Table 1 Initial attempt and optimization conditions regarding metal catalysts and ligands

^aReaction conditions: the reaction was carried out with 1 (0.25 mmol), 2 (0.8 mmol), 3 (0.067 mmol), palladium catalyst (4 mol%), K₂CO₃ (2.0 equiv) in 2 mL of mixed solvent (DCM:H₂O = 5:1) at 50 °C for 12 h. ^bReaction conditions: the reaction was carried out with 1 (0.25 mmol), 2 (0.8 mmol), 3 (0.067 mmol), iron catalyst (10 mol%), Cs₂CO₃ (1.5 equiv) in 2 mL 1,4-dioxane at 80 °C for 12 h. ^cReaction conditions: the reaction was carried out with 1 (0.25 mmol), 2 (0.8 mmol), 3 (0.067 mmol), copper catalyst (10 mol%), ligand (10 mol%), K₂CO₃ (3.0 equiv) in 2 mL toluene at 80 °C for 12 h. ^dReaction conditions: the reaction was carried out with 1 (0.25 mmol), 2 (0.8 mmol), 3 (0.067 mmol), nickel catalyst (10 mol%), ligand (15 mol%), K₂CO₃ (2.0 equiv) in 2 mL DMA at 70 °C for 24 h. ^eYields were determined by gas chromatography (GC) using n-dodecane as the internal standard. Unless otherwise stated, the desired polysubstituted 1,3-dienes were obtained with regioselectivity greater than 95:5 (the ratio of 5:5’ was greater than 95:5), and the regioselectivity was detected by ¹H NMR analysis of desired products or GC analysis of desired products. M = Metal catalysts, L = Ligand, nd = not detected.

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