1,2-Disubstituted Planar Chiral Ferrocene Derivatives from Sulfonamide-Directed ortho-Lithiation: Synthesis, Absolute Configuration, and Chiroptical Properties

A straightforward approach to the synthesis of a series of 1,2-disubstituted planar chiral ferrocenes was achieved using the ortho-directed lithiation of chiral ferrocenesulfonamides followed by a reaction with electrophilic reactants. The planar 1,2-functionalized ferrocenesulfonamides were obtained in good yields, and the individual diastereoisomers could be isolated in the pure form. The relative configurations of the chemical groups in positions 1 and 2, which are relevant for the planar chirality, were derived from NMR experiments, and the absolute configuration was determined by X-ray crystallography. Experimental ECD and VCD spectra were recorded, assigned, and interpreted by means of state-of-the-art quantum chemical computations, which allow for an unbiased analysis of the different structural factors that tune the overall spectroscopic features.