Palladium(II)-Catalyzed Synthesis of Functionalized Indenes from o-Alkynylbenzylidene Ketones

An efficient method for the synthesis of functionalized indenes from o-alkynylbenzylidene ketones under palladium(II) catalysis was developed. The reaction is initiated by trans-nucleopalladation of alkynes, followed by conjugate addition and quenched by protonolysis of the carbon palladium bond. With acetate and halide ions as nucleophiles, 3-acetoxy- and 3-halogen-substituted indenes could be obtained in high yields.