[2+2] Photocycloaddition reaction of 5-arylfuran-2,3-diones to trimethylsilyloxyethylenes

The photocycloaddition reaction of 5-phenylfuran-2,3-dione (la) to 2-trimethylsilyloxybutadiene proceeded in a [2s+2s] manner with high regio- and stereo-selectivities to give a 2-oxabicyclo[3.2.0]heptane-3,4-dione 2 with 7-endo-OTMS-7-exo-vinyl stereochemistry. 5-Arylfuran-2,3-diones (1a-e) on similar photocycloaddition with l-phenyl-l-trimethylsilyloxyethylene gave the corresponding 7-aryl derivatives 3a-e with the same regio- and stereo-chemistries in good yields. This stereochemical result of O-endo selectivity is consistent with the prediction obtained from the stereo-selection rule proposed for the enone-olefin photocycloaddition reaction. The reaction provides an efficient method for the synthesis of poly-functionalized cyclobutane derivatives.