title: Probing the nature and extent of stabilization within foiled carbenes: homoallylic participation by a neighboring cyclopropane ring.
abstract: Oxadiazoline 6 was synthesized to generate endo-tricyclo[3.2.1.0(2,4)]octan-8-ylidene (3) by either photolysis or thermolysis. Diastereomer 6a thermally decomposed twice as fast as 6b. Carbene 3 was trapped stereoselectively by acrylonitrile and diethylamine in high yields. It behaved as a nucleophilic carbene with electron-poor alkenes, like acrylonitrile, but as an electrophile with very electron-rich species, such as diethylamine. However, when the reactions were performed in cyclohexane and cyclohexene, isomerization of 3 was favored. Replacement of the double bond in 7-norbornenylidene (1) by the single bond in the endo-fused cyclopropane unit of carbene 3 led to similar outcomes. Carbene 3 rightfully belongs to the family of foiled carbenes.
authors.affiliation: Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, A-1090 Vienna, Austria.
authors.forename: Ingrid Malene
authors.initials: IM
authors.lastname: Apeland
authors.forename: Hanspeter
authors.initials: H
authors.lastname: Kählig
authors.forename: Eberhard
authors.initials: E
authors.lastname: Lorbeer
authors.forename: Udo H
authors.initials: UH
authors.lastname: Brinker