Diastereoselective [4+4]-photocycloaddition reactions of pyran-2-ones: Rapid access to functionalized 5-8-5 skeletons

摘要

Fused bicyclic pyran-2-ones with pendant furan side chains and an oxygenated stereogenic center adjacent to the pyranone ring oxygen were prepared via FeCl3-catalyzed Michael addition. Irradiation furnished the corresponding lactone-bridged tricyclic [4+4]-cycloadducts with good facial selectivity. Surprisingly, the major isomer resulted from approach of the furan from the same face as the protected alcohol.