Yb(OTf)₃‑Mediated Access to Furans from β‑Ketothioamides via Eschenmoser Sulfide Contraction Reaction

A mild and straightforward synthetic protocol for construction of a furan skeleton promoted by Yb­(OTf)₃ from β-ketothioamides and arylglyoxals has been developed at room temperature. Importantly, this protocol involves a tandem sequence that includes aldol condensation, N-cyclization, ring opening, O-cyclization, S-cyclization, and Eschenmoser sulfide contraction.