General procedure for the synthesis of 1-isoindolone-5-boronic acid pinacol ester from 5-bromo-2,3-dihydroisoindol-1-one and bipinacol ester: to an anhydrous solution of 5-bromo-2,3-dihydroisoindol-1-one (1 eq.) of dioxane (0.1 M) were added bis(pinacol) diboron (1.1 eq.), potassium acetate (3.5 eq.) and 1,1'-bis(diphenylphosphine ) ferrocene (dppf, 0.05 eq.). The reaction mixture was degassed with nitrogen for 20 minutes. Subsequently, dichloro(1,1'-bis(diphenylphosphino)ferrocene)palladium(II) (PdCl2(dppf), 0.05 eq.) was added and the mixture was degassed again for 5 minutes. Under nitrogen protection, the reaction mixture was heated to 70 °C for 2 hours and then warmed to 120 °C to continue the reaction for 16 hours. After completion of the reaction, the mixture was partitioned between ethyl acetate (EtOAc) and water. The aqueous phase was further extracted with ethyl acetate, the organic phases were combined, dried over anhydrous magnesium sulfate (MgSO4), filtered and concentrated under reduced pressure. The residue was dissolved in dichloromethane (CH2Cl2) and hexane was added to precipitate the product. The resulting suspension was filtered and the brown powder was collected and dried and used without further purification. The yield of the product 5-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-2,3-dihydroisoindol-1-one was 94% and purity was 76% with boric acid (13%) as the major impurity. Mass spectrometry analysis (LC-MS, ESP): m/z 260.4 [2M+H]+, retention time (R/T) = 3.51 min.
