Hydrazine hydrate (1:1) → 5-(3-Pyridyl)-2-pyrazoline

Under N2 atmosphere, hydrazine hydrate (3.65 mL, 2 equiv.) was added to a solution of 3-(3-pyridyl)acrolein (5.0 g) in t-BuOH (25 mL). The mixture was refluxed for 3 days, followed by evaporation under reduced pressure. The residue was taken up in DCM and washed with 5% aqueous NaHCO3. The organic phase was dried over Na2SO4 and evaporated under reduced pressure. This gave 5.0 g of a red oil, containing 74% of the anticipated product and 26% of the hydrazone intermediate that failed to undergo ring-closure. This material was used in subsequent steps without further purification. Characteristic pyrazoline signals in 1H NMR (400 MHz, CDCl3): δ 2.63-2.75 (m, 1H), 3.13-3.25 (m, 1H) 4.72-4.82 (m, 1H), 6.85 (br s, 1H).

1. temperatureThe mixture was refluxed for 3 days
2. customfollowed by evaporation under reduced pressure
3. washwashed with 5% aqueous NaHCO3
4. dry with materialThe organic phase was dried over Na2SO4
5. customevaporated under reduced pressure
6. additionThis gave 5.0 g of a red oil, containing 74% of the anticipated product and 26% of the hydrazone intermediate that
7. customThis material was used in subsequent steps without further purification

ORD record

ord-b2811bb47fe647e7a75ae671606e3709

Source dataset

uspto-grants-2010_06

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07728018B2