Stereoselective construction of azepine-containing bridged scaffolds via organocatalytic bicyclization of yne-allenone esters with nitrones

Meng-Fan Li,¹ Shao-Qing Shi,¹ Ting Xu,¹ Qian Zhang, Wen-Juan Hao, Shu-Liang Wang,* Jianyi Wang,* Shu-Jiang Tu, Bo Jiang*

A new organocatalytic double annulation cascade involving scission/recombination of N-O bonds of nitrones is reported for the first time, and used to produce a range of hitherto unprecedented tricyclic bridged-fused benzo[d]azepines bearing three stereogenic centers with moderate to good yields and complete diastereoselectivity. A quinine-catalyzed reaction of yne-allenone esters with nitrones worked well and provided a convergent and regioselective pathway to access these three-dimensional scaffolds from the planar conjugated system. Density functional theory (DFT) calculations have been applied to understand the key process for forming diradical intermediates.

Chin. Chem. Lett. 2023, 34, 107751; DOI: 10.1016/j.cclet.2022.107751