Abstract: 1,2-Dihydroquinolines, as the important structural motifs, have been broadly applied in synthetic intermediates and pharmaceuticals. Many synthetic methods for the preparation of 1,2-dihydroquinolines have been reported over the past few years. Recently, following the rapid development of organometallic chemistry, the metal-catalyzed functionalization of alkenes has gradually become the research focus of organic synthesis methodology, and the method was also applied in the synthesis of 1,2-dihydroquinolines. In this work, a method involving the Pd-catalyzed Wacker-type reaction and isomerization of alkene was developed to prepare a series of 1,2-dihydroquinoline derivatives. In the exploration and optimization of the reaction conditions, N,N-dimethylacetamide (DMA) was found to be the best solvent and palladium acetate (Pd(OAc)₂) was the best catalyst for our reactions. Then different additives (such as ligand, bases, acids and salts) were added to further optimize the reactions. The results show that pyridine or some ionic salts can inhibit the side reactions effectively, and 1,2-dihydroquinolines were prepared selectively. Among the ionic salts, sodium bromide (NaBr) was the best additive, therefore the amount of NaBr and reaction temperature were also optimized followed by the determination of the final standard conditions. Using NaBr at 40℃, the product was obtained in 94% yield for the standard substrate. The reactions proceeded smoothly for different substrates at the optimized standard conditions for both substrates bearing substituent groups at different positions on the benzene ring and substrates bearing different substituent groups. The yields were moderate for 3-substituted substrates, which may be due to the steric effect. For other substrates, the corresponding 1,2-dihydroquinolines can be obtained in high yields. The reaction mechanism was also proposed that an aryl-fused six-membered ring was formed firstly and then alkene was isomerized to obtain the 1,2-dihydroquinolines in the presence of palladium-hydrogen species. The released Pd was oxidized to Pd(Ⅱ) in the presence of benzoquinone (BQ) and oxygen to continue to the next catalytic cycle.