Dearomative [3 + 2] cycloaddition reaction of nitrobenzothiophenes with nonstabilized azomethine ylides.

A highly diastereoselective dearomative [3 + 2] 1,3-dipolar cycloaddition reaction of nitrobenzothiophenes with an -generated nonstabilized azomethine ylides has been developed. The transformation provides a series of functionalized fused tricyclic benzo[4,5]thieno[2,3-]pyrroles in good yields (up to 92%) under mild reaction conditions. In addition, a gram-scale experiment and the synthetic transformation of the cycloadduct further highlighted the synthetic utility. The relative configurations of the typical products were clearly confirmed by X-ray crystallography.