STEREOSELECTIVE EPOXIDATION OF CYCLOHEXA-ANELLATED TRIQUINACENES WITHIODINE SILVER(I) OXIDE AS COMPARED TO M-CHLOROPERBENZOIC ACID/

Iodine/silver(I) oxide (I-2/Ag2O) reacts highly stereoselectively in t he single, double, and triple anti epoxidation of the spherical 1,4,7- triene, 0-methyl-2,3:5,6:8,9-tris(cyclohexano)triquinacene 1. All of t he three epoxides 3, 4, and 5 obtained with this reagent contain the e poxy groups at the convex side of the triquinacene framework. The ster eochemical course of the epoxidation with I-2/Ag2O is clearly distinct from that observed with m-chloroperbenzoic acid (MCPBA), which gives the same monoepoxide (3) but exclusively anti,syn di- and triepoxides (6-8) bearing at least one epoxy group at the concave side of the triq uinacene framework. Epoxidation of the related three-fold 1,4-cyclohex adiene, tris(cyclohexeno)triquinacene 2, with MCPBA occurs similarly t o the conversion of 1, whereas I-2/Ag2O reacts with high regioselectiv ity at the less electron-rich peripheral double bonds of 2 giving trie poxides 12 and 13. The molecular structure of triepoxide 8 has been el ucidated in detail by X-ray crystal structure analysis.