How is (3E)-6-Bromo-3-[6-bromo-1-(2-ethylhexyl)-2-oxo-1,2-dihydro-3H-indol-3-ylidene]-1-(2-ethylhexyl)-1,3-dihydro-2H-indol-2-one (CAS: 1147124-23-9) typically synthesized?

The compound is typically synthesized via a multi-step process involving the reaction of bromoalkyl indoles with 2-ethylhexyl acrylate. The synthesis involves the condensation of 2-ethylhexyl acrylate with 6-bromo-1-(2-ethylhexyl)-2-oxo-1,2-dihydro-3H-indol-3-one, followed by the formation of the indolone structure. The reaction is carried out under mild conditions, using a catalytic amount of a Lewis acid such as zinc chloride as a catalyst. The yield of the final product is around 70-80%, and the reaction is selective with high purity.