Preparation of tetrahydrodibenzocyclooctene lignans and spirodienones by hypervalent iodine oxidation of phenolic dibenzylbutyrolactones

Article abstract of DOI:10.1016/0040-4020(95)00960-4

Treatment of the dibenzylbutyrolactone 18 with PhI(OCOCF₃)₂ in trifluoroethanol gives as the major product either the spirodienone 28 or the tetrahydrodibenzocyclooctene 29, depending upon the length of time allowed for the reaction. Reaction of a second dibenzylbutyrolactone 19 under the same conditions gives the products 33, 34, 36 and 38, while 20 gives 43 directly. These reactions provide the first syntheses of spirodienones such as 28 and 33, which have been postulated as intermediates in the biosynthesis of tetrahydrodibenzocyclooctene lignans.