Transition metal control in the reaction of alkyne-substituted phenyl iodides with terminal alkynes: Sonogashira coupling vs cyclic carbopalladation

• Published in: Tetrahedron Vol. 58; no. 44; pp. 9007 - 9018
• Main Authors: Teplý, Filip, Stará, Irena G., Starý, Ivo, Kollárovič, Adrian, Šaman, David, Fiedler, Pavel
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 28.10.2002; Elsevier
• Subjects: alkynes; aryl halides; Chemistry; Chemistry, Organic; coupling reactions; cyclisation; Physical Sciences; Science & Technology; cyclisation; aryl halides; alkynes; coupling reactions; VINYL; PALLADIUM; CATALYZED CASCADE CYCLIZATION; CONSTRUCTION; CHEMISTRY; TRIYNES; PRECURSORS; MOLECULES
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/S0040-4020(02)01154-7

Reaction between terminal alkynes and phenyl iodides bearing a tethered alkyne unit can be effectively controlled by the nature of a transition metal catalyst. Whereas the use of Pd(0)/Cu(I) promotes the expected Sonogashira coupling to give phenyl alkynes, the absence of the copper co-catalyst triggers a palladium-mediated cyclisation providing 1,2-dihydroacenaphthylene, 1 H,3 H-benzo[ de]isochromene, (1 Z)-1-(2-propynylidene)-2,3-dihydro-1 H-indene and (4 E)-4-(2-propynylidene)-3,4-dihydro-1 H-isochromene derivatives. In the latter Pd-catalysed two-component process, the product distribution depends on the structure of alkyne-substituted phenyl iodides, terminal alkynes and secondary amines used as solvents. The proposed reaction mechanism reflects a competitive formation of intermediary σ-(acetylide) vs π-alkyne Pd(II) complexes. Graphic