New Synthesis of Ferrocene Monocarboxylic Acid and Systematic Studies on the Preparation of Related Key-Intermediates

Abstract

An improved technique for the preparation of ferrocenecarboxaldehyde and two new methods for the synthesis of ferrocenemonocarboxylic acid from the aldehyde or from acetyl ferrocene are described. Using the aldehyde or the monocarboxylic acid as starting materials, some important ferrocene key intermediates were prepared: mono-chlorocarbonyl ferrocene, alkali metal and ammonium ferrocenoates, ferrocene carboxyaldehyde diethylacetal, ferrocenecarboxamide, et . . ., as well as a new ferrocene derivative: piperazinium diferrocenoate.

Reaction of ferrocenecarboxylic acid with N,N′-disubstituted carbodiimides: synthesis, spectroscopic and X-ray crystallographic analysis of N,N′-disubstituted N-ferrocenoylureas and identification of a one-pot coupling reagent for the formation of ferrocenecarboxamides in a non-aqueous solvent

“…The question if the product of the reaction between DCC and 1 is N ,N 0 -dicyclohexyl-O-ferrocenoylisourea 13 according to [5] or 2 according to [2][3][4]6] as well as the question if the product between carbodiimides and 1 in general is an N ,N 0 -disubstituted O-ferrocenoylisourea or an N ,N 0 -disubstituted N -ferrocenoylurea was investigated by 1 H NMR, as well as 13 C NMR spectroscopy, MS and in the case of the reaction between DCC, DIC or 10 and 1 by a single crystal structure analysis of the products.…”

“…In the interpretation of the 1 H NMR spectrum of compound 2 [4] the multiplet between 2.20 and 1.00 ppm was erroneously assigned to all 22 instead of 20 protons of the cyclohexyl rings. Furthermore, one of the other two protons of the cyclohexyl rings between 3.5 and 3.6 ppm was erroneously identified as the NH proton, while the second at 4.2 ppm and the NH proton failed to be noticed at all.…”

“…Furthermore, in the region between 2800 and 1800 cm À1 no significant absorption is detectable. In an earlier IR spectroscopic investigation [4] a band at 2100 cm À1 was registered and identified as NH-CO-N-CO stretching band. In this region of wave numbers, however, for 2 no band is detectable and the band discussed in [4] is probably caused by DCC impurities.…”

“…None of the other carbodiimides, especially DCC and DIC, usually employed in non-aqueous solution, was successful in this case. It is not necessary to prepare the chlorocarbonylferrocene [4] or another activated ferrocene derivative [10] in a separate step. We are currently using 17 as a synthetic building block for the modification of silica nanoparticles [15].…”

“…Ferrocenecarboxylic acid 1 reacts in a different way with DCC, and N ,N 0 -dicyclohexyl-N -ferrocenoylurea 2 (structure B) is the main product, as already discussed in the literature [2][3][4][5][6], but either no spectroscopic investigation was made [2,3], the 1 H NMR and the IR spectra were incorrectly interpreted [4], or the substance was erroneously identified as N ,N 0 -dicyclohexyl-O-ferrocenoylisourea [5]. One report [6] about the formation of 2 from DCC and 1 in the presence of 2-(6-hydroxyhexyloxy)-3-methoxy-6,7,10,11-tetrahexyloxytriphenylene includes a crystal structure and a 1 H NMR spectrum, however without interpretation.…”