Cyclopentadiene peroxide synthesis

We developed a convenient synthesis of 3-cyclopentenyl hydroperoxide via hydro-boration and autoxidation of cyclopentadiene, and bromination proceeded smoothly to afford 32 40). Ring closure with silver trifluoroacetate (Eq. 26) afforded a 5-bromo-2,3-dioxabicyclo[2.2.1]heptane 34 (6%) and a 5-trifluoroacetoxy-2,3-dioxabicyclo-[2.2.1]heptane 35 (14%), and it was shown independently that 34 is rapidly converted into 35 by reaction with Ag02CCF3. To avoid the trifluoroacetate bromide substitution that accompanies and competes with the dioxabicyclization, 32 was treated with silver oxide and this slowly yielded an isomeric 5-bromo-peroxide 33 (42 %) (Eq. 26). 

The addition of singlet oxygen to the furanolactone (166) gave a quantitative yield of the pseudo-acids (167) and (168) which were converted into the antitumour compound camptothecin (169) in three steps (Scheme 48). Other important uses of the Diels-Alder addition of singlet oxygen to dienes are in the synthesis of cw-l,4-dihydroxycyclopentene from cyclopentadiene/ and in the preparation of analogues of prostaglandin endo-peroxide. ... 

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