Diastereoselective [4 + 4]-photocycloaddition reactions of pyran-2-ones: rapid access to functionalized 5-8-5 skeletons.
Fused bicyclic pyran-2-ones with pendant furan side chains and an oxygenated stereogenic center adjacent to the pyranone ring oxygen were prepared via FeCl(3)-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. [reaction: see text]
Song
Dong
D
Department of Chemistry, University of Alberta, Edmonton, AB, Canada T6G 2G2.
McDonald
Robert
R
West
F G
FG