Ethyl bromopyruvate → 4-cyclopentyl-5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinoline-1-carboxylic acid ethyl ester

To a solution of 2-cyclopentyl-1,2,3,4-tetrahydroquinoline (4.0 g, 20 mmol) in tetrahydrofuran (15 ml) was added ethyl bromopyruvate (˜90% purity; 1.38 ml, 9.9 mmol) and the reaction stirred for 15 h. The resulting precipitate was filtered and washed with tetrahydrofuran (20 ml). The filtrate was evaporated in vacuo. The resulting residue was dissolved in tetrahydrofuran (10 ml) and 2-methoxyethanol (10 ml) and the solution added dropwise to a refluxing solution of magnesium (II) chloride (1.05 g, 11 mmol) in 2-methoxyethanol (10 ml). The reaction mixture was refluxed for 2 h and then a further portion of magnesium (II) chloride (1.05 g, 11 mmol) added and refluxing continued overnight. The reaction was cooled and the solvent removed in vacuo. The resulting brown oil was dissolved in dichloromethane (150 ml) and washed with 2 M HCl (50 ml), saturated potassium carbonate (50 ml) and brine (50 ml). The organics were dried (MgSO4), filtered and the solvent removed in vacuo. The resulting oil was purified by flash chromatography using 33-67% (v/v) dichloromethane in heptane to give 4-cyclopentyl-5,6-dihydro-4H-pyrrolo[3,2,1-ij]quinoline-1-carboxylic acid ethyl ester (1.45 g, 4.9 mmol).

1. filtrationThe resulting precipitate was filtered
2. washwashed with tetrahydrofuran (20 ml)
3. customThe filtrate was evaporated in vacuo
4. dissolutionThe resulting residue was dissolved in tetrahydrofuran (10 ml)
5. temperatureThe reaction mixture was refluxed for 2 h
6. temperaturerefluxing continued overnight
7. temperatureThe reaction was cooled
8. customthe solvent removed in vacuo
9. dissolutionThe resulting brown oil was dissolved in dichloromethane (150 ml)
10. washwashed with 2 M HCl (50 ml), saturated potassium carbonate (50 ml) and brine (50 ml)
11. dry with materialThe organics were dried (MgSO4)
12. filtrationfiltered
13. customthe solvent removed in vacuo
14. customThe resulting oil was purified by flash chromatography

ORD record

ord-88259a6a1ada4cdfb065d3ce7da4ed13

Source dataset

uspto-grants-2010_08

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07772227B2