Lewis Acid or Bronsted Acid Catalyzed Reactions of Vinylidene Cyclopropanes with Activated Carbon-Nitrogen, Nitrogen-Nitrogen, and Iodine-Nitrogen Double-Bond-Containing Compounds

Lewis acid or Bronsted acid catalyzed reactions of vinylidene cyclopropanes (VDCPs). 1, with activated carbon-nitrogen. nitrogen-nitrogen, and iodine-nitrogen double-bond-containing compounds have been thoroughly investigated. We found that pyrrolidine and 1,2,3,4-tetrahydroquinoline derivatives can be formed in good yields in the reactions of VDCPs I with ethyl (arylimino)acetates 2 by a [3+2] cycloaddition or intramolecular Friedel-Crafts reaction pathway. Based on these results. we found that activated carbon-nitrogen and nitrogen-nitrogen double-bond-containing compounds, such as N-toluene-4-sulfonyl (N-Ts) imines 5 and diisopropylazodicarboxylate (7), can also react with VDCPs 1 to give [3+2] cycloaddition products in moderate to good yields in the presence of a Lewis acid. When N-tert-butoxycarbonyl aldimine 9 was used as the substrate. six-membered cycloaddition products 10 and 11 were formed in moderate yields in the presence of a Bronsted acid, trifluoremethanesulfonic acid (TfOH). The reactions of VDCPs 1 with N-Ts-iminophenyliodinane (12) were also carried Out in the presence of (CuOTf)2 center dot C6H6 and it was found that nitrogen-containing indene derivatives 13 were obtained, rather than the aziridination products. Plausible mechanisms for all of these transformations are discussed, based on the obtained results.