Trapping of Diacceptor-Substituted Methylenecyclopropanes with Isocyanides - A Further Application of the Principle of the Twofold Nucleophilic Substitution at a Cyclopropane
Trapping of Diacceptor-Substituted Methylenecyclopropanes with Isocyanides - A Further Application of the Principle of the Twofold Nucleophilic Substitution at a Cyclopropane
Trapping of Diacceptor-Substituted Methylenecyclopropanes with Isocyanides - A Further Application of the Principle of the Twofold Nucleophilic Substitution at a Cyclopropane
Unstable 2-cyclopropylidene-1,3-diones 3 can be trapped by isocyanides 8 to give [4 + 1]-cycloadducts 9 and 12. In the case of Meldrum's acid, as the dioxo component, spirotricyclic imides 15 are isolated due to an easy degradation of the primary cycloaddition products 14 in methanol. Subsequent reactions are described for the [4 + 1]cycloadducts leading to a cyclopropanecarboxamide 19b or to a phenylamino-substituted furan 20/21. Trapping of 3 by isocyanides 8 represents a novel second step in the concept of the twofold nucleophilic substitution at a cyclopropane.