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In a 100 mL two-neck round-bottomed flask fitted with a reflux condenser, were placed 5-nitrobenzocyclobutenone (2.50 g, 15.34 mmol), iron powder (2.50 g) and aqueous ethanol (50%, 25 mL). The mixture was heated to gentle boiling. With a good stirring, concentrated hydrochloric acid (36%, 0.15 mL) in aqueous ethanol (50%, 5 mL) was added slowly. Stirring and reflux stopped until TLC showed no more starting compound. It usually took 5-60 min. After cooling to room temperature, the reaction solution was treated with sodium carbonate powders to pH 8-9. The insoluble solids were removed by filtration and further washed with methanol. The filtrate and washing solution were combined and concentrated by distillation at 50° C. under vacuum. Upon cooling, the pure product crystallized out and then collected by suction filtration: 1.88 g (92.4%); mp 92°-93° C.; IR (KBr) 1620, 1744, 3362, 3466 cm-1 ; 1H NMR (200 MHz, CDCl3) 3.85 (s, 2H), 3.86 (s, 2H), 6.64 (s, 1H), 6.88 (d, 1H), 7.33 (d, 1H); MS (EI, m/e, relative intensity %) 133 (M+., 31.2), 105 (M+. -CO, 100) .

1. customIn a 100 mL two-neck round-bottomed flask fitted with a reflux condenser
2. temperatureThe mixture was heated to gentle boiling
3. temperaturereflux
4. customIt usually took 5-60 min
5. customThe insoluble solids were removed by filtration
6. washfurther washed with methanol
7. washThe filtrate and washing solution
8. concentrationconcentrated by distillation at 50° C. under vacuum
9. temperatureUpon cooling
10. customthe pure product crystallized out
11. filtrationcollected by suction filtration