Hydrochloric Acid → 1-Tetrazolylacetic acid

Temperature

70 °C

The crude 5-(isobutoxycarbonyl)-1H-tetrazole-1-acetic acid, ethyl ester prepared above was treated with 37.5 ml. (0.45 moles) of concentrated hydrochloric acid and 37.5 ml. of water in a 250 ml. 3-neck round bottom flask. The reaction mixture was heated to reflux, and the alcohols liberated as by-products of the reaction were allowed to distill out and carbon dioxide was permitted to evolve. Water was added as required during the reaction to maintain the volume in the flask at approximately 110 ml. When the distillation of the alcohols had ended, the mixture was treated with approximately 1 ml. of nitric acid to decolorize the solution. The solution was then cooled to approximately 70° C. and treated with charcoal. The solution was stirred for approximately 20 minutes and filtered hot into a clean 250 ml. 3-neck round bottom flask, washing with a minimum of water. The volume of the solution was reduced to approximately 120 ml. by distillation in vacuo and the mixture cooled. The precipitated solid was collected by filtration to afford 46.48 grams (98.1% pure) of 1H-tetrazole-1-acetic acid (m.p. 128.5°-130° C.). The overall yield of the synthesis from ethyl chloroacetate was 80.6% in the first cycle. When the 1H-tetrazole-1-acetic acid mother liquor was used as the solvent for the hydrolysis reaction in subsequent batches, the average yield of product over 9 cycles was 93.1%, with an average assay of 98.5% purity. The mother liquor was discarded after 9 cycles due to the salt accumulation.

1. additionabove was treated with 37.5 ml
2. temperatureThe reaction mixture was heated
3. temperatureto reflux
4. distillationto distill out
5. additionWater was added
6. customas required during the reaction
7. temperatureto maintain the volume in the flask at approximately 110 ml
8. distillationWhen the distillation of the alcohols
9. additionthe mixture was treated with approximately 1 ml
10. additiontreated with charcoal
11. filtrationfiltered hot into a clean 250 ml
12. wash3-neck round bottom flask, washing with a minimum of water
13. distillationby distillation in vacuo
14. temperaturethe mixture cooled
15. filtrationThe precipitated solid was collected by filtration

ORD record

ord-03b4d0ccf7c144e8ba2d2acb62bbca50

Source dataset

uspto-grants-1985_09

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04539422