A new approach to β-functional phospholes. Application to the synthesis of a β-CH2CH2-bridged diphosphole disulphide

Protection of both the dienic system and the lone pair of phosphorus of 1-phenyl-3,4-dimethylphosphole by complexation with iron carbonyl groups allow the regiospecific deprotonation of one β-methyl substituent by lithium diisopropylamide (LDA). The resulting anion exhibits versatile reactivity towards various electrophiles and can even undergo oxidative coupling with CuCl2, thus providing an entry into the unprecedented β–β′-bridged biphosphole system. Finally, the protecting iron carbonyl moieties can be cleanly removed in a two-step procedure involving reaction with sulphur and cerium ammonium nitrate (CAN).