Phosphinodefluorination of polyfluorobenzenes by silylphosphines Ph(R)PSiMe3 (R = Me, Ph): Further experimental and computational evidences for the concerted ANDN mechanism of aromatic nucleophilic substitution

Abstract Trimethylsilylphosphines PhRPSiMe 3 (1 R = Me, 2 R = Ph) have been shown to phosphinodefluorinate 1,2,3- ( 3 ), 1,3,5- ( 4 ) and 1,2,4-trifluorobenzene ( 5 ) in benzene solution or without solvent at 150–200 °C to form the respective (difluorophenyl)methylphenyl- and -diphenylphosphines in high NMR yields under harder conditions compared to the previously reported reactions of Me 2 PSiMe 3 with the same substrates. Hexafluorobenzene ( 6 ), pentafluorobenzene ( 7 ) (at 150 °C), octafluorotoluene ( 8 ) and pentafluoropyridine ( 9 ) (at 20 °C) react with phosphine 2 without a solvent almost quantitatively under fluorine 1,4-disubstitution (for 6 ) or monosubstitution (for 7–9 ) by the Ph 2 P group to give the corresponding (polyfluoroaryl)diphenylphosphines in 50–60% (for 6–8 ) and 95% (for 9 ) isolated yields. The regio and substrate selectivities exhibited by 3–5 in the reactions of the single substrates and in competitive reactions of 3 vs. 4 with 1 or 2 and 4 vs. 5 with 2 indicate relative fluorine substituent rate factors f o -F  >  f m -F consistent with the concerted A N D N mechanism which is supported by high level quantum chemical DFT-studies for the reactions of the substrates 3 and 4 with 1 , 2 and 10 as well as for 6 with 2 .