Triethylamine → 2-(2-Phenyl-4-pyridyl)-4H-1,3-benzothiazine-4-one

Participants

Reaction Steps

2-Chloro-4-cyanopyridine (0.40 g, 2.9 mmol), phenylboric acid (0.53 g, 4.3 mmol) and potassium carbonate (1.0 g, 7.2 mmol) were dissolved in toluene-ethanol-water (4:1:1, 30 ml), and the mixture was deairated under reduced pressure for 15 minutes. Tetrakis(triphenylphosphine)palladium (0.17 g, 0.14 mmol) was added to the mixture under nitrogen atmosphere, and the mixture was refluxed for 21 hrs. The reaction mixture was combined with ethyl acetate-water. The organic layer was washed with saturated brine and dried over an hydrous magnesium sulfate. The solvent was evaporated under reduced pressure to give crude 2-phenylisonicotinenitrile. Methyl thiosalicylate (1.10 g, 6.5 mmol) and 2-phenylisonicotinenitrile (0.50 g, 2.8 mmol) was dissolved in toluene (2.0 ml), and triethylamine (1.1 ml, 7.9 mmol) was added thereto. The reaction mixture was refluxed for 18 hrs, cooled at room temperature to give precipitated crystals, which were collected by filtration. The filtrate was concentrated, subjected to a silica gel (50 g) column chromatography and eluted with hexane-ethyl acetate (2:1, v/v) to give crystals, which were combined with the previously obtained crystals and recrystallized from ethanol to give the titled compound (0.34 g, 27%) as white crystals.

Provenance & Evidence