Insertion of phosphinidene complexes into the P–H bond of secondary phosphine oxides: a new version of the phospha-Wittig synthesis of PC double bonds
Terminalphosphinidenecomplexes [RP-W(CO)5], as generated at 60 °C in the presence of copper chloride from the appropriate 7-phosphanorbornadiene complexes, react with secondary phosphine oxides Ar2P(O)H to give the insertion products into the P–H bonds. After metalation with NaH, these products react with aldehydes to give the corresponding phosphaalkenes which are trapped by dimethylbutadiene.
Transient terminal phosphinidene complexes [RP-W(CO)(5)] dimerize in the presence of copper chloride, and the dimers react in situ with triphenylphosphine-borane to give the disecondary diphosphine complexes [RPH-PHR][W(CO)(5)](2). When R = CH2CH2Cl, a cyclization takes place to give the diphosphirane complex. A 1,2-diphospholane is obtained for R = Ph by further reaction with 1,3-dibromopropane in the presence of aqueous K2CO3.