“…81 As illustrated in couplings with 3-hydroxy-2-oxindoles, β-substituted acrylic esters provides spiro-γ-butyrolactones as single diastereomers. 81 Remarkably, the cycloadditions may be conducted in oxidative, redox-neutral or reductive modes using diols, ketols or diones, respectively, as reactants. To illustrate, ethyl acrylate reacts with hydrobenzoin, benzoin or benzil to form an identical γ-lactone.…”