Details

Autor(en) / Beteiligte

• Korb, Marcus
• Mahrholdt, Julia
• Liu, Xianming
• Lang, Heinrich

Titel

Reactivity of Planar‐Chiral α‐Ferrocenyl Carbocations towards Electron‐Rich Aromatics

Ist Teil von

• European journal of inorganic chemistry, 2019-02, Vol.2019 (7), p.973-987

Ort / Verlag

Weinheim: Wiley Subscription Services, Inc

Erscheinungsjahr

2019

Link zum Volltext

Quelle

Wiley Online Library All Journals

Beschreibungen/Notizen

• The reaction of the enantiopure, planar‐chiral α‐ferrocenyl carbocation (Sp)‐2‐(P(=S)Ph2)FcCH2+ (Fc = Fe(η5‐C5H5)(η5‐C5H3)) towards electron‐rich arenes C6H5E (E = NH2, NMe2, NiPr2, NPh2, PPh2, P(=S)Ph2, 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 PIII species that were applied as supporting ligands in atropselective C,C cross‐coupling reactions for the synthesis of sterically hindered biaryls, where sandwich compound (Sp)‐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)Ph2)‐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)Ph2)‐2‐(((2,4‐(NO2)2‐C6H3)Se)CH2)‐Fc was confirmed by 77Se{1H} NMR spectroscopy and single‐crystal X‐ray diffraction analysis, respectively. The conversion of enantiopure ferrocenylmethanol 1a into its α‐carbocation and subsequent reaction with electron‐rich arenes is investigated. They preferably undergo SEAr or SN reactions depending on E. Reduction into phosphines and usage as ligands in C,C cross‐coupling catalysis gave biaryls with up to 69 % ee. Electron‐poor substrates enabled a transfer of the P=X chalcogene (X = S, Se) towards the cation.