Silver‐Catalyzed One‐Pot Access to Diastereoselective Benzo[5,6]oxepino[2,3‐c]pyrroles via Formal (5+2)‐Annulation of Donor‐/Acceptor‐Type Aryl Vinyl Diazosuccinimide with Ketones

• Published in: Asian journal of organic chemistry 2022-04, Vol.11 (4), p.n/a
• Main Authors: Laha, Debasish, Meher, Kajal B., Bankar, Onkar S., Bhat, Ramakrishna G.
• Format: Article
• Language: English
• Subjects: Annulation; Diastereoselective; Dihydrobenzoxepines; Silver catalysis; Vinyl diazosuccinimide
• ISSN: 2193-5807; 2193-5815
• DOI: 10.1002/ajoc.202200062

A silver triflimide catalyzed one‐pot protocol for the diastereoselective synthesis of dihydrobenzoxepines has been developed. Silver triflimide was found to be an efficient catalyst for the formal (5+2)‐cycloaddition to access dihydrobenzoxepines as a single diastereomer using vinyl diazosuccinimides as 5‐C‐synthons and ketones. An unmet challenge of utilizing the donor‐/acceptor‐type vinyl diazosuccinimides as 5‐C‐synthons under silver‐catalysis is presented. This protocol was found to be highly regio‐, chemo‐ and diastereoselective, and works well with aliphatic as well as aromatic methyl ketones bearing electron deactivating as well as donating groups to afford dihydrobenzo[5,6]oxepino[2,3‐c]pyrroles. The control experiments and time‐dependent NMR studies revealed the plausible mechanism of this transformation. The protocol also proved to be scalable on the gram‐scale synthesis. Dihydrobenzoxepine scaffold is one of the important and useful oxygenated heterocycles. A one‐pot diastereoselective synthesis of dihydrobenzoxepines has been achieved via a formal (5+2)‐cycloaddition of vinyl diazosuccinimides and ketones under silver catalysis. Aliphatic as well as aromatic methyl ketones afforded the corresponding dihydrobenzoxepines with high regio‐ and chemo‐selectivity. Further insight into the reaction mechanism has been established using control experiments and time‐dependent NMR studies.