Gallium(III) halide promoted synthesis of 1,3,5-triaryl- 1,5-dihalo-1,4-pentadienes

GaCl3-Catalyzed Chloroacylation of Alkynes: A Simple, Convenient and Efficient Method to β-Chlorovinyl Ketones

“…4c Recently, Yadav et al reported a stereoselective condensation of phenylacetylene with benzaldehyde in the presence of gallium trihalides but no mechanism was proposed. 7 Yamaguchi et al has also developed an interesting GaCl 3 -promoted C2-olefination of aromatic hydrocarbons with silylacetylene, in which a novel organogallium intermediate was reported. 8 Considering the absence of b-silicon-stabilization to vinyl cation, we suggested the possibility of a C1-vinyl cation intermediate mechanism for the reaction (Scheme 2).…”

Metal‐Free Alkenylation of Salicylaldehydes with Boronic Acids: Synthesis of Skipped Dienes and 2H‐Chromenes

“…Reactions of aldehydes with alkynes in the presence of BX 3 (X=Cl, Br) [7] or TiCl 4 [8,9] to afford 1,5-dihalo-1,4-dienes were reported by Kabalka and co-workers. Subsequently, other metals such as FeCl 3 [10] and GaX 3 [11] (X = Cl, Br) were shown to promote similar transformations. The drawbacks of the reported reactions utilizing alkynes include the necessity to use stoichiometric amounts of strong Lewis acids.…”

Recent Applications of Niobium Catalysts in Organic Synthesis

“…Yadav and co-workers reported the use of GaCl 3 as catalyst to promote the synthesis of 1,3,5-triaryl-1,5-dihalo-1,4-pentadienes through the condensation between aldehydes and aryl acetylenes [24]. In most cases, the reactions afforded exclusively E,Z-isomers.…”