Catalytic γ-Position-Selective Reactions of (2-Oxopropyl)phosphonates with Aldehydes to Afford γ,δ-Unsaturated β-Ketophosphonates

Abstract

Catalytic formal aldol condensation reactions between β-ketophosphonates and arylaldehydes, in which the C-C double bond formation occurs at the γ-position of the β-ketophosphonate, are reported. The reactions were performed in the presence of a catalyst system composed of <i>p</i>-anisidine and trifluoroacetic acid under mild conditions. Mechanistic investigations suggest that a Mannich reaction followed by elimination results in the formation of the γ,δ-unsaturated β-ketophosphonate. Although the β-ketophosphonate has an active methylene group, the bond formation occurred selectively at the γ-position of the β-ketophosphonate.