Catalyzed Diels-Alder reaction of alkylidene- or arylideneacetoacetates and Danishefsky's dienes with lanthanide salts aimed at selective synthesis of cis-4,5-dimethyl-2-cyclohexenone derivatives.
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. The reaction of (Z)-ethylideneacetoacetate 1a with 2a is catalyzed with lanthanide salts such as Yb(OTf)(3) at 0 degrees C, affording the corresponding 2-cyclohexenone 3a in good yield with complete integrity of the starting geometry of 1a. The thermal version of the same cycloaddition results in a decrease in the cis arrangement of the 5-methyl and the 4-alkoxycarbonyl groups on 2-cyclohexenone. The catalyzed reaction of (E)-1a unexpectedly affords the cis-arranged 3a. The reaction path for the catalyzed Diels-Alder reaction is postulated on the basis of these results.
Inokuchi
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T
Department of Bioscience and Biotechnology, Faculty of Engineering, Okayama University, Okayama 700-8530, Japan. inokuchi@biotech.okayama-u.ac.jp
Okano
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M
Miyamoto
T
T