Catalytic Synthesis of Phthalide Derivatives via Asymmetric Bromolactonization of Stilbene‐type Carboxylic Acids using N,N‐Dibenzyl Diaminomethylenemalononitrile as Organocatalyst

The asymmetric 5-exo bromolactonization of stilbene-type carboxylic acids could be achieved using a N,N-dibenzyl diaminomethylenemalononitrile organocatalyst with high yields and excellent enantioselectivities (up to 92% ee) of the corresponding phthalide derivatives. This is the first report where the successful synthesis of the phthalide derivatives as the main product, with high optical purity, could be achieved using the asymmetric 5-exo bromolactonization of the stilbene-type carboxylic acids with various substituents.