TBHP‐Mediated Intermolecular Radical Coupling and Intramolecular Cyclization Cascade: Access to Furo[2,3‐b]quinoxalines and Their Photophysical Study

Abstract

A cascade one‐pot strategy to construct 31 examples of furo‐fused quinoxalines in up to 88% yields has been devised from readily accessible β‐ketothioamides and quinoxalin‐2‐ones in open flask at room temperature under TBHP mediated conditions. Mechanistic studies revealed that the overall reactivity relies on the seamless integration of intermolecular radical coupling and intramolecular cyclization via desulfhydration of C=S bond cleavage. Generation of H2S as the only by‐product makes this process highly attractive. Furthermore, the photophysical behavior of the furo‐fused quinoxalines has also been studied.

PIDA-promoted metal-free [3 + 2] heteroannulation of β-ketothioamides with 4-hydroxy coumarins: chemo-/regioselective access to furo[3,2-c]chromen-4-ones at room temperature

“…Recently, we devised a cascade metal-/catalyst-free strategy to construct furo-fused quinoxalines from β-ketothioamide and quinoxalin-2-ones at room temperature. 15 To this end, our continuing efforts to synthesize diverse heterocycles 16 prompted us to develop more innovative and sustainable methods for newer analogues. Herein, we report a convenient metal-free one-pot strategy to synthesize furo[3,2- c ]coumarins employing 4-hydroxy coumarin and β-ketothioamide at room temperature (Scheme 1d).…”