Large-Scale Preparation of 1,1′-Ferrocenedicarboxylic Acid, a Key Compound for the Synthesis of 1,1′-Disubstituted Ferrocene Derivatives

Efficient and simple methods for the large-scale preparation of 1,1′-ferrocenedicarboxylic acid, fc­(COOH)2, involving the sodium salts of cyclopentadienecarboxylic methyl and ethyl esters, Na­(C5H4COOR) (R = Me, Et), are presented. With fc­(COOH)2 at hand, the syntheses of various 1,1′-disubstituted compounds of the type fcX2 (X = CH2OH, COCl, CON3, NCO, NHCOOMe, NHBoc, NH2) were optimized and scaled up. The X-ray crystal structures of fc­(COOEt)2, fc­(NCO)2·1/2C6H6, and fc­(NHCOOMe)2·MeOH are reported.