5,7-DICHLOROPYRAZOLO[1,5-A]PYRIMIDINE Chemical Properties

Melting point:

68-71 °C(Solv: ethanol (64-17-5))

Density 

1.69±0.1 g/cm3(Predicted)

storage temp. 

under inert gas (nitrogen or Argon) at 2–8 °C

pka

-1.68±0.30(Predicted)

form 

Solid

color 

Off-white to yellow

InChI

InChI=1S/C6H3Cl2N3/c7-4-3-5(8)11-6(10-4)1-2-9-11/h1-3H

InChIKey

JMTFWCYVZOFHLR-UHFFFAOYSA-N

SMILES

C12=CC=NN1C(Cl)=CC(Cl)=N2

Safety Information

HS Code 

2933599590

5,7-DICHLOROPYRAZOLO[1,5-A]PYRIMIDINE Usage And Synthesis

Uses

5,7-Dichloropyrazolo[1,5-a]pyrimidine is a pharmaceutical intermediate compound that can be used in a palladium-catalysed pharmaceutical synthesis cross-coupling reaction. 2,4-Dichloroquinoline reacts with benzylzinc and phenylzinc reagents in the presence of catalytic quantities of palladium complexes to yield only α-substituted products.2,4-Dichloroquinolines have been found to react with benzylzinc and phenylzinc reagents in catalytic amounts of palladium compounds to produce only α-substituted products. LiCl was found to be an effective additive for γ-selective coupling reactions. These α- or γ-selective coupling conditions are applicable to the reaction of 5,7-Dichloropyrazolo[1,5-a]pyrimidine and biphenylmethyl zinc reagents in the synthesis of angiotensin II receptor antagonists. This regioselectivity should be generally applicable to other α,γ-dichloropyrazine systems^[1].

Synthesis

The general procedure for the synthesis of 5,7-dichloropyrazolo[1,5-a]pyrimidines from 7-hydroxy[1,5-a]pyrimidin-5(4H)-ones was as follows: trichlorophosphorus oxychloride (POCl3, 130 mL) was added to a reaction vial containing pyrazolo[1,5-a]pyrimidine-5,7-diol (10 g, 66 mmol). After the resulting suspension was cooled to 0°C, N,N-dimethylaniline (23 mL, 179 mmol) was slowly added. After the reaction mixture was warmed up to room temperature, the reaction was heated at 60°C for 16 h under the protection of nitrogen (N2). After completion of the reaction, the mixture was cooled to room temperature and concentrated to give a brown viscous liquid. This liquid was slowly poured into ice water and allowed to gradually warm to room temperature. Subsequently, the pH of the mixture was adjusted with saturated sodium bicarbonate (NaHCO3) solution to 8. The organic layer was extracted with dichloromethane (CH2Cl2, 4 x 50 mL), and the organic phases were combined and dried over anhydrous magnesium sulfate (MgSO4). The dried organic phase was concentrated under reduced pressure to give a brown liquid. Finally, the target product, 5,7-dichloropyrazolo[1,5-a]pyrimidine (10.7 g, 86% yield), was obtained as a white crystalline solid by fast column chromatography with the eluent ratio varied from 1:1 (v/v) dichloromethane:hexane gradient to 2:1 (v/v) dichloromethane:hexane. Mass spectrometry (MS) analysis showed m/z 189.36 [M + 1].

References

[1] TAKESHI SHIOTA; Teruo Y. Regioselective Reactions of Organozinc Reagents with 2,4-Dichloroquinoline and 5,7-Dichloropyrazolo[1,5-a]pyrimidine[J]. ACS Applied Electronic Materials, 1999. DOI:10.1021/jo981423a.

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