Water-Soluble Phosphines. 17. Novel Water-Soluble Secondary and Tertiary Phosphines with Disulfonated 1,1‘-Biphenyl Backbones and Dibenzophosphole Moieties

Reaction of 2,2‘-difluoro-1,1‘-biphenyl with chlorosulfonic acid and subsequent hydrolysis followed by neutralization with potassium or sodium hydroxide affords disodium or dipotassium 5,5‘-disulfonato-2,2‘-difluoro-1,1‘-biphenyl (1a, 1b). On treatment of 1b with diphenyl- or phenylphosphine in the superbasic medium DMSO/KOH, phosphine ligand 2 or 3 with a disulfonated 1,1‘-biphenyl backbone or a dibenzophosphole moiety is formed. The structure of the oxide of 5-phenyldibenzophosphole 3, which crystallizes as 4·2.5H2O in the monoclinic space group P21/n with a = 13.799(3) Å, b = 19.246(4) Å, c = 17.764(4) Å, β = 105.63(3)°, and Z = 4, has been determined by X-ray analysis. Nucleophilic phosphination of 1a with NaPH2 in liquid ammonia yields the sodium phosphide 5a which on protonation gives the water-soluble 5H-dibenzophosphole 5. Reaction of 1b with PH3 in the superbasic medium DMSO/KOtBu affords 5b in addition to the oxidation product 6a. On oxidation of 5a or 5b with H2O2, the sodium or potassium salts of the sulfonated phosphinic acids 6a or 6b, respectively, are formed. Alkylation of the sodium dibenzophospholide 5a with 2,2‘-bis(chloromethyl)-1,1‘-biphenyl or 1,4-di-O-p-toluenesulfonyl-2,3-O-isopropylidene-d-threitol yields the chiral water-soluble bidentate phosphine ligands 8 and 9, respectively.