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45.10.8.1.1.1 Variation 1: Condensation Reactions with Active Methylene Compounds Initiated by Acetic Anhydride

DOI: 10.1055/sos-SD-045-00354

Ito, S.; Morita, N.Science of Synthesis, (201045463.

8,8-Dicyanoheptafulvenes 133, including 2,6-disubstituted derivatives, are prepared by reactions of the corresponding tropones 132 with malononitrile in refluxing acetic anhydride (Scheme 40).[‌164‌] Related to this method are the reactions of methyl cyanoacetate with substituted and annulated tropone derivatives.[‌165‌‌168‌] Steric hindrance in 2-substituted tropones 134 is thought to be the cause for nucleophilic attack further away from the substituent. Therefore, condensation of 2-substituted tropones 134 with active methylene compounds such as methyl cyanoacetate gives isomeric mixtures of 1-, 2-, and 3-substituted heptafulvenes 135, 136, and 137 (Scheme 40).[‌165‌]

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