Piperonal → 5-(2,2-Dibromo-vinyl)-benzo[1,3]dioxole

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).

1. additionAfter the addition
2. customthe ice-water bath was removed
3. customquenched with saturated NaHCO3
4. customAqueous was separated
5. extractionextracted with dichloromethane (2 times)
6. dry with materialdried over Na2SO4
7. filtrationfiltered
8. concentrationconcentrated
9. customto give a redish colored residue, that
10. filtrationwas filtered through a short path silica gel plug
11. washeluting with DCM/hexane (10% to 20%)

ORD record

ord-b1d78607255e4db591db91c514e39db9

Source dataset

uspto-grants-2005_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06855722B2