Phosphine-catalysed (4+1) annulations of β′-acetoxy allenoate with β,γ-unsaturated carbonyl compounds

While β,γ-unsaturated carbonyl compounds have been widely used as γC- or αC-nucleophiles, their potential αC,αC-bisnucleophilic reactivity is still underdeveloped. Herein, a phosphine-catalysed (4+1) annulation of β′-acetoxy allenoate and a β,γ-unsaturated carbonyl compound is reported, wherein β′-acetoxy allenoate is the 1,4-biselectrophilic component while the β,γ-unsaturated carbonyl compound serves as an αC,αC-bisnucleophile. The process not only provides a new reaction mode of β,γ-unsaturated carbonyl compounds under mild conditions but also broadens the scope of Lewis base-catalysed annulation of acetoxy allenoate.