Fig. 2. Substrate scope for the synthesis of furan-fused cyclobutanones 2.

Reaction conditions: to a solution of Rh₂(OPiv)₄ (1.2 mg, 1.0 mol%), and 4 Å MS (100 mg) in EtOAc (1.0 mL), was added a solution of diazo compounds 1 (0.2 mmol) in EtOAc (1.0 mL) slowly over 10 min via a syringe under an argon atmosphere at 40 °C, and the reaction mixture was stirred for additional 1.0 h under these conditions. The yields are isolated yields. ^aThe reaction was carried out on a 5.0 mmol scale with 0.25 mol% of Rh₂(OPiv)₄ loading. ^bThe reaction was carried out in the presence of Rh₂(esp)₂ (1.0 mol%) in DCE at 80 °C.