Untersuchungen zur Bildung multifunktioneller 1,2‐Bis(tritylierter) Diphosphin‐Monoxide

Studies on the Formation of Multifunctional 1,2‐Bis(tritylated) Diphosphine Monoxides The products formed in the systems Ph₃CPH(:O) X /Ph₃CP( Y )Cl/NEt₃ with X = F, H, OH and Y = Cl, H, TMG (= N,N,N′,N′‐tetramethylguanidinyl) are discussed. In the case of the systems X =F/ Y =Cl, X =F/ Y =H, and X = Y =H the diphosphine monoxides 4 a , 5 a and 13 a were formed, while in the case of X =H/ Y =Cl, instead of the expected diphosphine monoxide 14 , a mixture of 13 a and of the POP compound 16 (molar ratio ca. 2 : 1) was observed. Treatment of 4 a with N,N,N′,N′‐tetramethylguanidine (= HTMG) led to the diphosphine monoxide, 7 a whereas its tautomer 7 b was formed, when Ph₃CP(TMG)Cl 6 reacted with Ph₃CPH(:O)F 1 . The conversion of one tautomer, 7 a or 7 b , into the other was not observed. On the other hand Cl₂P–PCPh₃(:O)F 8 a , formed as an intermediate in the reaction of 4 a with PCl₅, spontaneously rearranged to give Ph₃CPClF 9 and P(:O)Cl₃ as the final products. Surprisingly, oxidation of the σ³(P)‐atom in 4 a , 5 a and 13 a was impossible with H₂O₂ · (O:)C(NH₂)₂ as the oxidizing agent. The diphosphite 19 showed no rearrangement to the tautomeric diphosphine dioxide 18 , but oxidation to 20 was possible. All the products containing two asymmetrically substituted phosphorus atoms were obtained as diastereomeric mixtures of the meso and racemic form, as proved by ³¹P NMR spectroscopy.