Efficient synthesis of benzo[c]cinnolines and azoarenes via dual C–N coupling of phthalhydrazide and trivalent halogen reagents

Abstract

Phthalhydrazide is proved to be an elegant N=N source to undergo tandem dual-C−N coupling/deprotection/oxidation with not only cyclic/linear diaryliodoniums but also rarely explored diarylbromoniums, giving benzo[c]cinnolines (up to 99% yield)...

Sequential annulation of bidentate diamines for modular access to N-fused/helical/spiro-carbazole scaffolds

“…11 For example, Wen 12 and Nachtsheim, 13 respectively, reported [4 + 1] annulative dual C–N coupling of anilines with cyclic diaryliodonium salts using Cu and Pd catalysis, while the reaction of ortho -substituted anilines has not been documented. Recently, our group reported the synthesis of benzo[ c ]cinnolines, 14 tribenzo[ b , d , f ]azepines, 15 and triphenylenes 16 using cyclic diaryliodonium salts. The retrosynthetic analysis of the N-fused Cz skeleton suggests that it could be accessed by intramolecular deaminative cyclization of N -aminoaryl carbazole which could be prepared from a cyclic diaryliodonium salt and a diamine (Scheme 1c).…”