Enantioselective Synthesis of Planar Chiral Ferrocene Triflones

A multi‐gram scale synthesis of ferrocenetriflone was optimised from ferrocenesulfonyl fluoride and Me₃SiCF₃ (Ruppert reagent). Enantioselective deprotolithiations were then carried out using alkyllithiums in the presence of catalytic (+)‐sparteine to afford 2‐substituted ferrocene triflones with ee up to 84%. The use of chiral lithium amides in the presence of in situ traps was also optimised and was found to outperform alkyllithium∙chiral diamine chelates for the first time in the ferrocene series, with ee up to 93%. Crystallisation of derivatives afforded enantiopure compounds that were engaged in deprotolithiation‐electrophilic trapping sequences, a halogen ‘dance' reaction and transition metal promoted coupling to afford a wide range of variously polysubstituted ferrocene triflones.