[I:1]N1C(=O)CCC1=O.[CH:9]1([C:13]2[CH:22]=[CH:21][C:16]([C:17]([O:19][CH3:20])=[O:18])=[C:15]([CH3:23])[CH:14]=2)[CH2:12][CH2:11][CH2:10]1.CO>S(=O)(=O)(O)O>[CH:9]1([C:13]2[C:22]([I:1])=[CH:21][C:16]([C:17]([O:19][CH3:20])=[O:18])=[C:15]([CH3:23])[CH:14]=2)[CH2:10][CH2:11][CH2:12]1N-Iodosuccinimide (3.52 g, 15.6 mmol) was added portion-wise to a solution of methyl 4-cyclobutyl-2-methylbenzoate (compound 6.2, 3.2 g, 15.6 mmol) in concentrated sulfuric acid (25 mL) at 0° C. The mixture was stirred at 0° C. for 30 min and at RT for 2 hours, upon where the mixture turned very thick. The mixture was again cooled to 0° C. and MeOH (30 mL) was slowly and carefully added. The mixture was heated at 60° C. for 2 hours. After cooling to room temperature, the solvent was removed under reduced pressure and the residue was poured onto ice water (100 mL). The mixture was extracted with EtOAc (2×). The combined organic layers were washed with brine, then aqueous 1M NaHCO3 (note-significant gas evolution), dried (Na2SO4), filtered, and concentrated. The residue was purified by silica gel column chromatography (hexanes:EtOAc 30:1 to 20:1) to yield the title compound as a light yellow oil (4.17 g, 81%). 1H NMR (400 MHz, CDCl3) δ 8.33 (s, 1H), 7.14 (s, 1H), 3.87 (s, 3H), 3.67-3.54 (m, 1H), 2.57 (s, 3H), 2.51-2.40 (m, 2H), 2.14-1.97 (m, 3H), 1.82-1.79 (m, 1H).
Wird geladen…
