title: Synthesis of isoquinolines and pyridines by the palladium-catalyzed iminoannulation of internal alkynes.
abstract: A wide variety of substituted isoquinoline, tetrahydroisoquinoline, 5,6-dihydrobenz[f]isoquinoline, pyrindine, and pyridine heterocycles have been prepared in good to excellent yields via annulation of internal acetylenes with the tert-butylimines of o-iodobenzaldehydes and 3-halo-2-alkenals in the presence of a palladium catalyst. The best results are obtained by employing 5 mol % of Pd(OAc)(2), an excess of the alkyne, 1 equiv of Na(2)CO(3) as a base, and 10 mol % of PPh(3) in DMF as the solvent. This annulation methodology is particularly effective for aryl- or alkenyl-substituted alkynes. When electron-rich imines are employed, this chemistry can be extended to alkyl-substituted alkynes. Trimethylsilyl-substituted alkynes also undergo this annulation process to afford monosubstituted heterocyclic products absent the silyl group.
authors.affiliation: Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
authors.forename: K R
authors.initials: KR
authors.lastname: Roesch
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: R C
authors.initials: RC
authors.lastname: Larock
mesh_terms: D000470:Alkaloids / Q000138:chemical synthesis; D000480:Alkynes / Q000737:chemistry; D002384:Catalysis; D007546:Isoquinolines / Q000138:chemical synthesis*; D010165:Palladium / Q000737:chemistry; D011725:Pyridines / Q000138:chemical synthesis*
chemical_list: D000470:Alkaloids; D000480:Alkynes; D007546:Isoquinolines; D011725:Pyridines; D010165:Palladium