Lewis Acid or Brønsted Acid Catalyzed Reactions of Vinylidene Cyclopropanes with Activated Carbon–Nitrogen, Nitrogen–Nitrogen, and Iodine–Nitrogen Double‐Bond‐Containing Compounds

Abstract

Lewis acid or Brønsted 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 1 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 Brønsted acid, trifluoromethanesulfonic acid (TfOH). The reactions of VDCPs 1 with N-Ts-iminophenyliodinane (12) were also carried out in the presence of (CuOTf)(2)C(6)H(6) 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.

Advances in the Chemistry of Tetrahydroquinolines

“…For instance, treatment of imines 459 and allenes 460 with 50 mol % of BF 3 ·OEt 2 afforded the polysubstituted tetrahydroquinoline derivatives 461 bearing an exocyclic double bond at C-3 position in good yields and under mild experimental conditions (Scheme ) . A mechanism was also proposed involving carbocation intermediates and the study was subsequently elaborated as a full paper …”

Synthesis of Chiral Trispirocyclic Oxindoles via Organic-Base/Au(I)-Catalyzed Sequential Reactions

“…To probe into the mechanism of key HDA reaction of ketimine 2 as the heterodiene, − we carried out DFT calculations using M06-2x/cc-pVDZ method by using 2a as the substrate (computational details were given in the Supportng Information). Both concerted and stepwise mechanisms were evaluated.…”

Synthesis of Benzofulvenes through Rhodium-Catalyzed Transannulation of Enynyl Triazoles

“…Their importance has encouraged the development of new synthetic approaches for benzofulvenes. As a result, a large number of synthetic methods have been demonstrated for the synthesis of benzofulvenes, including the radical or Pd-catalyzed cyclization of enediynes (Scheme , a ), metal-catalyzed or photochemical cyclization of enynes ( b ), Pd-catalyzed cyclization of homoallylic acetates or 1,3-dienes derived from Morita-Baylis-Hillman adducts ( c ), thermal or photochemical cyclization of enyne-allenes ( d ), domino Heck C–H activation reaction of unsymmetrically substituted [3]­cumulenes ( e ), (CuOTf) 2 ·C 6 H 6 -catalyzed reactions of vinylidene cyclopropane with N -Ts-imino­phenyl­iodinanes ( f ), Au-catalyzed isomerization of cyclopropenes ( g ), Ag and Brønsted acid catalyzed Nazarov-type cyclization ( h ), and Pd-catalyzed tandem reactions of 1-(2,2-dibromovinyl)-2-alkynyl­benzenes with arylboronic acids ( i ) . Due to its significance, it is still of considerable interest and necessity to develop efficient synthetic methods for functionalized benzofulvenes, especially in the field of organometallic chemistry and materials science …”