Regio‐ and Stereoselectivity of Ene Reactions: The Dimerization of Bicyclic 1,3‐Fused 2‐(Trimethylsilyl)cycloprop‐1‐enes

Abstract

Cycloalkenes proceed through bromination, dehydrobromination and dibromocarbene addition reactions to give tribromocyclopropanes 10 and 11. The treatment of tribromocyclopropanes 10 and 11 with 3 equiv. of methyllithium in diethyl ether at -78°C followed by treatment with trimethylsilyl chloride produce 8-(trimethylsilyl)bicyclo[5.1.0]oct-1(8)-ene (4) and 9-(trimethylsilyl)bicyclo[6.1.0]non-1(9)-ene (5). Both 4 and 5 undergo ene dimerization via the same steric isomer and an endo transition state to generate the stable adducts 6

Tetramerization of 3-Methyl-cyclopropene-3-carbonitrile: A Novel CN-Alder-ene Reaction

“…Recently, cyclopropene oligomerization processes have attracted attention as a possible route of synthesis of compounds containing several cyclopropane rings . Recent experimental works also demonstrated di-, tri-, and tetramerization of substituted cyclopropenes. – To our knowledge, in all cases reported, there was hydrogen at third cyclopropene carbon, thus allowing for Alder-ene reaction pathway. In the case of 1 , there is no such possibility.…”