Triethylamine → 3-Chloro-5-methyl-1,2-benzoxazole

Participants

Reaction Steps

3-Hydroxy-5-methyl-1,2-benzisoxazole (15.0 g, 100.6 mmol; preparation: Australian Journal of Chemistry (1977), 30(8), 1847-50) were suspended in triethylamine (15.4 ml, 110.6 mmol), and phosphorus oxytrichloride (37.0 g, 22.5 ml, 241.4 mmol) was added dropwise with cooling to this mixture at room temperature. Since stirring of the reaction mixture became almost impossible after about half the amount of phosphorus oxytrichloride had been added dropwise, the temperature was raised to 50° C. After dropwise addition of the total amount of phosphorus oxytrichloride, the reaction mixture was heated at 130° C. for 5 h, after which the reaction was complete according to TLC. After cooling, the mixture was slowly added dropwise to water (200 ml) while cooling, the aqueous phase was extracted 3 times with MtB ether, the organic phases were washed with water, dried over magnesium sulfate and concentrated in vacuo. This resulted in 14.6 g of 3-chloro-5-methyl-1,2-benzisoxazole (yield: 87%) as viscous oil which solidified overnight. MS (MSD) m/z 168 [M+H+].

Provenance & Evidence