2,5-Dimethoxybenzaldehyde → 1,3-Dioxolane

Participants

Reaction Conditions

Reaction Steps

2-[(3E,5E,9Z)-10-(2,5-Dimethoxyphenyl)-3-methyl-deca-3,5,9-trienyl]-[1,3]dioxolane was synthesized as follows: to a −78° C. solution of (4E,6E)-(9-[1,3]dioxolan-2-yl-7-methyl-nona-4,6-dienyl)triphenylphosphonium iodide (500 mg, 0.840 mmol) in 5 mL of THF was added dropwise 0.5 mL of a 2 M solution of NaHMDS in THF. After 40 minutes at −78° C., a solution of 2,5-dimethoxybenzaldehyde (167 mg, 1.01 mmol) in 1 mL of THF was added dropwise. The reaction was warmed to 0° C. over 2 hours, brine was added, and the mixture was extracted with Et2O. The combined organic extracts were washed with a saturated solution of NaHCO3, dried (Na2SO4) and concentrated. Chromatography on SiO2 (hexanes/EtOAc 10:1) gave 162 mg (0.453 mmol, 54%) of oily 2-[(3E,5E,9Z)-10-(2,5-dimethoxphenyl))-3-methyl-deca-3,5,9-trienyl]-[1,3]dioxolane as a 5:1 mixture of (9Z):(9E) isomers: 1H NMR δ6.82-6.70 (m, 3H), 6.51 (d, 1H, J=11.5 Hz), 6.25 (dd, 1H, J=15.2, 11.0 Hz), 5.82 (d, 1H, J=10.6 Hz), 5.78-5.69 (m, 1H), 5.60 (dt, 1H, J=14.1, 6.8 Hz), 4.85 (t, 1H, 4.7 Hz), 3.97-3.82 (m, 4H), 3.78 (s, 3H), 3.76 (s, 3H), 2.39-2.31 (m, 2H), 2.30-2.21 (m, 2H), 2.20-2.10 (m, 2H). 181-1.72 (m, 2H), 1.73 (s, 3H).

Provenance & Evidence