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31st August 2011 @ 07:39
Product obtained in 89% yield.

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Scale up of PMY 1-5 from 20 mmol to 100 mmol scale.

Reaction Scheme PY14.png

Experiment start time: 1751 EST 31/08/11
4-fluoroaniline (10.4 mL, 110 mmol, 1.1 equiv.) and 2,5-hexanedione (11.7 mL, 100 mmol, 1 equiv.) were heated to 110 °C (oil bath temp.). After 15 hours, reaction was cooled to room temp. Stirring stopped. After 20 minutes, no precipitation. a couple of crystals of PMY 1-5a were added resulting in instant precipitation. EtOH (15 mL) was added and the solid dissolved by heating to 45 °C with stirring. After dissolution (about 5 mins.) the mixture was allowed to cool slowly, reaction precipitated and set solid. Dissolved again and a premixed solution of EtOH (30 mL) and 10% citric acid (15 mL) were added and the reaction allowed to cool. The resulting crystals were filtered and washed with water approx (200 mL) to obtain the product as tan crystals (14.98 g, 79%) after drying under vacuum. A second crop of brown crystals (1.89 g, 10%) was obtained from the mother liquor. Total of 89% yield from 2 crops.

Risk and Hazard Assessment:
As for Paal-Knorr Synthesis of 1-aryl-2,5-dimethyl Pyrrole Core (PMY 1-2), except reaction carried out neat and on a larger scale. 5 fold increase from PMY 1-5. Ice bath on stand by if required on initial mixing.

See also:
Scale-up (20 mmol) of Paal-Knorr Synthesis of 1-aryl-2,5-dimethyl Pyrrole Core (PMY 1-5)
Paal-Knorr Synthesis of 1-aryl-2,5-dimethyl Pyrrole Core (PMY 1-4)
Paal-Knorr Synthesis of 1-aryl-2,5-dimethyl Pyrrole Core (PMY 1-3)
Paal-Knorr Synthesis of 1-aryl-2,5-dimethyl Pyrrole Core (PMY 1-2)
Paal-Knorr Synthesis of 1-aryl-2,5-dimethyl Pyrrole Core (PMY 1-1)
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