A 500 ml glass pressure vessel was charged with tert-butyl-dimethyl-[2,3,5-trifluoro-6-(1H-pyrazolo[3,4-b]pyridin-3-yl)-4-pyridyl]silane (26.80 g, 73.53 mmol), (2R)-3-methyl-2-piperazin-2-yl-butan-2-ol (19 g, 110.3 mmol), THF (53 mL) and imidazol-1-yl-trimethyl-silane (51.57 g, 53.72 mL, 367.7 mmol). An identical experiment was run in parallel. The containers was sealed and the mixture was heated and stirred at 95° C. overnight. Lc/Ms after this time showed a mixture consisting of 73% of the desired (S,R)-diastereoisomer and 18% of the (R,R)-diastereoisomer. Both reaction mixtures were cooled, combined and diluted with EtOAc (500 ml). The solution was washed with saturated sodium bicarbonate (2×200 ml). The combined aqueous layers are extracted 3 times with ethyl acetate (200 ml). The combined organics were washed with brine (200 ml), dried over MgSO4, filtered and concentrated in vacuo to give 163.874 g of viscous brown oil. The diastereoisomers were separated on silica gel, eluting with 10-95% ethyl acetate in petroleum ether containing 2% triethylamine). This gave the required (S,R) -diastereoisomer as an orange foam (60.1 g, 69%); 1H NMR (CDCl3) 0.001 (9H, s), 0.32 (6H, s), 0.76-0.84 (9H, m), 1.11 (4H, m), 1.45 (4H, m), 1.72 (1H, m), 1.90 (1H, s), 2.61 (1H, m), 2.74 (2H, m), 2.97 (1H, m), 3.11 (1H, m), 3.64 (1H, m), 3.82 (1H, m), 3.96 (1H, m), 7.09 (1H, m), 8.48 (1H, m), 8.74 (1H, m), 11.31 (1H, brs); 19F NMR (decoupled) −113.45, −108.39; MS ES(+) 589.3 (M+1). The (R,R)-diastereoisomer was isolated as an orange foam (22%); 1H NMR (CDCl3) 0.001 (9H, s), 0.33 (6H, s), 0.72-0.88 (10H, m), 1.07 (3H, m), 1.45 (5H, m), 1.86 (1H, m), 2.54 (1H, m), 2.74 (2H, m), 2.94 (1H, m), 3.07 (1H, m), 3.63 (1H, m), 3.73 (1H, m), 3.96 (1H, m), 7.04 (1H, m), 8.46 (1H, m), 8.69 (1H, m), 11.35 (1H, brs); 19F NMR (decoupled) −113.78, −108.4; MS ES(+) 589.3 (M+1).
