Uses
Twenty-one halo- and cyanopyrroles related to the trail pheromone of A. texana, Methyl 4-Methylpyrrole-2-carboxylate [34402-78-3], were prepared and tested by a faster and more sensitive bioassay than was previously available. Methyl 4-Chloropyrrole-2-carboxylate [1194-96-3] and Methyl 4-bromopyrrole-2-carboxylate appeared to be as active as the first one. Responsiveness of the ants in descending order to these compounds based on the constituent in the number two position, was: esters, methyl ketones, aldehydes.
Synthesis
General procedure for the synthesis of 4-bromo-1H-pyrrole-2-carbaldehyde from 2-pyrrolecarboxaldehyde: To a stirred solution of 1H-pyrrole-2-carbaldehyde (1 g, 10.52 mmol) in acetonitrile (10 mL) was slowly added N-bromosuccinimide (1.872 g, 10.52 mmol) at 0 °C. The reaction mixture was continued to be stirred at 0 °C for 15 min. Upon completion of the reaction, water was added to quench the reaction and the mixture was extracted with ether. The organic layers were combined, dried over anhydrous sodium sulfate and subsequently concentrated under reduced pressure. The crude product was recrystallized by mixed cyclohexane/ethanol solvent to afford 4-bromo-1H-pyrrole-2-carbaldehyde (41) as white crystals (1.125 g, 61% yield). The product characterization data were as follows: rf = 0.22 (dichloromethane as unfolding agent); melting point: 121-122 °C; 1H NMR (400 MHz, [D6]DMSO): δ 7.12 (m, 1H), 7.41 (m, 1H), 9.48 (s, 1H), 12.51 (bs, 1H); 13C NMR (100 MHz, [D6] DMSO): δ 97.0, 120.8, 126.5, 132.9, 179.1; IR (KBr): ν 3238, 3108, 2926, 2860, 1655, 1380, 1357, 1177, 1104, 920, 827, 771, 744, 598 cm-1; MS (ESI) m/z 173.9- 175.9 [M+H]+.
References
[1] Organic Letters, 2015, vol. 17, # 8, p. 1822 - 1825
[2] Journal of Medicinal Chemistry, 2015, vol. 58, # 18, p. 7286 - 7309
[3] Journal of Chemical Research, 2014, vol. 38, # 10, p. 593 - 596
[4] Patent: WO2017/20944, 2017, A1. Location in patent: Page/Page column 32
[5] Journal of Organic Chemistry, 2006, vol. 71, # 11, p. 4092 - 4102
