Reaction Steps
N-(4-Methoxybenzyl)-5-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1-tosyl-1H-indol-5-yl)-1,3,4-oxadiazol-2-amine (0.200 g, 0.333 mmol), 2-bromo-5-(methylsulfonyl)pyridine (0.118 g, 0.500 mmol) (Acme Bioscience Inc., Palo Alto, Calif.), Xphos (Strem Chemicals, Newburyport, Mass., 9.5 mg, 0.020 mmol), Pd2(dba)3 (Strem Chemicals, Newburyport, Mass., 9.2 mg, 9.99 μmol) and potassium phosphate (0.212 g, 0.999 mmol) were weighed into a 5 mL glass microwave tube. The tube was purged with argon and the solids were treated with dioxane (2.0 mL) and water (0.20 mL). The tube was sealed, and the contents heated at 130° C. for 20 min using an Initiator microwave reactor (Personal Chemistry, Biotage AB, Inc., Upssala, Sweden). The reaction mixture was treated with water (40 mL) and extracted with EtOAc (75 mL). The organic layer was washed with brine, dried over MgSO4, filtered and concentrated. The crude material was purified by flash chromatography using an ISCO Combiflash Rf(12 g Thomson Single Step silica gel column; 30-100% EtOAc in hexanes) to afford N-(4-methoxybenzyl)-5-(3-(5-(methylsulfonyl)pyridin-2-yl)-1-tosyl-1H-indol-5-yl)-1,3,4-oxadiazol-2-amine (0.113 g, 0.179 mmol, 53.9% yield) as a brown amorphous solid. MS (ESI, pos. ion) m/z: 629.9 (M+H)+. 1H NMR (400 MHz, DMSO-d6) δ ppm 9.15 (d, J=2.2 Hz, 1H), 9.02 (d, J=1.4 Hz, 1H), 8.95 (s, 1H), 8.43 (s, 1H), 8.39 (d, J=2.3 Hz, 1H), 8.37 (s, 1H), 8.28-8.31 (m, 1H), 8.16 (d, J=8.8 Hz, 1H), 7.91 (d, J=1.6 Hz, 1H), 7.44 (d, J=8.6 Hz, 3H), 7.33 (m, J=8.6 Hz, 2H), 6.90 (m, J=8.8 Hz, 2H), 4.38 (d, J=5.9 Hz, 2H), 3.72 (s, 3H), 3.37 (s, 3H), 2.33 (s, 3H). A solution of N-(4-methoxybenzyl)-5-(3-(5-(methylsulfonyl)pyridin-2-yl)-1-tosyl-1H-indol-5-yl)-1,3,4-oxadiazol-2-amine (0.113 g, 0.179 mmol) in TFA (2.0 mL) was heated in an Initiator microwave reactor (Personal Chemistry, Biotage AB, Inc., Upssala, Sweden) at 100° C. for 20 min. The residual TFA was removed in vacuo. The residue was treated with 1 N NaOH (20 mL) and extracted with EtOAc (50 mL). The organic layer was washed with water (20 mL) then brine (20 mL), dried over MgSO4, filtered and concentrated to give 5-(3-(5-(methylsulfonyl)pyridin-2-yl)-1-tosyl-1H-indol-5-yl)-1,3,4-oxadiazol-2-amine as a beige solid. The material was used in the next step without purification, assuming the theoretical yield. MS (ESI, pos. ion) m/z: 509.9 (M+H)+. 5-(3-(5-(Methylsulfonyl)pyridin-2-yl)-1-tosyl-1H-indol-5-yl)-1,3,4-oxadiazol-2-amine (91 mg, 0.179 mmol) was weighed into a 5 mL glass microwave tube, and was treated with dioxane (1.5 mL) and 1 N NaOH (0.5 mL). The solution was heated in an Initiator microwave reactor (Personal Chemistry, Biotage AB, Inc., Upssala, Sweden) at 100° C. for 10 min. The reaction mixture was treated with water, extracted with EtOAc, and the organic layer was concentrated. The crude residue was dissolved in DMSO (2.5 mL) and purified by reverse phase using a Gilson automated platform (Silicycle Silichrome XT C18 column; 30×150 mm, 5 μm, 20-95% 0.1% TFA/CH3CN in 0.1% TFA/water by volume over 10 min), then dried in a Genevac Series II Evaporator affording 5-(3-(5-(methylsulfonyl)pyridin-2-yl)-1H-indol-5-yl)-1,3,4-oxadiazol-2-amine 2,2,2-trifluoroacetate (12.1 mg, 0.026 mmol, 14.43% yield) as an orange amorphous solid.). MS (ESI, pos. ion) m/z: 356.0 (M+H)+. 1H NMR (400 MHz, DMSO-d6) δ ppm 12.15 (br. s., 1H), 9.02 (s, 1H), 9.05 (s, 1H), 8.49 (d, J=2.5 Hz, 1H), 8.23 (dd, J=8.6, 2.3 Hz, 1H), 8.13 (d, J=8.6 Hz, 1H), 7.71 (d, J=8.4 Hz, 1H), 7.61 (d, J=8.6 Hz, 1H), 7.34 (br. s., 2H), 3.33 (s, 3H). 19F NMR (376 MHz, DMSO-d6) δ ppm −74.66 (br. s., 3F) TFA present.
