Ethylamine → 5-Ethyl-2-nitro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrazine

In a 100 mL round-bottomed flask, 1-(2-bromoethyl)-5-(bromomethyl)-3-nitro-1H-pyrazole (0.7 g, 2.24 mmol, Eq: 1.00) was combined with THF (25 ml) to give a light yellow solution. To this ethylamine (7.83 ml of 2M in THF, 15.7 mmol, Eq: 7) was added dropwise and the reaction mixture was stirred at ambient temperature for 12 hr. The reaction mixture was concentrated and the resulting solid was stirred with a mixture of EtOAc (250 mL) and 10% aqueous K2CO3 (200 mL). The layers were separated and aqueous layer was back extracted with EtOAc (2×100 mL). The combined organic layers were dried over MgSO4 and concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, 40 g, 1% to 4% MeOH in DCM). Fractions containing product were combined and concentrated to afford the desired product (427 mg). 1H NMR (300 MHz, CHLOROFORM-d) δ ppm 1.20 (t, J=7.18 Hz, 3 H) 2.68 (q, J=7.18 Hz, 2 H) 3.01 (t, J=5.48 Hz, 2 H) 3.72 (s, 2 H) 4.29 (t, J=5.67 Hz, 2 H) 6.64 (s, 1 H).

1. customto give a light yellow solution
2. concentrationThe reaction mixture was concentrated
3. stirringthe resulting solid was stirred with a mixture of EtOAc (250 mL) and 10% aqueous K2CO3 (200 mL)
4. customThe layers were separated
5. extractionaqueous layer was back extracted with EtOAc (2×100 mL)
6. dry with materialThe combined organic layers were dried over MgSO4
7. concentrationconcentrated in vacuo
8. customThe crude material was purified by flash chromatography (silica gel, 40 g, 1% to 4% MeOH in DCM)
9. additionFractions containing product
10. concentrationconcentrated

ORD record

ord-d8c4e60664fe493fa5abe6ae41c438c0

Source dataset

uspto-grants-2014_11

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08889682B2