Intramolecular C-H activation through gold(I)-catalyzed reaction of iodoalkynes
Pablo Morán-Poladura1, Eduardo Rubio, José M González
1Departamento de Química Orgánica e Inorgánica and Instituto Universitario de Química Organometálica "Enrique Moles", Universidad de Oviedo, C/Julián Clavería 8, Oviedo, 33006 (Spain).
Abstract:
The cycloisomerization reaction of 1-(iodoethynyl)-2-(1-methoxyalkyl)arenes and related 2-alkyl-substituted derivatives gives the corresponding 3-iodo-1-substituted-1H-indene under the catalytic influence of IPrAuNTf2 [IPr=1,3-bis(2,6-diisopropyl)phenylimidazol-2-ylidene; NTf2=bis(trifluoromethanesulfonyl)imidate]. The reaction takes place in 1,2-dichloroethane at 80 °C, and the addition of ttbp (2,4,6-tri-tert-butylpyrimidine) is beneficial to accomplish this new transformation in high yield. The overall reaction implies initial assembly of an intermediate gold vinylidene upon alkyne activation by gold(I) and a 1,2-iodine-shift. Deuterium labeling and crossover experiments, the magnitude of the recorded kinetic primary isotopic effect, and the results obtained from the reaction of selected stereochemical probes strongly provide support for concerted insertion of the benzylic C-H bond into gold vinylidene as the step responsible for the formation of the new carbon-carbon bond.
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