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Palladium-Mediated Functionalization of Heteroaromatic Cations:  Comparative Study on Quinolizinium Cations

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journal contribution
posted on 13.10.2006, 00:00 by Domingo García-Cuadrado, Ana M. Cuadro, Bernardo M. Barchín, Ana Nuñez, Tatiana Cañeque, Julio Alvarez-Builla, Juan J. Vaquero
An efficient palladium-catalyzed cross-coupling reaction on heteroaromatic cations is described. A comparative study of the Stille and Suzuki reactions shows that only the Stille reaction is able to produce an efficient C−C bond formation between any of the four isomeric bromoquinolizinium bromides and a variety of stannanes. In the presence of the catalysts Pd(PPh3)4 or Pd2(dba)3P(o-Tol)3, vinyl, ethynyl, aryl, and heteroaryl groups are successfully incorporated into the quinolizinium system in satisfactory yields under mild reaction conditions. This procedure represents a marked improvement on the functionalization of this class of heteroaromatic cation.