Ferrocene acylation

Berardi S, Conte V, Fiorani G et al (2008) Improvement of ferrocene acylation. Conventional vs. microwave heating for scandium-catalyzed reaction in alkylmethylimidazolium-based ionic hquids. J Organomet Chem 693 3015-3020... 

Table 4.15 Ferrocene acylation with carboxylic acid-TFAA mixtures promoted by alumina...

NOTE. This procedure prevents overloading of the chromatographic column during the separation of the reaction products. If the yield of crude reaction products exceeds 75 mg (the usual case), introduce one-half of the alumina-product mixture to the column. If the crude products, however, are obtained in quantities of less than 75 mg, add the entire alumina-product mixture to the top of the column. If only one-half of the alumina-crude ferrocene acylation product mixture is placed on the column, it is important to reweigh the tared vial to establish a reasonably accurate estimate of the overall yields obtained in the reaction. 

Some interesting results are observed in the study of bentonite-supported polytrifluoromethane-sulfosiloxane (B-PTMSS) as a catalyst in the acylation of ferrocene with different acyl chlorides [73] (ferrocene/acyl chloride ratio=0.5) (Scheme 3.13). 

In substituted ferrocenes, the substituent affects the reactivity of the substituted ring, the relative reactivity of the two rings, and hence the reactivity of the molecule as a whole. Thus the ease of oxidation of ferrocene is reduced by electron withdrawing, -I, substituents and, in acid media, the relative ease of oxidation is alkylferrocenes> ferrocene > acyl-ferrocene. A striking example is ferrocenyl-carboxaldehyde which resists... 

This experiment examines the effect of reaction time, temperature, and mole ratio of reactants on the synthetic yield of acetylferrocene by a Eriedel-Crafts acylation of ferrocene. A central composite experimental design is used to find the optimum conditions, but the experiment could be modified to use a factorial design. 

Ferrocene is acylated with a number of poly- and perfluonnated acid anhydrides [44],... 

The most notable chemistry of the biscylopen-tadienyls results from the aromaticity of the cyclopentadienyl rings. This is now far too extensively documented to be described in full but an outline of some of its manifestations is in Fig. 25.14. Ferrocene resists catalytic hydrogenation and does not undergo the typical reactions of conjugated dienes, such as the Diels-Alder reaction. Nor are direct nitration and halogenation possible because of oxidation to the ferricinium ion. However, Friedel-Crafts acylation as well as alkylation and metallation reactions, are readily effected. Indeed, electrophilic substitution of ferrocene occurs with such facility compared to, say, benzene (3 x 10 faster) that some explanation is called for. It has been suggested that. 

The cyclopentadienyl rings in ferrocene display some of the same chemical behavior as benzene. For example, ferrocene undergoes Friedel-Crafts mono and di acylation reactions, but at different rates. 

Friedel-Crafts acylation involves electrophilic attack by acyl cation (CHsCO ) on the ring, and the ring s electronic character should indicate its susceptibility to attack. Compare electrostatic potential maps of ferrocene and acetylferrocene. Which molecule contains the most electron-rich ring Which acylation reaction should be faster Does an acetyl substituent enhance or diminish ring reactivity What should be the major product when ferrocene is combined with one equivalent of acetic anhydride ... 

Singer and co-workers have investigated the acylation reactions of ferrocene in ionic liquids made from mixtures of [EMIMJI and aluminium(III) chloride (Scheme 6.1-5) [9, 10]. The ionic liquid acts both as solvent and as source of the Friedel-Crafts catalyst. In mildly acidic (X(A1C13) > 0.5 [EMIM]I/A1C13, the monoacetylated ferrocene was obtained as the major product. In strongly acidic [EMIM]I/AlCl3 X(A1C13) = 0.67 the diacylated ferrocene was the major product. Also, when R = alkyl, the diacetylated product was usually the major product, but for R = Ph, the monoacetylated product was favored. 

Formyl- und Acyl-ferrocene werden mit Lithiumalanat/Aluminiumchlorid in glatter Reaktion zu Alkyl-ferrocenen reduziert6 (auch Triphenyl-zinnhydrid in Gegen-wart von Acetylchlorid ist geeignet7). 

Ferrocene behaves in many respects like an aromatic electron-rich organic compound which is activated toward electrophilic reactions.In Friedel-Crafts type acylation of aromatic compounds with acyl halides, ferrocene is lO times more reactive than benzene and gives yields over 80%. However, ferrocene is different from benzene in respect to reactivity and yields in the Friedel-Crafts alkylation with alkyl halides or olefins. The yields of ferrocene alkylation are often very low. and the separations of the polysubstituted byproducts are tedious. 

H. Imai Kagaku Kyoto) 25, Chemistry of ferrocenes. IV 14 Japan. Acylated and halogenated ... 

Acyl cobalt complexes are reduced to their alkyl counterparts in good yields with Et3SiH/TFA (Eq. 248).183-310-425 Acyl ferrocene derivatives are reduced to the respective methylene compounds with Et3SiH/TFA (Eqs. 249180 and 250).179 Acylcyclopentadienylmanganese tricarbonyl is similarly reduced in good yield.351... 

Further developments of ferrocene based esters led to even faster acyl transfers to /3-CD (Trainor and Breslow, 1981 Breslow et al., 1983), the most spectacular rate accelerations, up to 6 million, being with the derivatives [17] and [18] in which an acrylate moiety is conformationally... 

Czamieki and Breslow (22) have studied the rate of acyl transfer from a substrate that is bound by the acyl part rather than by the leaving group. Having shown that ferrocene binds strongly to -cyclodextrin, Czamiecki and Breslow employed the p-nitrophenyl ester of ferrocinnamic acid in kinetic studies using DMSO-buffer mixtures. A rate acceleration of 51,000 times background was observed for acylation of /i-cyclodextrin. 

It has been reported [25] that PFR of ferrocene 96 of Scheme 29 produces the phenol acylated at the para position (97). The same authors have found that... 

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