Accessing polysubstituted 2-cyclopentenones <i>via</i> base-mediated annulation of β-keto esters and phenacyl bromides

A transition metal-free method is demonstrated for the synthesis of polysubstituted 2-cyclopentenone compounds, which involves the direct annulation of phenacyl bromide with β-keto esters in a single step. This process proceeds through a base-mediated S_N2 nucleophilic substitution, followed by an intramolecular aldol condensation, resulting in the formation of three C-C bonds and one ring in a cascade manner. The experimental results achieved a record high yield of highly substituted diverse 2-cyclopentenone analogues, which exhibit very good structural resemblance to biologically significant natural compounds.