Silver-Catalyzed Ring Expansion of Activated N-Heteroarenes via 1,4-Dearomative Addition of Diazomethylphosphonates

Phosphorus-containing N-heterocycles are important molecular motifs due to their unique structural features and biological activities. In this study, we developed a silver-catalyzed reaction for the construction of phosphorus-containing azepine derivatives via a domino-type dearomatization procedure, followed by ring expansion. In addition, diazomethylphosphonates were employed for the first time as nucleophiles in the 1,4-dearomative addition of activated N-heteroarenes, furnishing cyclopropane-fused piperidine intermediates that were readily restructured into their corresponding azepine derivatives. The reactivities of the diazomethylphosphonates in the developed dearomatization strategy were found to be superior to those of other diazo compounds, thereby resulting in the generation of the desired seven-membered N-heterocycles within a very short reaction time.