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 fcX(2) (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)center dot 1/2C(6)H(6), and fc(NHCOOMe)(2)center dot MeOH are reported.