Reactivity of Planar-Chiral alpha-Ferrocenyl Carbocations towards Electron-Rich Aromatics

The reaction of the enantiopure, planar-chiral alpha-ferrocenyl carbocation (S-p)-2-(P(=S)Ph-2)FcCH(2)(+) (Fc = Fe(eta(5)-C5H5)(eta(5)-C5H3)) towards electron-rich arenes C6H5E (E = NH2, NMe2, NiPr2, NPh2, PPh2, P(=S)Ph-2, OH, SH, SMe) regarding either a nucleophilic attack of the group E or an electrophilic aromatic substitution reaction of the arene at the CH2+ unit is reported. It was found that the amino, oxo or thio functionalities gave the respective ferrocenes in various product distributions, while the P-based species didn't. Appropriate thiophosphine derivatives could be reduced to their P-III species that were applied as supporting ligands in atropselective C,C cross-coupling reactions for the synthesis of sterically hindered biaryls, where sandwich compound (S-p)-1-(PPh2)-2-(o-NMe2-C6H4)CH2-Fc gave an ee of 69 % (1 mol-% [Pd]), which is up to date the highest observed value for planar-chiral ferrocenes. The absolute configuration of the chiral ferrocenes was confirmed by single-crystal X-ray diffraction analysis. For seleno phosphane 1-(P(=Se)Ph-2)-2-(CH2OH)-Fc a unique Se single-atom transfer occurred within its reaction with Sanger's reagent. The presence of two chemically different Se atoms in 1-(P(=Se)Ph-2)-2-(((2,4-(NO2)(2)-C6H3)Se)CH2)-Fc was confirmed by Se-77{H-1} NMR spectroscopy and single-crystal X-ray diffraction analysis, respectively.