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24th January 2013 @ 15:34

 

1-(4-Fluoro-phenyl)-2,5-dimethyl-1H-pyrrole (PT 1-1) (750 mg, 4 mmol) and sulfur trioxide•pyridine (600 mg, 4 mmol) were dissolved in toluene (6 mL) and heated to reflux for 16 hours. The reaction mixture was cooled to room temperature, then diluted with distilled water (20 mL) and extracted with dichloromethane (3 x 20 mL). The aqueous phase was evaporated to dryness to give a brown-white solid A (977 mg, NMR = pt-1-4A). The organic phase was evaporated to dryness to give only pure unreacted starting material (424 mg, 2.25 mmol, 56% recovery. NMR = PT-1-4B).

Analysis:

PT-1-4A NMR.png
 Sample A contained only mono-sulfonated pyrrole ring as evidenced by the desymmetrised pyrrole methyl groups and 3:3:1:4 distribution of integrals. The sample also contained 1.8 pyridiniums per product, indicating the product is present as a pyridinium salt and is probably also contaminated with pyridinium sulfate or unreacted Py•SO3. Lack of a third methyl peak at 2.3 indicated absence of toluene, which would otherwise complicate the aromatic region.

ESI-MS negative found m/z 268 indicating mono-substitution.

See also: Upscaled synthesis of sodium 1-(4-fluorophenyl)-2,5-dimethyl-1H-pyrrole-3-sulfonate (MD 6-3)

Conclusion: Further purification pending. Assuming no loss of material, PT-1-4A is 62% pure.

Linked Entries
Attached Files
PT-1-4 Risk Assessment.pdf
PT-1-4A NMR.png
PT-1-4 scheme.png
PT-1-4A NMR data.tar
PT-1-4B.pdf
PT-1-4A mass spec.jpg