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Ferrocene and 3,3′,4,4′‐tetramethyl‐1,1′‐diphosphaferrocene undergo efficient acylation by acyl trifluoroacetates (prepared in situ from carboxylic acids and trifluoroacetic anhydride) in the presence of an excess of trifluoromethanesulfonic acid or catalytic amounts (10% mol.) of its ytterbium or hafnium salts.
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Plażuk et al. (2004) studied this question.
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