Cyclic aromatic analogues of the hendrickson reagent; NMR studies and electrophilic properties

Two novel cyclic aromatic analogues of the Hendrickson POP reagent, 1,1,3,3-tetraphenyl-1,3-dihydro-2,1,3-benzoxadiphosphole-1,3-diium bis(trifluoromethanesulfinate) and bis(trifluoromethanesulfonate), have been readily prepared by the treatment of 1,2-bis(diphenylphosphino)benzene or 1,2-bis(diphenylphosphoryl)benzene, respectively, with trifluoromethanesulfonic anhydride in dichloromethane. ³¹P and ¹⁹F NMR studies indicated that while the latter complex is formed as the sole product, the former species was shown to be the predominant component in equilibrium with 1-(diphenylphosphino)-2-[diphenyl(trifluoromethylsulfonyloxy)phosphonio]benzene trifluoromethanesulfinate and 1,2-bis[diphenyl(trifluoromethylsulfonyloxy) phosphonio]benzene bis(trifluoromethanesulfinate). The dehydrating POP systems were exploited in the conversion of aldoximes into nitriles. The dehydration occurred rapidly at room temperature and produced high yields with a variety of alkyl- and arylaldoximes, tolerating a wide range of substrates and functional groups.