Reaktion #3196

Reaktionsgleichung

potassium t-butoxide

methyl 2-amino-4-chlorobenzoate

dimethyl acetylenedicarboxylate

dimethyl acetylenedicarboxylate

→

dimethyl 7-chloro-4-hydroxyquinoline-2,3-dicarboxylate

Ausbeute 28.9%

Lösungsmittel

t-butanol

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturwas refluxed for 7 hr under a nitrogen atmosphere
2. 2
   Temperaturrefluxing another 2.5 hr
3. 3
   SonstigeA precipitate formed
4. 4
   Temperaturthe resulting mixture was refluxed for 1.5 hr
5. 5
   TemperaturThe mixture was cooled to room temperature
6. 6
   Filtrationfiltered
7. 7
   Sonstigeto separate the solids, which
8. 8
   Waschenwere washed with t-butanol and ether
9. 9
   workup.DISSOLUTIONThe solids were dissolved in water
10. 10
    Sonstigeto form a precipitate
11. 11
    ExtraktionThe resulting mixture was extracted with methylene chloride
12. 12
    Waschenthe combined extracts were washed with brine and water
13. 13
    Trocknendried (MgSO4)
14. 14
    Filtrationfiltered
15. 15
    Einengenconcentrated
16. 16
    Sonstigeto give a green solid
17. 17
    SonstigeRecrystallization of this material from methanol

Vorschrift

A stirred mixture of methyl 2-amino-4-chlorobenzoate (2.50 g, 13.5 mM) and dimethyl acetylenedicarboxylate (2.05 g, 14.4 mM) in t-butanol (22 mL) was refluxed for 7 hr under a nitrogen atmosphere. After adding additional dimethyl acetylenedicarboxylate (1.16 g, 8.13 mM) and refluxing another 2.5 hr, the reaction mixture was allowed to cool to room temperature and potassium t-butoxide (1.56 g, 13.9 mM) was added in one portion. A precipitate formed and the resulting mixture was refluxed for 1.5 hr. The mixture was cooled to room temperature and filtered to separate the solids, which were washed with t-butanol and ether. The solids were dissolved in water and acidified with 1N sulfuric acid to form a precipitate. The resulting mixture was extracted with methylene chloride and the combined extracts were washed with brine and water, dried (MgSO4), filtered and concentrated to give a green solid. Recrystallization of this material from methanol provided dimethyl 7-chloro-4-hydroxyquinoline-2,3-dicarboxylate (1.15 g, 28.9%) as an off-white solid, mp 232-233° C.; MS(CI): 296 (M+H).

Quelle