Ethyl Acetate → (1R,2R)-1-methyl-2-(pent-4-en-1-yl)cyclopropanol

참여 물질

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To a solution of 1,6-heptadiene (19.65 g, 204 mmol), in THF (341 ml) was added EtOAc (6.67 ml, 68.1 mmol), and chlorotitanium triisopropoxide (68.1 ml, 68.1 mmol). Cyclohexylmagnesium chloride (2M, 153 ml, 306 mmol) was then added slowly over 2 hours. After an additional 1 hour of stirring at RT, the reaction mixture was filtered through CELITE. The filtrate was then concentrated in vacuo and purified on SiO2 (15% EtOAc/hexanes) to yield the title compound as a mixture of enantiomers. To a solution of the enantiomers (5.5 g, 39.2 mmol) in anhydrous DCM, at 0° C. and under N2, was added Et3N (10.9 mL, 78 mmol) and 4-nitrobenzoyl chloride (8.7 g, 47.1 mmol). The reaction was stirred for 2 hours, diluted with H2O (70 mL) and extracted with DCM (3×100 mL). The combined organic layer was dried over Na2SO4, filtered and concentrated in vacuo. The residue was purified on SiO2 (gradient elution, 0 to 50% EtOAc in hexane) to yield (1R,2R and 1S,2S)-1-methyl-2-(pent-4-en-1-yl)cyclopropyl 4-nitrobenzoate. The benzoate enantiomers (12 g, 41.5 mmol) were separated by chiral chromatography on an AD-H column, eluting with 10% CO2 in MeOH. The desired peak fractions were concentrated to give (1R,2R)-1-methyl-2-(pent-4-en-1-yl)cyclopropyl 4-nitrobenzoate. To a solution of (1R,2R)-1-methyl-2-(pent-4-en-1-yl)cyclopropyl 4-nitrobenzoate (4.87 g, 16.83 mmol) in MeOH (67 mL) was added K2CO3 (4.65 g, 33.7 mmol). The mixture was stirred for 1 hour, filtered, and concentrated in vacuo. The material was purified on SiO2 (gradient elution, 0-50% ether/hexanes) to give the title compound. 1H NMR (500 MHz) (CDCl3) δ 5.82 (m, 1H), 4.99 (m, 2H), 2.09 (m, 2H), 1.78 (s, 1H), 1.55 (m, 2H), 1.41 (s, 3H), 1.32 (m, 1H), 1.14 (m, 1H), 0.97 (m, 1H), 0.84 (m, 1H), 0.06 (m, 1H).

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