Directed Electrophilic Cyclizations: Efficient Methodology for the Synthesis of Fused Polycyclic Aromatics

摘要: A versatile method for the synthesis of complex, fused polycyclic aromatic systems in high chemical yield is described. Construction achieved using a general two-step synthetic sequence. Pd-catalyzed Suzuki and Negishi type cross-coupling chemistries allow preparation nonfused skeletal ring yields consistently >80%. The critical ring-forming step, which generally proceeds very to quantitative yield, utilizes 4-alkoxyphenylethynyl groups induced by strong electrophiles such as trifluoroacetic acid iodonium tetrafluoroborate. reaction essence produces phenanthrene moieties are integrated into extended structures. Fused benzenoids well benzenoid/thiophene may be prepared utilizing this methodology. scope described cross-coupling/cyclization chemistry including mechanistic insights problematic side reactions