Alkynylphosphonium salts

These three synthetic methods can also be applied, generally, to a-alkynylphosphonium salts, with a C=C triple bond a to the phosphorus. New results have recently completed and enlarged the scope of each pathway. 

Alkynylphosphonium salts (115) are now conveniently accessible from the reaction of hexaphenylcarbodiphosphorane with aroyl chlorides. ... 

All varieties of alkynyliodonium salts readily react with triphenylphosphine resulting in the corresponding alkynylphosphonium salts in excellent yields. For cample, reaction of alkynyliodonium triflates with PhjP in cold dichloromethane gives alkynylphosphonium salts, 95, in nearly quantitative yields [75] [Eq. (50)J. 

Photochemical activation is not universally required for the conversion of alkynyliodo-nium salts into alkynylphosphonium compounds. For example, triphenylphosphine reacts with various alkynyl(phenyl)iodonium triflates in dichloromethane to give high yields of alkynylphosphonium triflates (equation 71)90. Since these reactions occur readily in the dark and are not inhibited by molecular oxygen or 2,6-di-terr-butyl-4-methylphenol, they are thought to proceed via the MC mechanism (equation 45)90. 

Certainly one of the most unusual nucleophiles to be treated with alkynyliodonium salts is the tetra-ter -butyltetraphosphacubane shown in equation 7791. However, despite its unique structure, this compound reacts with ethynyl(phenyl)- and l-propynyl(phenyl)-iodonium triflates in the now expected way to give good yields of alkynylphosphonium salts91. 

---