Abstract
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.
Key words
1,2-bis(diphenylphosphino)benzene - 1,2-bis(diphenylphosphoryl)benzene - trifluoromethanesulfonic anhydride - Hendrickson
reagent - dehydration - aldoximes - nitriles
