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14th November 2013 @ 18:11

reaction scheme

1-(4-methylphenyl)-2,5-dimethylpyrrole: p-Toluidine (0.562 g, 5.245 mmol) was combined with 2,5-hexanedione (0.530 mL, 4.518 mmol) and heated to 130º C overnight. The solution was allowed to cool and was then dissolved in ether (20 mL). Citric acid (20 mL, 10%) was added to the reaction. The bottom layer was extracted with ether (20 mL) and organic layers were combined. Organic layer was washed with H2O (15 mL) and the bottom aqueous layer was removed. Saturated NaCl (15 mL) was added to the solution and the bottom aqueous layer was separated. The organic layer was dried (MgSO4) and filtered. Filtered product was concentrated under reduced pressure. A stream of air was applied to the product, and the product was scraped until a solid formed. Recrystallization (ethanol) and vacuum filtration afforded a light brown solid (0.3243 g, 39%): Melting point 44.5º C - 45.5º C; FTIR 3033.95, 2987.29, 2919.29, 1913.44, 1625.31, 1582.40; 1H NMR (400 MHz, CDCl3) δ 7.247 (d, J= 8 Hz, 2H), 7.086 (d, J= 8 Hz, 2H), 5,884 (s, 2H), 2.415 (s, 3H), 2.019 (s, 6H).

 

1-(4-methylphenyl)-2,5-dimethylpyrrole-3-carboxaldehyde: Dimethylformamide (1 mL, 12.97 mmol) was put under a nitrogen atmosphere. Phosphoryl chloride (0.118 mL, 1.27 mmol) was added, and the reaction was put in an ice bath and stirred for 25 minutes; the solution turned bright red during stirring. Product pyrrole (0.2 g, 1.08 mmol) was dissolved in DMF (1 mL, 12.97 mmol) and added dropwise to the reaction over five minutes. The reaction was warmed to room temperature. TLC was performed to monitor the reaction by taking a drop of reaction product and adding 3:1 hexanes, NaOH (0.5 mL, 26.63 mmol), and ether (0.5 mL, 4.81 mmol), and then performing TLC on the top extracted layer. Product was poured over ice (20 mL), and NaOH (10%) was added to adjust the pH to 6 and then to 11. The product was stirred for 45 minutes while pH was continuously monitored. The development of crystals was observed. The product was filtered and dried for 10 minutes. Product crystals were dissolved in MeCN (3 mL), swirled, and heated until dissolved. Recrystallization and vacuum filtration yielded a dark brown crystalline solid (0.129 g, 56): Melting point 109.2º C - 111.0º C; FTIR 3333.79, 2920.23, 2738.18, 1648.91, 1532.12, 1514.79; 1H NMR (400 MHz, CDCl3) δ 9.868 (s, 1H), 7.297 (m, 2H), 7.075 (m, 2H), 6.3725 (d, 1H), 2.443 (s, 3H), 2.270 (s, 3H), 1.979 (s, 3H).

Final Product: (Z)-2-((3-phenyl)imino)thiazolidin-4-one (0.1021 g, 0.49 mmol) was dissolved in EtOH (2 ml), and piperidine (0.08 mL, 0.809 mmol) followed by product pyrrole (0.1039 g, 0.488 mmol) were added to the dissolved solution. Solution was incubated for 90 minutes (60º C); crystallization was observed. Product underwent vacuum filtration and was washed with EtOH (4 mL). Final product was a tan crystalline powder (0.0514 g, 27%): Decomposition temperature: 240.3º C; FTIR 3041.29, 2943.76, 2917.61, 2738.94, 1701.25, 1636.69, 1585.99. 1H NMR (400 MHz, CDCl3) δ 7.733, (s, 1H), 7.414 (t, J= 7.8 Hz, 2H), 7.20 (m, 5-6H), 7.041 (d, J= 8 Hz, 2H), 6.114 (s, 1H), 2.429 (s, 3H), 2.130 (s, 3H), 1.973 (s, 3H); 13C NMR (126 MHz, CDCl3) δ 138.720, 135.653, 134.941, 131.696, 130.086, 129.420, 127.631, 126.090, 124.975, 121.777, 115.397, 105.114, 21.185, 12.707, 11.065.

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Attached Files
PNP-pCH3-scheme.png
pCH3-aldehyde-1H.jpg
PNP-pCH3-IR.pdf
pCH3-final-1H.pdf
pCH3-final-13C.pdf
pCH3-aldehyde-1H.pdf
pCH3-aldehyde-1H.fid
pCH3-final-1H.fid
pCH3-final-13C.fid
PNP-pCH3.SPA