Pd-catalysed C–H bond functionalisation route to 1,2-dihydroferroceno[c]isoquinoline and its annellated derivatives and the reactivity of these compounds

Abstract

C–H bond functionalisation has developed into a powerful synthetic methodology that is applicable to a wide array of substrates, including organometallic compounds. In this study, racemic, planar-chiral 1,2-dihydroferroceno[c]isoquinoline and analogous helical compounds with one or two additional ortho-fused benzene rings were synthesised by palladium-catalysed C–H bond activation/cyclisation of N-[(bromoaryl)methyl]-N-(methylsulfonyl)aminoferrocenes. These starting materials are readily accessible from FcNHSO₂Me (Fc = ferrocenyl) and appropriate vicinal bromo-(bromomethyl)arenes. The racemic products were successfully enantioseparated using chiral chromatography and the representative compound, 1,2-dihydro-2-(methylsulfonyl)ferroceno[c]isoquinoline, was converted to the unstable ferroceno[c]isoquinoline and further used to prepare a heterobimetallic, Fe/Ru bis-metallocene complex via a reaction with [(η⁵-C₅Me₅)Ru(MeCN)₃][PF₆]. All compounds were characterised by spectroscopic methods (NMR, FTIR, and UV-vis) and mass spectrometry and, in most cases, the structures were determined by single-crystal X-ray diffraction analysis. In addition, the representative compounds were examined by cyclic voltammetry, and the results were rationalised with the aid of DFT calculations.