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11th July 2012 @ 04:32
Product synthesised (pending mass spec) in good yield, although mixed with SM and by-product. It should be possible to easily remove succinimide by-product by washing.

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Bromination of 4-fluorophenylpyrrole PMY 1-6 using NBS in THF. Repeat of condition used for PMY 52-1.

PMY52-1.png

Reaction Start Time: 15.00 11/07/12
PMY 1-6 (1.00 g, 5.3 mmol, 1 equiv.) was dissolved in THF and cooled to ca. -15 °C. NBS (0.94 g, 5.3 mmol, 1 equiv.) was added portionwise over 20 minutes. The reaction was allowed to slowly warm. At 1 hr, TLC shows red stain, mixed spot shows hints of orange; reaction probably not complete. After 2 hours, temperature now 5 °C. Reaction not complete. TLC vanillin stain (unheated) shows presence of SM [product on PMY 52-1 did not stain immediately on dipping, showed disappearance before heating]. 1H NMR consistent with product observed in PMY 52-1 and a small amount of SM (1:0.09). Brown oil, crystallises slowly (1.41 g, 100% of theory; 92% calculated from NMR). NMR sample degraded overnight. Fresh sample 13C NMR consistent with expected product, a small amount of SM and residual succinimide at 29.59 ppm (7.77 ppm 1H).

300 MHz: Product:SM:succinimide 1:0.08:0.08; approx 86% product.

TLC (5% EtOAc/hexane) visualised with UV and vanillin:
TLC 1 hour
TLC 2 hrs vanillin unheated


NMR:
1H NMR 200 MHz
1H, 13C NMR


Mass Spec:
HRMS (APCI) found 268.01341 [M+H], C12H1279BrFN requires 268.01317.

See also:
Bromination of aryl pyrrole PMY 1-6 using NBS (PMY 52-1)
Bromination of aryl pyrrole PMY 1-6 using NBS (PMY 52-2)
Scale-up (100 mmol) of Paal-Knorr Synthesis of 1-aryl-2,5-dimethyl Pyrrole Core (PMY 1-6)

Risk and Hazard Assessment:
See: Bromination of aryl pyrrole PMY 1-6 using NBS (PMY 52-1)
Attached Files
TLC 1 hour
TLC 2 hrs vanillin unheated
1H NMR 200 MHz
1H, 13C NMR