Ferrocen-Derivate der Quadrat- und Propiolsäure. Synthesen und Reaktionen / Ferrocene Derivatives of Squaric Acid and Propiolic Acid. Syntheses and Reactions

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Abstract
Concepts for linking ferrocene derivatives with conjugated squarate and propiolate based spacer systems have been investigated. Coupling of 3,4-dichlorocyclobut-3-ene-1,2-dione (squaric acid dichloride) with cuproferrocene • dimethylsulfide resulted in 3-chloro-4-ferrocenylcyclobut-3-ene-1,2-dione (ferrocenylsemisquaric acid chloride) and 3,4-diferrocenylcyclobut-3-ene-1,2-dione. Ferrocenylsemisquaric acid chloride was further treated with ethynylferrocene and 4-ethynyl-4-(ferrocenylethynyl)tolan, respectively, to form the corresponding mixed squaric diketones, which required Zn/Pd mediated coupling conditions for sufficient conversion. The symmetrically substituted derivative of ferrocenylacetylene was prepared by the same method. Cupration and subsequent coupling of dilithioferrocene with one equivalent of iodopropiolic acid methyl ester yielded 1′-iodo- 1 -ferrocenylpropiolic acid methyl ester, and with two equivalents 1,16-bis(methoxycarbonylethynyl)biferrocene. Nucleophilic addition of secondary amines to ferrocenylpropiolic acid ethyl ester gave aminoacrylates as intermediates, which rapidly converted to ketoesters during workup. Only in the case of morpholine the corresponding adduct (ferrocenylmorpholino acrylate) could be isolated. 1,3-Diferrocenylprop-2-ene-1-one has been obtained in a Bénary reaction of lithioferrocene with 3-diethylaminoethyl acrylate in quantitative yield. In order to provide alternative syntheses of already known compounds the substitution behavior of different metallated ferrocene intermediates has also been evaluated by reaction with other acid halides (oxalyl chloride, thiophosgene, ethyl chloroformate). All new compounds, 3-chloro-4-ferrocenylcyclobut-3-ene-1,2-dione (1); 3,4-diferrocenylcyclobut-3-ene-1,2-dione (2); 3,4-diferrocenylethynylcyclobut-3-ene-1,2-dione (3); 3-ferrocenyl-4-ferrocenylethynylcyclobut-3-ene-1,2-dione (4); 3-ferrocenyl-4-ferrocenylethynylphenylethynylphenylethynylcyclobut-3-ene-1,2-dione (5); 3-(N-morpholino)-3-ferrocenylethyl acrylate (6); 3-ferrocenyl-3-ketoethyl propanoate (7); iodoferrocenylpropargylic acid methyl ester (8); 1,16-bis(methoxycarbonylethynyl)biferrocene (9) and trans-1,3-diferrocenylprop-2-ene-1-one [105 404-21-5], have been characterized by IR, MS and NMR and in several cases by UV/VIS and DSC.

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