[F:1][C:2]1([F:16])[CH2:5][CH:4]([C:6]([O:8][CH2:9][C:10]2[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=2)=[O:7])[CH2:3]1.CI.[CH3:19][Si]([N-][Si](C)(C)C)(C)C.[K+]>C1COCC1>[F:1][C:2]1([F:16])[CH2:3][C:4]([CH3:19])([C:6]([O:8][CH2:9][C:10]2[CH:15]=[CH:14][CH:13]=[CH:12][CH:11]=2)=[O:7])[CH2:5]1To a solution of benzyl 3,3-difluorocyclobutanecarboxylate (2 g, 8.84 mmol) and MeI (2.202 mL, 35.4 mmol), in THF (15 mL) at −78° C. under a N2 atmosphere was added a solution of KHMDS (35.4 mL, 17.68 mmol, 0.5 M in toluene). The reaction mixture was then stirred at −78° C. for 6 h after which it was allowed to warm to RT and stir overnight. The reaction mass was then quenched with a saturated aq. solution of NH4Cl and extracted with diethyl ether (3×25 mL). The combined organic fractions were washed with water, dried over Na2SO4, filtered and concentrated under vacuum. The crude product was purified by silica gel chromatography (40 g REDISEP® column, eluting with 20% EtOAc in hexanes). Fractions containing the product were combined and evaporated to afford the Intermediate 296A as a pale yellow liquid (1.2 g, 56.5%). 1H NMR (400 MHz, chloroform-d) δ ppm 7.50-7.23 (m, 5H), 5.17 (s, 2H), 3.22-2.97 (m, 2H), 2.60-2.28 (m, 2H), 1.51 (s, 3H).
Wird geladen…
