[CH3:1][C:2]1[C:7]([CH3:8])=[CH:6][CH:5]=[CH:4][C:3]=1B(O)O.[CH3:12][C:13]1[CH:14]=[C:15]([CH:19]=[CH:20][C:21]=1[CH3:22])[C:16](O)=[O:17].C(OC(OC)=O)(OC)=O.C(=O)([O-])[O-].[K+].[K+]>[Pd].O1CCOCC1.O>[CH3:1][C:2]1[C:7]([CH3:8])=[CH:6][CH:5]=[CH:4][C:3]=1[C:16]([C:15]1[CH:19]=[CH:20][C:21]([CH3:22])=[C:13]([CH3:12])[CH:14]=1)=[O:17]
To a 250 ml 3-necked round-bottom flask, 2,3-dimethylphenylboronic acid (3.6 g, 24 mmol), 3,4-dimethylbenzoic acid (3.0 g, 20 mmol), a selected palladium catalyst (0.6 mmol), dimethyl dicarbonate (2.7 g, 30 mmol) and potassium carbonate (6.22 g, 45 mmol) were mixed with 150 ml of dry dioxane. The reaction mixture was heated at 80° C. overnight to become a viscous reaction mixture. 20 ml of water was added to dissolve the heterogeneous reaction mixture, and dioxane was evaporated to dryness. The aqueous solution as extracted with 20 ml of ethyl acetate, dried over anhydrous magnesium sulfate and then evaporated to dryness. The crude product was purified by silica gel column chromatography eluted by hexane/ethyl acetate=20/80 to afford 2.0 g (33%) of the product.
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