Iodine → 2-Methyl-3-penten-1-ol

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Preparation of (E)-N-(3-Ethyl-3-methyl-2-propenyl)-morpholine (17): 2-Methyl-3-penten-1-ol was prepared using a modification of the procedure outlined by Corey and coworkers (Corey et al. (1973)Tetrahedron Lett. 18:1611). To a solution of 2-pentyn-1-ol (2.5 mL, 27 mmol) in THF (100 mL) was added Red-Al (8.1 mL of a 3.5 M solution in toluene, 28 mmol). The resulting solution was warmed to reflux for 3.5 h and then cooled to −78° C., before a solution of iodine (20.5 g, 81.0 mmol) in THF (50 mL) was added dropwise by syringe. The resulting solution was then allowed to warn to rt before Et2O (200 mL) was added, and the reaction mixture washed with 5% Na2SO4 (3×200 mL), dried (Na2SO4), and concentrated to afford 3-iodo-2-penten-1-ol as a crude product that was used without further purification. To a solution of copper(I)iodide (20.1 g, 0.11 mol) and methyl lithium (162 mL of a 1.3 M solution in Et2O, 0.21 mol) in Et2O (60 mL) at 0° C. was added a solution of the crude 3-iodo-2-penten-1-ol. The reaction mixture was stirred at 0° C. for 62 h and then washed with sat. aq. NH4Cl (3×200 mL), dried (Na2SO4), and concentrated to provide 2-methyl-3-penten-1-ol in 91% yield (2.1 g, 21 mmol) as a pure oil by 1H NMR analysis. Spectroscopic data of this material were in complete agreement with reported literature values. Normant et al. (1973) Tetrahedron Lett. 26:2407.

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