Hydrochloric Acid → Pyrazolo[1,5-a]pyridin-3-amine

HRID 1741573Notes

Reaction equation

HRID 1741573 reaction equation
Cl.[OH-].[Na+].Cl.[NH2:5][C:6]1[CH:7]=[N:8][N:9]2[CH:14]=[CH:13][CH:12]=[CH:11][C:10]=12.OC1C=CC(NC2C=NN3C=CC=CC=23)=CC=1>C(OCC)(=O)C.CO>[NH2:5][C:6]1[CH:7]=[N:8][N:9]2[CH:14]=[CH:13][CH:12]=[CH:11][C:10]=12

Participants

6

Reactant 4

HCID 313Hydrochloric Acid2×HCID 14798Sodium HydroxideHCID 19380140Pyrazolo[1,5-a]pyridin-3-amine hydrochlorideHCID 22402121Phenol, 4-(pyrazolo[1,5-a]pyridin-3-ylamino)-

Product 1

HCID 12068469Pyrazolo[1,5-a]pyridin-3-amine

Reagents, catalysts & solvents 1

HCID 21584119Ethylacetate methanolSolvent

Procedure

Pyrazolo[1,5-a]pyridine are dissolved in 30 ml. 6N hydrochloric acid, the solution is cooled to 0° C. and a solution of 6.9 g. sodium nitrite in 30 ml. water is slowly added dropwise thereto. After 1 hour, the nitrosation is complete. About 100 ml. water are added thereto, followed by repeated extraction with ethyl acetate. The organic phase is dried and evaporated. There are obtained 9.6 g. 3-nitrosopyrazolo[1,5-a]pyridine. 4.4.2 9 g. of the nitroso compound obtained according to 4.4.1 are introduced into a solution of 22 g. stannous chloride dihydrate in 180 ml. concentrated hydrochloric acid. The reaction mixture is stirred for 1 hour at ambient temperature and, for the completion of the reduction, mixed with 8 g. stannous chloride dihydrate in 30 ml. concentrated hydrochloric acid. The suspension is poured on to about 150 g. ice, adjusted with sodium hydroxide to pH 12 and quickly extracted with ethyl acetate. The ethyl acetate phase is dried and evaporated. The residue is dissolved in about 350 ml. diethyl ether and mixed with ethereal hydrochloric acid. The precipitate obtained is filtered of, washed with diethyl ether and dried. There are obtained 11.3 g. (100% of theory) 3-aminopyrazolo[1,5-a]pyridine hydrochloride; m.p. 228°-232° C. Rf (silica gel, ethyl acetate/methanol 9:1 v/v)=0.52. 4.4.3. The leuko coloured material 4-hydroxyphenyl-pyrazolo[1,5-a]pyridin-3-ylamine is obtained analogously to 4.3.2 and 4.3.3 with the use of 3-aminopyrazolo[1,5-a]pyridine as starting material. Rf (silica gel, ethyl acetate/diethyl ether 1:1 v/v)=0.68.

Workup

  1. additionare introduced into a solution of 22 g
  2. additionmixed with 8 g
  3. additionThe suspension is poured on to about 150 g
  4. extractionquickly extracted with ethyl acetate
  5. dry with materialThe ethyl acetate phase is dried
  6. customevaporated
  7. dissolutionThe residue is dissolved in about 350 ml
  8. additiondiethyl ether and mixed with ethereal hydrochloric acid
  9. customThe precipitate obtained
  10. filtrationis filtered of,
  11. washwashed with diethyl ether
  12. customdried
  13. customThere are obtained 11.3 g

Sources & evidence

ORD record
ord-c953f5c6a75342dea308797fe4c4f220
Source dataset
uspto-grants-1994_08
Patent number
US05334505

Reaction notes

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