Potassium Hydroxide → (5-nitro-1H-indol-2-yl)methanol

To a solution of ethyl 5-nitro-1H-indole-2-carboxylate (9.8 g, 42.0 mmol) in methanol (300 mL) was added a solution of 2 M potassium hydroxide (31 mL, 63.0 mmol). The reaction mixture was heated at reflux for 2 h and then the hot solution was filtered, poured onto ice, and acidified. The resultant fine pale brown precipitate was collected by filtration and dried. The crude acid was dissolved in tetrahydrofuran (250 mL) and stirred with 1,1′-carbonyldiimidazole (10.2 g, 63.0 mmol) with gentle warming for 2 h. Water (100 mL) was added and then solid sodium borohydride (7.9 g, 0.21 mol) was added portionwise over 30 min, the reaction mixture was stirred for a further 40 min and then it was quenched with 1 M hydrochloric acid. The tetrahydrofuran was removed at reduced pressure and the residue was dissolved in ethyl acetate, washed, dried, and concentrated to give (5-nitro-1H-indol-2-yl)methanol (903). This material was used without purification in the next step.

1. temperatureThe reaction mixture was heated
2. temperatureat reflux for 2 h
3. filtrationthe hot solution was filtered
4. additionpoured onto ice
5. filtrationThe resultant fine pale brown precipitate was collected by filtration
6. customdried
7. dissolutionThe crude acid was dissolved in tetrahydrofuran (250 mL)
8. temperaturewith gentle warming for 2 h
9. customit was quenched with 1 M hydrochloric acid
10. customThe tetrahydrofuran was removed at reduced pressure
11. dissolutionthe residue was dissolved in ethyl acetate
12. washwashed
13. customdried
14. concentrationconcentrated

ORD record

ord-afddef511fda484ca8479efad51022a6

Source dataset

uspto-grants-2006_08

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07094798B1