| Abstract
| - The potential dual behavior as dienes and dienophiles of the diene moieties of masked o-benzoquinones (MOBs) 10a−e−12a−e, generated upon oxidation of 2-methoxyphenols 1−3 withBTIB in the presence of appropriate dienols, in their intramolecular Diels−Alder (IMDA) reactionshas been examined. The IMDA reactions of MOBs 10a−d, 11a,b,d, and 12a,b,d resulted in highlyfunctionalized oxatricyclic compounds 18a−d, 19a,b,d, and 20a,b,d, respectively, with concomitantformation of cis-decalin derivatives 21a−d, 22a,b,d, and 23a,b,d in a highly regio- and stereoselective manner. However, the MOBs 10e−12e provided exclusively oxatricyclic compounds 18e−20e. The formation of cis-decalins in these IMDA reactions illustrates the dienophilic character ofMOBs, in addition to their behavior as dienes. The ratio of the two cycloadducts obtained in eachreaction as a result of the dual character of MOBs depends on the nature and/or position of thesubstituents on both the cyclohexadienone moiety and the added 2,4-dienol. The majority of thecycloadducts resulted from the diene property of MOBs in intramolecular Diels−Alder reactionssmoothly underwent Cope rearrangement to furnish cis-decalins as sole products in excellent toquantitative yields that provides a short and efficient entry to polyfunctionized cis-decalins from2-methoxyphenols. Furthermore, the variation of dienophilic and diene characters of MOBs in theIMDA reactions with the electron-donating or electron-withdrawing substituent of both cyclohexadienone moiety and the added conjugated acyclic diene or 2,4-dienol has been studied in detail.
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