Boron trifluoride etherate → 1',2',3',4'-Tetrahydro-2'-hydroxy-5',8'-dimethoxyspiro[1,3-dithiolane-2,4'-naphthalene]-2'-carboxylic acid

HRID 462622Notes

Reaction equation

HRID 462622 reaction equation
C1COC2(C3[C:7](=[C:8]([O:15][CH3:16])[CH:9]=[CH:10][C:11]=3[O:13][CH3:14])[CH2:6][C:5]([OH:21])([C:17]([O:19]C)=[O:18])[CH2:4]2)O1.[CH:24]([SH:27])([SH:26])[CH3:25].B(F)(F)F.[CH3:32][CH2:33]OCC.[OH-].[Na+]>ClCCl.CO.C(OCC)C>[OH:21][C:5]1([C:17]([OH:19])=[O:18])[CH2:4][C:24]2([S:27][CH2:33][CH2:32][S:26]2)[C:25]2[C:7](=[C:8]([O:15][CH3:16])[CH:9]=[CH:10][C:11]=2[O:13][CH3:14])[CH2:6]1

Participants

8

Reactant 4

HCID 8000Boron trifluoride etherateHCID 14798Sodium HydroxideHCID 336451,1-EthanedithiolHCID 13264136Methyl rac-4,4-ethylenedioxy-1,2,3,4-tetrahydro-2-hydroxy-5,8-dimethoxynaphthalene-2-carboxylate

Product 1

HCID 132641391',2',3',4'-Tetrahydro-2'-hydroxy-5',8'-dimethoxyspiro[1,3-dithiolane-2,4'-naphthalene]-2'-carboxylic acidYield 66.5%

Reagents, catalysts & solvents 3

HCID 887MethanolSolventHCID 3283Diethyl EtherSolventHCID 6344DichloromethaneSolvent

Conditions

Temperature
0 °C

Procedure

10 g of methyl rac-4,4-ethylenedioxy-1,2,3,4-tetrahydro-2-hydroxy-5,8-dimethoxynaphthalene-2-carboxylate were dissolved in 30 ml of dichloromethane and the solution was cooled to 0° C. To the solution were added 4 ml of ethanedithiol followed by 4 ml of boron trifluoride etherate. The mixture was stirred at 0° C. for 15 minutes and then poured into 200 ml of diethyl ether. The organic layer was washed with three 50 ml portions of 5% sodium hydroxide solution and evaporated to give a yellow oil which was taken up in 200 ml of methanol. 100 ml of 5% sodium hydroxide solution were added and the resulting solution was stirred at room temperature for 1.5 hours. Most of the methanol was then evaporated, the residue was diluted with 250 ml of water and washed with three 100 ml portions of ether. The aqueous layer was acidified with hydrochloric acid and the precipitated oil was left to solidify. The product was collected by filtration, washed free from acid using water and dried. The crude acid was purified by suspension in 150 ml of ethyl acetate and heating under reflux for 30 minutes. The mixture was cooled and the product was collected by filtration after 24 hours. There were obtained 7.0 g (66.5%) of 1',2',3',4'-tetrahydro-2'-hydroxy-5',8'-dimethoxyspiro[1,3-dithiolane-2,4'-naphthalene]-2'-carboxylic acid in the form of colourless crystals of melting point 189°-189.5° C.

Workup

  1. washThe organic layer was washed with three 50 ml portions of 5% sodium hydroxide solution
  2. customevaporated
  3. customto give a yellow oil which
  4. stirringthe resulting solution was stirred at room temperature for 1.5 hours
  5. customMost of the methanol was then evaporated
  6. additionthe residue was diluted with 250 ml of water
  7. washwashed with three 100 ml portions of ether
  8. waitthe precipitated oil was left
  9. filtrationThe product was collected by filtration
  10. washwashed free from acid
  11. customdried
  12. customThe crude acid was purified by suspension in 150 ml of ethyl acetate
  13. temperatureheating
  14. temperatureunder reflux for 30 minutes
  15. temperatureThe mixture was cooled
  16. filtrationthe product was collected by filtration after 24 hours

Sources & evidence

ORD record
ord-2af9bce665464e11a53fc9970dd21e4d
Source dataset
uspto-grants-1985_05
Patent number
US04515969

Reaction notes

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