1-Chloro-3-methyl-2-butene → 1,5-Dimethoxy-6-(3-methylbut-2-en-1-yl)cyclohexa-1,4-diene

Participants

Reaction Conditions

Reaction Steps

A portion of barium iodide dihydrate was dried over 12 h at 150° C. under 6 mmHg vacuum in a 250-mL round-bottom flask to yield activated barium iodide (8.38 g, 21.4 mmol, 1.1 equiv.), which was taken up in THF (125 mL). Meanwhile, a THF (50 mL) solution of 1 (2.73 g, 19.5 mmol, 1 equiv.) was cooled to −78° C. in a 500-mL round-bottom flask, and a pentane solution of tert-butyllithium (1.63 M, 13.1 mL, 21.4 mmol, 1.1 equiv.) was added over 5 min. After stirring the resulting clear yellow solution at −78° C. for 1 h, the THF slurry of activated barium iodide was transferred via cannula to this solution over 15 min. After stirring the resulting yellow-tan slurry an additional 30 min at −78° C., a THF (2 mL) solution of 3 (2.4 mL, 21.4 mmol, 1.1 equiv.) was added, and the slurry was allowed to warm over 2.25 h. The reaction was then quenched with water and extracted thrice with EtOAc. The organic extracts were combined, washed twice with brine, dried over Na2SO4, filtered, and concentrated in vacuo. The resulting clear oil was slowly loaded onto a SiO2 plug and eluted with 98:2 hexane:EtOAc. The eluent was concentrated in vacuo to afford 2.90 g (13.3 mmol, 68% yield) of 11 as a clear, colorless oil. TLC Rf 0.77 (9:1 hexane:EtOAc). 1H NMR (600 MHz; CDCl3): δ 4.99 (t, J=7.4 Hz, 1H), 4.68 (dd, J=4.6, 3.0 Hz, 2H), 3.53 (s, 6H), 2.94-2.91 (m, 1H), 2.78 (ddt, J=20.7, 6.0, 3.0 Hz, 1H), 2.72 (dq, J=20.7, 4.6 Hz, 1H), 2.41 (dd, J=7.4, 4.7 Hz, 2H), 1.64 (s, 3H), 1.55 (s, 3H). 13C NMR (125 MHz; CDCl3): δ 154.5, 132.8, 120.6, 91.9, 54.4, 41.3, 28.5, 26.1, 24.7, 17.8.

Provenance & Evidence