Preparation and reaction of cyclopropyltriphenylphosphonium salt

Abstract Cyclopropyltriphenylphosphonium bromide ( 2a ) was conveniently prepared from 3-bromopropyltriphenylphosphonium bromide ( 1a ). The Wittig reaction of cyclopropyltriphenylphosphonium bromide ( 2a ) with carbonyl compounds gave alkylidenecyclopropanes ( 4 , 6 and 7 ). Successive treatment of 1a with two equivalents of base and carbonyl compounds gave alkylidenecyclopropanes ( 4 and 5 ) without isolation of intermediary 2a . 2-Methylcyclopropyltriphenylphosphonium bromide ( 2b ) was prepared and allowed to react with carbonyl compounds.