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].

Keywords: C−H activation; homogeneous catalysis; iron; phthalocyanines; spiro compounds.