HIGH-YIELD SYNTHESIS OF MONOSUBSTITUTED FERROCENES

The direct lithiation of ferrocene using an alkyllithium was widely explored and improved, but monolithioferrocene was never obtained fully devoid of 1,1'-dilithioferrocene. Pure (tri-n-butyl-stannyl)ferrocene was isolated in good yield from ferrocene (through the above lithiation). It can be stored and used (a) as an excellent precursor of pure monolithioferrocene, leading through reaction with many electrophiles to monosubstituted ferrocenes in nearly quantitative yields; (b) as a nucleophile in Stille cross-couplings with good results; (c) as a precursor of halogenoferrocenes through tin-halogen exchange.