Phthalic Anhydride → 6,7-Methylenedioxy-3-nitrochromene

Participants

Reaction Steps

Aldehyde (2a) (6 g, 36.14 mmol) was dissolved in 300 ml of CH2Cl2 along with 3.1 ml of dibutylamine (18.16 mmol) and 10.72 g of phthalic anhydride in a two necked flask equipped with a Dean-Stark trap, a condenser and a dropping funnel. Nitroethanol (7 ml 97.69 mmol) was added dropwise over a period of 18 hours, while the solution was stirred at reflux. After addition, the reaction was stirred for an additional 24 hrs. The flask was then cooled to room temperature, filtered and the solution extracted with 2 M NaOH (300 ml×3) and brine (100 ml), then dried over MgSO4. The solvent was then evaporated to leave a concentrated solution which was passed through a short column of silica to remove dark polar impurities. The isolated material was recrystallized from methanol to give 4.89 g (61% yield) of the title compounds as red needles: mp 139° C.; 1H-NMR (CDCl3) δ 5.20 (s, 2, ArOCH2), 6.02 (s, 2, OCH2O), 6.49 (s, 1, ArH), 6.69 (s, 1, ArH), 7.75 (s, 1, ArCH).

Provenance & Evidence