Reaktion #362036

Reaktionsgleichung

2-chloro-3-pyridinecarboxylic acid, methyl ester

vinyltributyltin

2,6-ditertbutyl-4-methylphenol

N,N-dimethylformamide

vinyltributyltin

→

2-Ethenyl-3-pyridinecarboxylic acid, methyl ester

2-ethenyl-3-pyridinecarboxylic acid, methyl ester

Lösungsmittel

ethyl acetate

Reaktionsbedingungen

Aufarbeitung

1. 1
   TemperaturThe mixture is heated further at 40° C. for 61 hours
2. 2
   Einengenconcentrated at 60° C./5 mm
3. 3
   Sonstigeto leave a greenish oil that
4. 4
   Filtrationfiltered through a pad of silica gel (230-400 mesh)
5. 5
   workup.ADDITIONThe filtrate is diluted with additional ethyl acetate
6. 6
   Waschenthe organic phase is washed with water
7. 7
   Sonstigedried
8. 8
   Einengenconcentrated to an oil
9. 9
   workup.DISTILLATIONThe oil is distilled, with material
10. 10
    Sonstigecollected in the 80°-95° C./0.14 mm ranger

Vorschrift

2-Ethenyl-3-pyridinecarboxylic acid, methyl ester (12) is prepared as follows: a mixture of 19.7 g (115 mmol) of 2-chloro-3-pyridinecarboxylic acid, methyl ester (11), 38.3 g (120.8 mmol) of vinyltributyltin, 1.48 g (2.1 mmol) of bis(triphenylphosphine)palladium (II) chloride 100 mg of 2,6-ditertbutyl-4-methylphenol, and 250 mL of N,N-dimethylformamide is stirred at 55° C. for 7 hours, then treated with 1.63 g 15.1 mmol) of additional vinyltributyltin and 1 g of palladium catalyst. The mixture is heated further at 40° C. for 61 hours, then concentrated at 60° C./5 mm to leave a greenish oil that is dissolved in ethyl acetate and filtered through a pad of silica gel (230-400 mesh). The filtrate is diluted with additional ethyl acetate and the organic phase is washed with water, dried, and concentrated to an oil. The oil is distilled, with material collected in the 80°-95° C./0.14 mm ranger to leave 24.5 g of an oil that is ca. 75% product by GC. The oil is dissolved in dichloromethane:hexanes (1:1) and loaded onto an 8 x 15 cm of silica gel column (230-400 mesh). The column is eluted with the same solvent as above with 500 mL fractions collected. Product fractions are combined and carefully distilled at 65°-67° C./0.15 mm to leave 13.6 g of clear oil, >95% pure by GC, that is sufficiently pure to use directly in the next step.

Quelle