Stitching Ynones with Nitromethanes: Domino Synthesis of Functionally Enriched Benzofurans and Benzothiophenes

A convenient one-pot benzannulation of regioisomeric 2- or 3-substituted furan and thiophene ynones with a range of nitromethanes has been discovered to directly access densely and diversely functionalized benzofurans and benzothiophenes. In this protocol, the nitro group in nitromethanes functions as recursive carbanion activator to setup tandem Michael addition-6 pi-electrocyclization, and its eventual sacrificial elimination facilitates aromatization and overall benzannulation. This benzannulation was also explored with furan/thiophene based o-halo ynones wherein a Michael addition-SNAr process operates and nitromethanes leave their imprint to deliver nitro substituted benzo-furans and -thiophenes.

Automated summary

A convenient one-pot benzannulation method was discovered to directly access densely and diversely functionalized benzofurans and benzothiophenes. The nitro group in nitromethanes functions as a recursive carbanion activator to facilitate tandem Michael addition-6 pi-electrocyclization process for benzannulation. This method was also explored with furan/thiophene based o-halo ynones to deliver nitro substituted benzo-furans and -thiophenes through Michael addition-SNAr process.