Trimethylaluminium (0.362 mL, 0.72 mmol) was added to a solution of pyridin-2-amine (68.1 mg, 0.72 mmol) in toluene (8 mL) at 0° C. under nitrogen. The reaction mixture was stirred at 0° C. for 20 mins and then (S)-methyl 3-(3-(tert-butyldimethylsilyloxy)azetidin-1-yl)-2-(1-(2,6-dichlorophenyl)-1H-pyrazolo [3,4-d]pyrimidin-4-yloxy)propanoate (Intermediate BJ1) (200 mg, 0.36 mmol) in toluene (4 mL) was added. The reaction mixture was allowed to warm to room temperature and then heated at reflux under nitrogen for 4 hours. The reaction mixture was allowed to cool to room temperature and the concentrated. The residue was neutralised to pH 7 with citric acid (1M, aq) and then diluted with water and DCM (50 mL). The organic layer was separated and the aqueous layer re-extracted with DCM (30 mL). The combined organics were dried (MgSO4), filtered and evaporated. The crude product was purified by flash silica chromatography, elution gradient 20 to 50% EtOAc in isohexane to afford the product (151 mg, 67.9%).
