2 Methods of preparation of 3-(1H-tetrazol-5-yl)oxanilic acid:
1. 5.0 g of 3-(1H-tetrazol-5-yl)aniline was dissolved in 25 ml of N,Ndimethylformamide,
followed by adding 5.68 g of triethylamine. Then, 5.64 g
of ether oxalyl chloride was dropwise added to the solution while cooling in ice
water. After completion of the dropwise addition, the reaction temperature
was slowly raised up to room temperature and the reaction was continued for
15 h. After the reaction was completed, the reaction mixture was poured into
100 ml of ice water and crystals separated out from the solution was filtered
off to obtain 8.3 g of ethyl 3-(1H-tetrazol-5-yl)oxanilate (yield 94.1%),
melting point 192°-l93°C (recrystallized from acetone/n-hexane).
The ethyl 3-(1H-tetrazol-5-yl)oxanilate (5.0 g), was dissolved in 35 ml of
ethanol and 100 ml of 0.5 N sodium hydroxide was dropwise added thereto
under water cooling. After the dropwise addition, the reaction temperature
was slowly raised up to room temperature and under such condition, the
reaction was carried out for 3 h. This solution was dropwise added to 70 ml of
4 N hydrochloric acid at room temperature. Thereafter, the solution was
stirred for 1 h and crystals separated out from the solution was filtered off.
The resultant crystals were washed with water and 3.9 g of 3-(1H-tetrazol-5-
yl)oxanilic acid was recovered (yield 87.4%), melting point 241°-243°C (dec.
recrystallized from isopropyl).
2. Oxalyl chloride (12.0 g) was dissolved in 50 ml of anhydrous
dimethoxyethane. To this solution a solution of 3-(1H-tetrazol-5-yl)aniline (5.0
g) in 250 ml of anhydrous dimethoxyethane was dropwise added over 3 h at
room temperature while stirring. Insolubles were removed by filtering the
solution, then 50 ml of water was gradually added to the reaction mixture
under ice cooling and stirring was continued for 1 h at room temperature.
Then, 500 ml of ethyl acetate was added thereto to carry out extraction, the
extract was washed with water, dried over anhydrous sodium sulfate and then
the solvent was distilled off to obtain 5.4 g of the 3-(1H-tetrazol-5- yl)oxanilic
acid (yield 74.8%), melting point 241°-243°C (dec. recrystallized from
isopropyl).
