Acetic Anhydride → TG 003

HRID 507331Notes

Reaction equation

HRID 507331 reaction equation
[I-].[CH2:2]([N+:4]1[C:8]2[CH:9]=[C:10]([O:13][CH3:14])[CH:11]=[CH:12][C:7]=2[S:6][C:5]=1[CH3:15])[CH3:3].[C:16](OC(=O)C)(=[O:18])[CH3:17].C(N(CC)CC)C>C(#N)C>[CH2:2]([N:4]1[C:8]2[CH:9]=[C:10]([O:13][CH3:14])[CH:11]=[CH:12][C:7]=2[S:6]/[C:5]/1=[CH:15]\[C:16](=[O:18])[CH3:17])[CH3:3]

Participants

5

Reactant 3

HCID 7918Acetic AnhydrideHCID 8471TriethylamineHCID 128234283-Ethyl-5-methoxy-2-methyl-1,3-benzothiazol-3-ium iodide

Product 1

HCID 1893668TG 003Yield 54.1%

Reagents, catalysts & solvents 1

HCID 6342AcetonitrileSolvent

Procedure

A series of benzothiazole compounds including TG003 were synthesized according to the procedures reported by Gupta et al. (27). In the case of TG003, a mixture of commercially available 5-methoxy-2-methylbenzothiazole (202 mg, 1.12 mmol) and ethyl iodide (2.70 ml, 33.7 mmol) was refluxed for 24.5 h. The precipitate was filtrated, washed with ethyl acetate (20 ml) on a funnel, and dried under reduced pressure to afford 3-ethyl-5-methoxy-2-methylbenzothiazolium iodide (270 mg, 0.805 mmol, 71.9%) as a pale green solid. To a suspension of 3-ethyl-5-methoxy-2-methylbenzothiazolium iodide (502 mg, 1.49 mmol) in acetonitrile (2.0 ml), acetic anhydride (330 μl, 3.49 mmol) and triethylamine (490 μl, 3.51 mmol) were successively added at room temperature. After refluxing for 2 h, the mixture was cooled to room temperature and concentrated under reduced pressure. Water (50 ml) was added to the residue, and the mixture was extracted with ethyl acetate (three times with 15 ml). The combined organic extracts were washed with brine (30 ml), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (18 g, CH2Cl2/ethyl acetate, 4:1) to afford (Z)-1-(3-ethyl-5-methoxy-2,3-dihydrobenzothiazol-2-ylidene) propan-2-one (TG003) (201 mg, 0.806 mmol, 54.1%) as a pale yellow solid.

Workup

  1. additionwere successively added at room temperature
  2. temperatureAfter refluxing for 2 h
  3. concentrationconcentrated under reduced pressure
  4. additionWater (50 ml) was added to the residue
  5. extractionthe mixture was extracted with ethyl acetate (three times with 15 ml)
  6. washThe combined organic extracts were washed with brine (30 ml)
  7. dry with materialdried over Na2SO4
  8. filtrationfiltered
  9. concentrationconcentrated under reduced pressure
  10. customThe residue was purified by silica gel column chromatography (18 g, CH2Cl2/ethyl acetate, 4:1)

Sources & evidence

ORD record
ord-b65cf58e2703477ea47374cb93254e3b
Source dataset
uspto-grants-2010_08
Patent number
US07786151B2

Reaction notes

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