Reaction Steps
Prepared using General Procedure 14: To a stirred solution of (S)-5-(3-(1-amino-2,3-dihydro-1H-inden-4-yl)-1,2,4-oxadiazol-5-yl)-2-isopropoxybenzonitrile hydrochloride 50 (500 mg, 1.26 mmol) in DCM (5 mL) was added TEA (527 μL, 378 mmol). The reaction was cooled to 0° C. and acetyl chloride (135 μL, 1.89 mmol) was added. The reaction was stirred at room temperature for 18 h. The solvent was removed under reduced pressure. The residue was diluted with DCM (100 mL) and washed successively with saturated NH4Cl and NaHCO3. The organic layers were dried over MgSO4, filtered and concentrated to crude product. The crude product was recrystallized from hot ethanol (75 mL) to afford 420 mg (83%) of (S)—N-(4-(5-(3-cyano-4-isopropoxyphenyl)-1,2,4-oxadiazol-3-yl)-2,3-dihydro-1H-inden-1-yl)acetamide 139 as off-white crystals. LCMS-ESI (m/z) calculated for C23H22N4O3: 402.2; found 403.1 [M+H]+, tR=8.77 min (Method 2). Elemental Analysis determined for C23H22N4O3; C calculated=68.64%; found=68.54%. H calculated=5.51%; found=5.36%. N calculated=13.92%; found=13.85%. 1H NMR (400 MHz, DMSO) δ 8.58 (d, J=2.2 Hz, 1H), 8.47 (dd, J=9.0, 2.3 Hz, 1H), 8.39 (d, J=8.2 Hz, 1H) 8.08 (t, J=4.2 Hz, 1H), 7.62 (d, J=9.2 Hz, 1H), 7.57-7.47 (m, 2H), 5.45-5.39 (m, 1H), 5.20-4.97 (m, 1H), 3.51-3.42 (m, 1H), 3.25-3.00 (m, 1H), 2.55-2.50 (m, 1H), 1.96 (s, 3H), 1.94-1.87 (m, 1H), 1.45 (d, J=6.0 Hz, 6H). 13C NMR (101 MHz, CDCl3) δ 173.14, 169.85, 168.85, 162.79, 144.91, 143.26, 134.16, 133.89, 128.49, 127.40, 126.86, 123.29, 116.82, 115.29, 113.56, 103.97, 72.77, 54.56, 33.67, 31.70, 23.50, 21.75. Chiral HPLC: (S)—N-(4-(5-(3-cyano-4-isopropoxyphenyl)-1,2,4-oxadiazol-3-yl)-2,3-dihydro-1H-inden-1-yl)acetamide was eluted using 10% i-PrOH in hexanes plus 0.3% DEA: >99.9% ee, tR=15.09 min. (R)—N-(4-(5-(3-cyano-4-isopropoxyphenyl)-1,2,4-oxadiazol-3-yl)-2,3-dihydro-1H-inden-1-yl)acetamide 138 was prepared in an analogous fashion from (R)-5-(3-(1-amino-2,3-dihydro-1H-inden-4-yl)-1,2,4-oxadiazol-5-yl)-2-isopropoxybenzonitrile 49: >99.9% ee, tR for (R)-enantiomer=16.44 min.
