Oxabicyclononene I (RR1 = CH2CH:CHCH2) underwent ozonolysis to give the diacid I (R = R1 = CH2CO2H) which was cyclized to bicyclic ketone I (RR1 = CH2COCH2). The ketone was cleaved with HI and P to give di(iodomethyl)cyclopentenone cis-II. The diol III (R2 = OH) was mesylated to give III (R2 = OSO2Me), which underwent iodine exchange and hydrolysis to form trans-II. Cyclization of cis-II with K2CO3 gave tricycloheptanone cis-IV, whereas bicyclohexenone V was formed when cis-II was treated with KHCO3 or DBU in refluxing C6H6. trans-IV was formed by treatment of trans-II or (iodomethyl)bicyclohexane trans-VI with K2CO3 on DBU, and trans-IV and trans-VI were formed from trans-II and KHCO3. Treating cis-VI with K2CO3 gave cis-IV whereas the former reacted with DBU to give V. Thus the reactivities of cis- and trans-II with base were affected by their stereochem. Reference Images Substance Image
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