Aryl Grignard Reagents in Chemodivergent N‐ and C‐Arylations: Concise Access to Two Families of Tetracyclic Fused Carbazoles from 6‐Nitroquinolines

Abstract

AbstractThe reaction between aryl Grignard compounds and 5‐methoxy‐6‐nitroquinoline derivatives in THF was found to proceed in a chemodivergent mode that depended on the functional groups present in the heterocyclic ring. Thus, the reactions that started from carbostyril derivatives afforded 6‐(arylamino)carbostyrils as the major products, whereas those that started with 2‐alkoxyquinolines gave exclusively 5‐arylquinolines. Both types of products were transformed into tetracyclic fused linear or angular carbazole systems by using palladium‐promoted oxidative coupling or Cadogan reactions, respectively. In the course of this work, an unprecedented oxidative demethylation by palladium acetate of 1,4‐dimethoxybenzene systems to the corresponding quinones was discovered.