3,4-dihydro-2H-pyran → 4,5-Dichloro-2-(tetrahydro-pyran-2-yl)-2H-pyridazin-3-one

HRID 52781Notes

Reaction equation

HRID 52781 reaction equation
[Cl:1][C:2]1[C:7]([Cl:8])=[CH:6][N:5]=[N:4][C:3]=1[OH:9].[O:10]1[CH:15]=[CH:14][CH2:13][CH2:12][CH2:11]1.O.C1(C)C=CC(S(O)(=O)=O)=CC=1>O1CCCC1>[Cl:1][C:2]1[C:3](=[O:9])[N:4]([CH:11]2[CH2:12][CH2:13][CH2:14][CH2:15][O:10]2)[N:5]=[CH:6][C:7]=1[Cl:8]

Participants

5

Reactant 3

HCID 80803,4-dihydro-2H-pyran2×HCID 521998p-Toluenesulfonic acid monohydrateHCID 178518919HCID 178518919, compound

Product 1

HCID 107292624,5-Dichloro-2-(tetrahydro-pyran-2-yl)-2H-pyridazin-3-one

Reagents, catalysts & solvents 1

HCID 8028TetrahydrofuranSolvent

Procedure

4,5-Dichloro-3-hydroxypyridazine (3000 g, 18.18 moles), dihydropyran (1943 g, 23.08 mole), p-toluenesulfonic acid monohydrate (283 g, 1.49 moles) and 16 L of tetrahydrofuran were added to a 50 L round bottomed flask equipped with a heating mantle, reflux condenser and a mechanical stirrer. The mixture was stirred at reflux for 29 h. Additional dihydropyran was added at 6 h (1328 g, 15.79 mol) and at 21 h (780 g, 9.25 moles). The reaction mixture was allowed to cool to room temperature overnight. The mixture was concentrated in vacuo to an oily residue. The residue was taken up in 16 L of ethyl acetate and washed with 2N NaOH (2×6 L). The organic solution was dried (MgSO4) and concentrated in vacuo to give 4,5-dichloro-2-(tetrahydro-2H-pyran-2-yl)-3(2H)-pyridazinone which was a black oily solid which was used without further purification in the next step. The product was purified by filtration through silica gel with ethyl acetate followed by evaporation and recrystallization from ethyl acetate/cyclohexane to give a white solid, mp=74°-76° C.

Workup

  1. customequipped with a heating mantle
  2. temperaturereflux condenser and a mechanical stirrer
  3. temperatureat reflux for 29 h
  4. concentrationThe mixture was concentrated in vacuo to an oily residue
  5. washwashed with 2N NaOH (2×6 L)
  6. dry with materialThe organic solution was dried (MgSO4)
  7. concentrationconcentrated in vacuo

Sources & evidence

ORD record
ord-1a50f12753d547728d54174444331cc9
Source dataset
uspto-grants-1997_04
Patent number
US05616789

Reaction notes

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