Diethyl Ether → 3-(1-propenyl)-1,5-dihydro-3H-2,4-benzodioxepine

Participants

Reaction Steps

Crude 3-methoxy-1,5-dihydro-3H-2,4 benzodioxepine (361 mg, 2.2 mmol) was dissolved in dry DME (2 mL) p-toluenesulfonic acid (95.2 mg, 0.5 mmol) and chrotonaldehyde (0.166 mL, 2 mmol) were added. The mixture was stirred at rt. for 2 h. Ether (10 mL) was added and the organic layer washed with a saturated solution of NaHCO3 and water, then dried (Na2SO2). After removed the solvent the crude was purified by cc using AcOEt/Hexane (1:1) as eluent. 3-(1-Propenyl)-1,5-dihydro-3H-2,4-benzodioxepine 3 was obtained as an oil (175 mg, 46%). 1HNMR (CDCl3): δ 7.39-7.12 (m, 4H), 5.98 (dqd, J=15.5, 6.5 and 1.0 Hz, 1H), 5.53 (ddq, J=15.5, 4.7 and 1.4 Hz, 1H), 5.32 (dd, J=4.6 and 0.8 Hz, 1H), 4.94 (d, J=14.2 Hz, 2H), 4.86 (d, J=14.2 Hz, 2H), 1.74 (dqd, J=6.4, 1.5 and 0.8 Hz, h.). 13CNMR(CDCl3): δ 5 138.8, 130.1, 127.8, 127.1, 127.0, 104.7, 70.0, 17.6.

Provenance & Evidence