A General Method to Prepare Monodentate Phosphane Ligands with Mixed Substituents

Treatment of (2,2'-biphenylylene)phosphorchloridite ester [(C12H8O2)PCl] (1) with C2F5Li yields (C12H8O2)PC2F5 2; treatment of 1 with Grignard reagents yields compounds of the type (C12H8O2)PR (R = Pr-i, 5; Et 6). In both cases, the 1,3-dioxepine ring formed when 2,2'-biphenol reacts with PCl3 to form 1 serves as a protecting group at the phosphorus atom; the ring allows the stepwise introduction of one substituent and prevents undesirable product mixtures associated with multiple substitutions at the phosphorus. Additional treatment of compounds 2, 5, and 6 with Grignard, alkyl, or aryllithium reagents results in the formation of unsymmetrically substituted phosphanes. The use of (2,2'-biphenylylene)phosphorchloridite ester as a starting material for the preparation of electroneutral phosphanes of the type (R-f)PR2 and electron-poor phosphanes of the type (R-f)(2)PR is described. (C) 2010 Wiley Periodicals, Inc. Heteroatom Chem 20:393-397, 2009; Published online in Wiley Inter-Science (www.interscience.wiley.com). DOI 10.1002/hc.20563