(Cycloalkylidenemethyl)triphenylphosphonium Salts as Versatile Intermediate Reagents

Article abstract of DOI:10.1021/jo00248a008

The (cycloalkylidenemethyl)triphenylphosphonium salts 2b-d were synthesized in high yields by phenylselenylation of (cycloalkylmethylene)triphenylphosphoranes with benzeneselenenyl bromide to the triphenylphosphonium salts 1b-d and subsequent oxidative elimination of the phenylseleno moiety, while the synthesis of the (cyclopropylidenemethyl)triphenylphosphonium salt 2a was unsuccessful.Hydrolysis of 2b-d in aqueous THF and methanol containing sodium hydroxide was studied.The reactions of the (cyclohexylidenemethyl)phosphonium salt 2d and 1.1 equiv of butyllithium with aldehydes 9 gave alkenylcyclohexenes 10d-f in 56-81percent yields, whereas similar reactions using 1.5 equiv and 2 equiv of butyllithium produced allenes 11d-f as major products together with small amounts of 10d,e.Similar reactions of the (cyclopentylidenemethyl)phosphonium salt 2c and butyllithium with 9 gave alkenylcyclopentenes 10a-c in 56-80percent yields, regardless of the amount of butyllithium used.The formation mechanism of 10 and 11 was discussed.