Piperonal → 5-(2,2-Dibromo-vinyl)-benzo[1,3]dioxole
Reaction equation
[CH:1]1[C:6]([CH:7]=O)=[CH:5][C:4]2[O:9][CH2:10][O:11][C:3]=2[CH:2]=1.C1(P(C2C=CC=CC=2)C2C=CC=CC=2)C=CC=CC=1.[C:31](Br)(Br)([Br:33])[Br:32]>C(Cl)Cl>[Br:32][C:31]([Br:33])=[CH:7][C:6]1[CH:1]=[CH:2][C:3]2[O:11][CH2:10][O:9][C:4]=2[CH:5]=1Participants
5
Reactant 3
Product 1
Reagents, catalysts & solvents 1
Procedure
To a solution of piperonal (4.5 g, 30 mmol) and triphenylphosphine (24 g, 90 mmol) in DCM (120 mL) in an ice-water bath was added a solution of carbontetrabromide (15 g, 45 mmol) over a 10 minutes period. After the addition completed, the ice-water bath was removed, the reaction stirred at ambient temperature for 2 h, and then quenched with saturated NaHCO3. Aqueous was separated, and extracted with dichloromethane (2 times). The organic layers were combined, dried over Na2SO4, filtered, and concentrated to give a redish colored residue, that was filtered through a short path silica gel plug, eluting with DCM/hexane (10% to 20%). Concentration of the filtrate gave the title compound (6.5 g, 74% yield) as a pale yellow liquid. 1H NMR (CDCl3) δ 7.36 (s, 1H), 7.18 (d, 1H, J=1.6 Hz), 6.95 (dd, 1H, J=1.5, 8.1 Hz), 6.79 (d, 1H, J=8.1 Hz), 5.99 (s, 2H).