Iron‐Catalyzed Oxidative C−C and N−N Coupling of Diarylamines and Synthesis of Spiroacridines

Abstract

We describe iron-catalyzed intermolecular oxidative coupling reactions of diarylamines to form substituted 2,2'-bis(arylamino)biaryl compounds, tetraarylhydrazines, and 5,6-dihydrobenzo[c]cinnolines with the same hexadecafluorinated iron-phthalocyanine catalyst. The mild formation of C-C or N-N bonds was controlled by the use of acidic or basic additives. In contrast to most iron-catalyzed dehydrogenative coupling reactions, ambient air could be used as the sole oxidant. Moreover, iron(III) chloride hexahydrate promoted a one-pot coupling and subsequent intramolecular dearomative coupling to give 10H-spiro[acridine-9,1'-cyclohexa-2',5'-dien-4'-ones].

Synthetic Applications of Oxidative Aromatic Coupling—From Biphenols to Nanographenes

“…In 2017, Knölker and co‐workers investigated the reactivity of diarylamines of type 27 towards iron(III)‐based catalysts: hexadecafluorinated iron‐phthalocyanine (FeF 16 Pc) and iron(III) chloride hexahydrate (Scheme ) . By using FeF 16 Pc as a catalyst, 2,2′‐di(arylamino)biaryls 28 , tetraarylhydrazines 29 , and 5,6‐dihydrobenzo[ c ]cinnolines 30 can be obtained in reasonable yields.…”

Iron‐Catalyzed Oxidative C−C and N−N Coupling of Diarylamines and Synthesis of Spiroacridines

“…A control experiment for the acid-catalyzed isomerization of the tetraarylhydrazine 6 a (20 mol % MsOH, air, CH 2 Cl 2 , RT) showed after 90 min the presence of mainly unreacted starting material. [21] Scheme 2. [20] Treatment of the diarylamines 1 with stoichiometric amounts of FeCl 3 ·6 H 2 O in dichloromethane at reflux under argon provided the 10H-spiro[acridine-9,1'-cyclohexa-2',5'dien-4'-ones] 7 (Table 5).…”

The 15th Frank Warren Organic Chemistry Conference

“…In a continuation of the theme of developing environmentally benign methodologies in his third visit to the conference, Prof. Dr. Hans‐Joachim Knölker walked us through his progress in regioselective iron(III)‐catalyzed intermolecular oxidative coupling of diaryl amines, as well the iron(III)‐catalyzed Wacker type oxidations . Prof. Dr. Hans‐Günther Schmalz gave an account of his group's work in the development of modular chiral P , P ‐ligands, for the enantioselective synthesis of structurally complex marine natural products .…”