Brønsted acid TfOH-mediated [3 + 2] cycloaddition reactions of diarylvinylidenecyclopropanes with nitriles

Diarylvinylidenecyclopropanes undergo a [3 + 2] cycloaddition reaction with MeCN in the presence of Brønsted acid TfOH to give the corresponding 3,4-dihydro-2 H-pyrrole derivatives 2 in moderate to excellent yields under reflux within a short time. As for the diarylvinylidenecyclopropane substrate containing a strongly electron-donating methoxy group on the benzene ring, the reaction leads to the formation of a different type of 3,4-dihydro-2 H-pyrrole derivatives 4 under the same conditions.

Lewis Acid Catalyzed Rearrangement of Vinylcyclopropenes for the Construction of Naphthalene and Indene Skeletons

[reaction: see text] The choice of Lewis acid catalyst can result in dramatic differences in the chemoselectivity of the rearrangement reactions of vinylcyclopropenes. When BF3.OEt2 was used as the catalyst, naphthalenes were formed. However, when Cu(OTf)2 was used as the catalyst, indenes were obtained.

Reactions of Vinylidenecyclopropanes with Diphenyl Diselenide in the Presence of AIBN and Further Transformation To Produce New Naphthalene Derivatives

The reactions of vinylidencyclopropanes 1 with diphenyl diselenide 2 in the presence of AIBN produced the corresponding products 4 or 5 in moderate to good yields under mild conditions. The transformation of 4 to the corresponding methylenecyclopropanes 6 was achieved by treatment with hydrogen peroxide (H2O2) in toluene, and these were further transformed to the corresponding naphthalene derivatives 7 by treatment with 30 mol % of TfOH in dichloromethane.