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

Abstract

At elevated temperatures 3-methyl-cyclopropene-3-carbonitrile 1 was found to tetramerize giving compound 2 (3-methyl-2,3-bis(2-t-methyl-2-c-cyanocyclopropyl)-1-(2-t-methyl-2-c,3-c-dicyanocyclopropyl)-cyclopropene) in good yields. This is the first example of Alder-ene type oligomerization of a 3,3-disubstituted cyclopropene. On the basis of the product geometry and stereoselective character of the reaction, a mechanism of formation of 2 involving CN-Alder-ene reaction was proposed. DFT modeling of the mechanism has shown that the CN-Alder-ene reaction is possible as a stepwise process involving a biradical intermediate.

π-Stacking-Controlled Dearomatic Sulfur-Shifted Ene Reaction of Ketenes and Polycyclic Arylthiiranes: Access to Areno[d]-ε-thiolactones

“…To verify the proposed mechanism and to exclude the possible pathway B, the reaction of phenoxyacetyl chloride (1a) and styrylthiirane (6) was performed. The reaction should favor the [3,3]-sigmatropic shift after the nucleophilic addition of thiirane 6 to ketene A because the [3,3]-sigmatropic shift need not to undergo a dearomatic process.…”

“…The metals include Pd, Zn, Ru, Zr, Ti, Na, K, etc. (Scheme b). , However, for ene reactions involving non-H and nonmetal shifts, to the best of our knowledge, only a carbon-shifted ene reaction with the cyano shift was occasionally observed in the tetramerization of 3-methylcyclopropene-3-carbonitrile (Scheme c) …”

“…4,5 However, for ene reactions involving non-H and nonmetal shifts, to the best of our knowledge, only a carbonshifted ene reaction with the cyano shift was occasionally observed in the tetramerization of 3-methylcyclopropene-3carbonitrile (Scheme 1c). 6 Ring-strain-promoted ring opening, ring expansion, and annulation reactions of three-membered saturated heterocycles are an attractive way to introduce three-atom fragments in starting materials. 7 The ring expansions and annulations can construct common, medium, and macrocyclic compounds.…”

Recent developments of cyclopropene chemistry

“…A mechanism of formation of 102 involving CN-Alder-ene reaction was proposed by the author and the mechanism studied by DFT methods has shown that the CN-Alder-ene reaction is possible as a stepwise process involving a biradical intermediate. 79 3.1.2 Carbometalation reactions. Directed carbometalation reactions of cyclopropenes are powerful and versatile approachs for the construction of functionalized cyclopropanes.…”