Synthesis
The general procedure for the synthesis of di(1H-pyrrol-2-yl)methane from pyrrole and formaldehyde was as follows: paraformaldehyde (0.5 g, 16.7 mmol) was added to pyrrole (118 mL, 1.67 mol) as a solvent, followed by the addition of catalyst indium(III) chloride (370 mg, 1.67 mmol). The reaction mixture was stirred at room temperature for 10 h under argon protection. Subsequently, the reaction system was warmed up to 55 °C and stirring was continued for 6 hours. After completion of the reaction, sodium hydroxide (NaOH, 0.2 g, 83.5 mmol) was added and stirred for 4 hours. The reaction mixture was filtered and the filtrate was concentrated. The residue was purified by column chromatography using dichloromethane: hexane (1:1, v/v) as eluent to afford 2.05 g (yield: 84%) of the target compound di(1H-pyrrol-2-yl)methane as a white solid.
References
[1] Tetrahedron, 2011, vol. 67, # 26, p. 4924 - 4932
[2] Monatshefte fur Chemie, 2004, vol. 135, # 10, p. 1265 - 1273
[3] Patent: KR101545325, 2015, B1. Location in patent: Paragraph 0096-0100
[4] Journal of the American Chemical Society, 2014, vol. 136, # 51, p. 17802 - 17807
[5] Angewandte Chemie - International Edition, 2015, vol. 54, # 2, p. 691 - 695
