From deprotometalation of ferrocenyl ketones to fused ferrocene structures

Although ferrocene ketones have been known since the early days of ferrocene chemistry, their behavior in deprotometalation has never been studied in detail. Here, we have optimized this reaction using lithium 2,2,6,6-tetramethylpiperidide in tetrahydrofuran containing ZnCl 2 · N , N , N' , N' -tetramethylethylenediamine as an in-situ trap. Numerous 2-iodoferrocene derivatives were obtained, while a change in regioselectivity was observed for certain aroyl- and heteroaroylferrocenes, in good agreement with our DFT calculations. The development of an enantioselective deprotometalation was also attempted using lithium di[( S )-1-phenylethyl]amide, affording the desired compounds in up to 60% enantiomeric excess ( ee ). A selection of iodinated derivatives was finally subjected to post-functionalizations, leading to original ferrocene-fused heterocycles, including an enantiopure tetracyclic derivative. A selection of compounds was studied in both electrochemical reduction and oxidation, and weak interactions such as halogen–halogen, halogen–oxygen and chalcogen–chalcogen bonds were identified in the solid state for some new derivatives.