| Abstract
| - The first successful example of the catalyzed Diels−Alder reaction of 1-methoxy-3-trimethylsiloxy-1,3-diene (Danishefsky's diene, 2a), giving the corresponding carbocyclic adducts, is described. Thereaction of (Z)-ethylideneacetoacetate 1a with 2a is catalyzed with lanthanide salts such as Yb(OTf)3at 0 °C, affording the corresponding 2-cyclohexenone 3a in good yield with complete integrity ofthe starting geometry of 1a. The thermal version of the same cycloaddition results in a decrease inthe cis arrangement of the 5-methyl and the 4-alkoxycarbonyl groups on 2-cyclohexenone. Thecatalyzed reaction of (E)-1a unexpectedly affords the cis-arranged 3a. The reaction path for thecatalyzed Diels−Alder reaction is postulated on the basis of these results.
|
