Hydrogen Bromide → 6-Bromo-2-(3,4-dichlorophenyl)-2H-pyrano[2,3-b]pyridine

HRID 280191Notes

Reaction equation

HRID 280191 reaction equation
[Br:1][C:2]1[CH:3]=[C:4](/[CH:10]=[CH:11]/[C:12]([C:14]2[CH:19]=[CH:18][C:17]([Cl:20])=[C:16]([Cl:21])[CH:15]=2)=[O:13])[C:5](OC)=[N:6][CH:7]=1.[BH4-].[Na+].BrC1C=C(C=CC(C2C=CC(Cl)=C(Cl)C=2)O)C(OC)=NC=1.Br>O1CCCC1.C(O)C.C(O)(=O)C>[Br:1][C:2]1[CH:3]=[C:4]2[CH:10]=[CH:11][CH:12]([C:14]3[CH:19]=[CH:18][C:17]([Cl:20])=[C:16]([Cl:21])[CH:15]=3)[O:13][C:5]2=[N:6][CH:7]=1

Participants

8

Reactant 4

HCID 260Hydrogen BromideHCID 4311764Sodium borohydrideHCID 13567761HCID 13567761, compoundHCID 53640827HCID 53640827, compound

Product 1

HCID 5149096-Bromo-2-(3,4-dichlorophenyl)-2H-pyrano[2,3-b]pyridine

Reagents, catalysts & solvents 3

HCID 176Acetic AcidSolventHCID 702EthanolSolventHCID 8028TetrahydrofuranSolvent

Conditions

Temperature
85 °C

Procedure

To a stirred suspension of 30 g of (E)-3-(5-bromo-2-methoxy-3-pyridinyl)-1-(3,4-dichlorophenyl)-2-propen-1-one in 275 ml of tetrahydrofuran and 260 ml of absolute ethanol was added 6.0 g of sodium borohydride. After 1 hour under nitrogen, the reaction mixture was partitioned between aqueous 1N sodium hydroxide solution and ether. The ether layer was washed with aqueous saturated sodium chloride solution, dried over sodium sulfate and concentrated under reduced pressure to give a pale yellow oil which was crude α-[2-(5-bromo-2-methoxy-3-pyridinyl)ethenyl]-3,4-dichlorobenzenemethanol. To a stirred solution of 25.9 g of this crude alcohol in 400 ml of acetic acid under nitrogen there was added 25 ml of 48% aqueous hydrobromic acid. The mixture was heated to 85° C. for about 30 minutes then cooled rapidly to 23° C. in an ice bath, and partitioned between water and ether. The ether layer was washed several times with water and then successively with aqueous saturated sodium bicarbonate and sodium chloride solutions. It was then dried over sodium sulfate and the solvent evaporated under reduced pressure to give a pale yellow oil. Filtration through a layer of silica gel using chloroform as eluant gave 6-bromo-2-(3,4-dichlorophenyl)-2H-pyrano[2,3-b]pyridine as a pale yellow solid which exhibited the same characteristics as the material obtained in Example 8.

Workup

  1. customthe reaction mixture was partitioned between aqueous 1N sodium hydroxide solution and ether
  2. washThe ether layer was washed with aqueous saturated sodium chloride solution
  3. dry with materialdried over sodium sulfate
  4. concentrationconcentrated under reduced pressure
  5. customto give a pale yellow oil which
  6. temperaturethen cooled rapidly to 23° C. in an ice bath
  7. custompartitioned between water and ether
  8. washThe ether layer was washed several times with water
  9. dry with materialIt was then dried over sodium sulfate
  10. customthe solvent evaporated under reduced pressure
  11. customto give a pale yellow oil
  12. filtrationFiltration through a layer of silica gel

Sources & evidence

ORD record
ord-224b94c98eab4612abf82a45fe522673
Source dataset
uspto-grants-1986_05
Patent number
US04588733

Reaction notes

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