Preparation of a,b-Unsaturated Ketones from Alkynes and Aldehydes

A cation exchange resin catalyzed coupling reaction of alkynes and aldehydes is reported. Thus, the reaction of monosubstituted alkynes 1 (R¹ = Alk, Ar) and aldehydes 2 (R² = H, Alk, Ar) was carried out with Amberlyst-15 to give the corresponding products 3 in 70-90% yield. The coupling of disubstituted alkynes 4 (R³ = Alk) with formaldehyde 5 was performed under similar conditions to afford a mixture of vinyl ketones 6 and 1,3-dioxane 7 in 78-85% yield with 2:1 selectivity.