic bromides (4 and 6) in THF under argon led to the corresponding (SP,SP)‐ and (RP,RP)‐12‐di‐tert‐butyl‐1,2‐diphenyldiphosphane dioxides (5 and 7) in good yields, together with the meso‐diphosphane dioxide 3. The structures of 3 and 5 were established by X‐ray crystallography. Similarly, the reaction of lithiated (RP)‐phosphane oxide 1 Li with diphenylphosphinic bromide (8) or of achiral lithiated diphenylphosphane oxide 10 Li with (RP)‐tert‐butylphenylphosphinic bromide (4) provided (SP)‐tert‐butyltriphenyldiphosphane dioxide (9). The first enantiomerically pure diphosphane dioxides have been prepared by nucleophilic substitution reactions of lithiated (Rp)‐ and (Sp)‐tert‐butylphenylphosphane oxides with (Rp)‐ and (Sp)‐terr‐butylphenylphosphinobromidates (below), of lithiated (Rp)‐phosphane oxide with diphenylphosphorobromidate, and of lithiated achiral diphenylphosphane oxide with (Rp)‐tert‐butylphenylphosphinobromidate. Formation of a small amount of meso diphosphane dioxide in the first example is shown not to involve electron transfer or degenerate halogen‐lithium exchange processes.