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14th November 2013 @ 17:30
4-(2,5-Dimethyl-1H-pyrrol-yl)benzonitrile: 4-aminobenzonitrile (1.36 g, 10 mmol), 2,5-hexanedione (1.4 mL, 12 mmol) and sulfamic acid (50 mg, 0.5 mmol, 5 mol%) combined in capped tube and heated to 130 °C overnight. Solid recrystallized from hot ethanol to give a tan powder (1.403 g, 63%). 4-(3-Formyl-2,5-dimethyl-1H-pyrrol-1-yl)benzonitrile (FPBC): DMF (0.40 mL) was stirred with phosphoryl chloride (0.14 mL, 1.5 mmol,) at 0 °C under a nitrogen atmosphere. 4-(2,5-Dimethyl-1H-pyrrol-yl)benzonitrile (PBC) (196 mg, 1.0 mmol,) in DMF (0.40 mL) was added dropwise over 5 min. Once the reaction reached completion (20 min, monitored by TLC), the solution was poured over ice (4 mL) and the pH brought to 8 (approx. 10% NaOH). Once fully reacted (30 min) the reaction was filtered and the resulting grey crystal purified with MeCN and filtered affording FPBC (90 mg, 40%) as a brown crystal: FTIR (neat) 3094, 3060, 2956, 2923, 2837, 2755, 2229, 1651, 1603 cm-1; 1HNMR (400 MHz, CDCl3) δ 9.90 (s, 1H), 7.86 (d, 2H, J = 8.4 Hz), 7.36 (d, 2H, J = 8.4 Hz), 6.42 (s, 1H), 2.29 (s, 3H), 2.01 (s, 3H). mp 162.4-163.9. Nitrile Thiazolidinone Pyrrole (NTP): Dissolved FPBC (72 mg, 0.32 mmol) and (Z)-2-((3-phenyl)imino)thiazolidin-4-one (61 mg, 0.32 mmol) in EtOH (4.8 mL). Piperidine (0.048 mL, 0.48 mmol) was added and the solution heated to 60 °C. Upon reaction completion (90 min) the solution was cooled to room temperature and filtered and the solid precipitate washed with EtOH yielding NTP (57 mg, 49%) as a yellow solid: FTIR (neat) 3066, 2978, 2792, 2232, 1700, 1641, 1600 cm-1; 13C NMR (399 MHz, CDCl3) δ 165.3, 163.3, 141.6, 134.4, 133.3, 131.0, 129.4, 128.9, 126.6, 125.1, 121.9 117.7, 116.5, 112.8, 106.4, 110.5, 12.8, 11.2. mp 315 (dec.) 1H NMR (DMSO-d6, at 60 C, which is much cleaner than that at ambient temperatures -- hindered rotation of aromatic rings?  cis-trans isomerization in the enone or imine?): 11.5 (br s, 1H), 7.99 (d, 2H, J=8.6 Hz), 7.53 (apparent d, 3H), 7.38 (apparent t, 2-3H), 7.15 (apparent t, 2H), 6.10 (s, 1H), 2.10 (s, 3H), 1.97 (s, 3H).
Attached Files
pCN-aldehyde-1H.pdf
PNP-CN-final-1H-60C.fid
pCN-aldehyde-1H.fid
pCN-final-60C-1H.pdf
PNP-CN-scheme.png
PNP-pCN-IR.pdf
PNP-pCN.SPA