Electrophilic bis-fluorophosphonium dications: Lewis acid catalysts from diphosphines

摘要

Stepwise oxidation of 1,8-bis(diphenylphosphino)naphthalene and a series of (oligo)methylene-linked diphosphines with XeF2 followed by fluoride abstraction yields a family of compounds featuring phosphine, phosphonium and phosphorane moieties in close proximity. The bisphosphonium ions [(C10H6)(Ph2PF)2]²⁺ (>5) and [CH2(Ph2PF)2]²⁺ (>9a) exhibit remarkable Lewis acidity arising from the proximity of the phosphonium centers. The effectiveness of bisphosphonium dications (>5, >9a–e) is examined in a series of Lewis acid catalysed transformations.