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14th November 2013 @ 17:25

reaction scheme

1-(3-methylphenyl)-2,5-dimethylpyrrole: m-Anisidine (5 mmol, 0.57mL) was added to 2,5-hexanedione (4.5 mmol, 0.53mL) and heated to 130ºC overnight. The reaction was combined with ether (10 mL) and citric acid (10 mL) in a separatory funnel, and the organic layer was washed with water (10 mL) followed by sodium chloride (10 mL). The organic layer was then dried over magnesium sulfate (MgSO4) and filtered. Evaporation of the solvent was followed by the addition of methanol (1 mL) and purification by flash chromatography (silica gel, hexanes-ethyl acetate, 8:1) to give the title compound as a yellow oil (350 mg, 35%). 1H NMR (400 MHz, CDCl3) δ 7.338 (t, 1H), 6.943 (dd, 1H), 6.807 (dd, 1H), 6.753 (d, 1H), 5.891 (s, 2H), 3.804 (s, 3H), 2.045 (s, 6H).

1-(3-methylphenyl)-2,5-dimethylpyrrole-3-carboxaldehyde: Phosphoryl chloride (0.192 mL) was added to dimethylformamide (1 mL), stirring on ice and under a nitrogen atmosphere for 25 minutes. Dimethylformamide (1 mL) was added to the crude compound 1; this was added dropwise to the stirring reaction on ice. Using TLC (hexanes-ethyl acetate, 3:1) to monitor, upon completion the reaction was poured over ice. The pH was adjusted to 11 using NaOH (10%), followed by an aqueous workup where the reaction was first combined with NaOH. Ethyl acetate was added to the aqueous layer, and the two organic layers were combined; water was added, and the organic layer was then combined with a saturated brine solution. This was dried over MgSO4 and filtered. The solvent was evaporated under reduced pressure to give compound 2 as a colorless oil (117 mg, 29%). 1H NMR (400 MHz, CDCl3) δ 9.868 (s, 1H), 7.418 (t, 1H), 7.02 (m, 1H), 6.79 (m, 1H), 6.731 (ds, J = 2 Hz, 1H), 6.375 (s, 1H), 3.847 (s, 3H), 2.299 (s, 3H), 2.008 (s, 3H); IR υmax  2921.16, 2837.17, 1734.73, 1654.77 cm-1.

Final Product: (Z)-2-((3-phenyl)imino)thiazolidin-4-one (96 mg) was dissolved in ethanol (2 mL) and piperdine (0.078 mL) was added. This was combined with the aldehyde above (115 mg) and heated to 60ºC. The reaction was monitored using TLC (hexanes-ethyl acetate, 3:1) and after 4.5 hours, the product precipitated out. This was filtered and washed with ethanol to give compound 3 as a tan powder (68 mg, m.p. 251-255°C, 33%). 1H NMR (400 MHz, CDCl3) δ 7.73 (s, 1H), 7.40 (m, 3H), 7.8 (m, 3H), 6.99 (m, 1H), 6.75 (m, 1H), 6.69 (t, 1H), 3.83 (s, 3H), 2.16 (s, 3H), 2.00 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 160.362, 138.665, 135.444, 131.565, 130.179, 129.420, 125.022, 121.808, 120.151, 115.505, 114.321, 113.740, 105.230, 55.519, 12.668, 11.050; IR υmax 2961.47, 2793.77, 1683.33, 1622.90 cm-1.

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