Endoperoxides diepoxides, rearrangement

Various applications of the endoperoxide-epoxide rearrangements in the multistep total synthesis of natural products are reported in the literature, for example, the synthesis of stemolide, a natural syn-diepoxide with antileukemic activity. A photochemical route from arenes to inositol intermediates was... 

The bicyclic peroxide 11 was prepared via diimide reduction of the endoperoxide derived from spirocyclopentadiene (Eq. 8)21>. As before, at elevated temperature the labile endoperoxide rearranges into diepoxide and ketoepoxide,22) but diimide reduction at —78 °C allows trapping leading to the highly strained bicyclic peroxide 11. 

Arylsubstituted cyclopentadienes such as 1,2,3,4-tetraphenylcyclo-pentadiene (369) give rise to isolable endoperoxides249 which can be thermally rearranged to m-diepoxides. From the corresponding fulvene derivative (372) only the diepoxide 374 was isolated which probably originates from a thermally unstable endoperoxide 37i.249,250... 

Conjugated cycloalkadienes4l3 17 are converted to bicyclic endoperoxides that may undergo thermal or photochemical rearrangement to yield diepoxides.374-377 1,3-Cyclopentadiene and 1,3-cyclohexadiene give endoperoxides exclusively. The first synthesis of the naturally occurring ascaridol (52) was also carried out in this way 418,419... 

As might be anticipated, when an O—O bond is cleaved in the presence of a radical trap, such as a double bond, the course of the reaction becomes quite different. Thus, thermolysis of bridged 3,6-dihydro-l,2-dioxins (1,4-endoperoxides) such as (146) causes rearrangement to c/s-diepoxides (147) <81T1825). 

The photooxide of naphthalene (74) on treatment with triphenylphosphine is converted to naphthalene 1,2-oxide (45).40 The photooxide of anthracene (75) is converted to syw-anthracene[4a,10 9,9a]diepoxide (76) in 78% yield by means of an interesting photochemical rearrangement.41 The endoperoxide of... 

Thermal rearrangement of endoperoxides of bicyclic dienes gives syn-diepoxides [9b,33a], which are sometimes accompanied by epoxyketones... 

The p-peroxide 84 was obtained by methylene blue-sensitized photooxygenation of diene 83 together with its a-isomer (2 1 9,13-a p) and was separated by silica gel chromatography. Diepoxides are the thermally rearranged products of a.a -unsubstituted or alkylsubstituted furan endoperoxides [59,60d,g]. 

Rearrangement of 1,4-endoperoxides. Co l PP catalyzes the rearrangement of 1,4-endoperoxides to. syn-l, 2 3,4-diepoxides at - 78 Neither me.w-tetraphenylporphine nor zinc mexo-tetraphenylporphine catalyzes this rearrangement. N,N.N, N -Tetramethyl-ethylenediamine catalyzes the reaction, but only very slowly. The yields from the catalyzed reaction are much higher than those obtained by thermolysis. 

Addition to 3,S-cyeloheptadiene-l-oi (1). Photogenerated singlet oxygen (hematoporphyrin hydrochloride, sensitizer) adds to 1 in a stereoselective manner isyn to OH) to give mainly the endoperoxide 2. The reaction of the acetate of 1 is less selective because the acetyl derivative of 3 rearranges readily under both photolytic and thermal conditions to a diepoxide. Under the same conditions the acetyl derivative of 2 is relatively stable. ... 

Excitation of non-fluorescent endoperoxide of mesodiphenylhelian-threne (370) rearranged to highly emissive diepoxide (371) (Scheme 77). °... 

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