Trifluoroacetic acid → Dipyrromethane

Participants

Reaction Steps

In a foil-covered 250-mL three-necked flask, equipped with a magnetic stirrer and a N2 inlet, was placed 2-thiazolecarboxaldehyde (13, 0.97 g, 8.6 mmol) (Dondoni, A.; Fantin, G.; Fogagnolo, M.; Medici, A.; Pedrini, P. Synthesis 1987, 998-1001), CH2Cl2 (35 mL), and pyrrole (7.2 mL, 104 mmol). The reaction mixture was stirred for 10 min, then TFA (0.26 mL, 3.4 mmol) was added. After a stirring period of 1 h at room temperature, the reaction mixture was transferred to a reparatory funnel and washed with saturated aqueous NaHCO3 (50 mL), H2O (50 mL), and brine (50 mL). The organic layer was dried (Na2SO4), filtered, and concentrated in vacuo. The residue was dissolved in CH2Cl2 (50 mL), and adsorbed onto silica gel (3 g). Purification by column chromatography (1:1 ether/hexanes) provided dipyrromethane 14 (1.22 g, 62%) as a solid: 1H NMR (300 MHz, CDCl3) δ 5.78 (s, 1 H), 6.04 (s, 2 H), 6.15 (m, 2 H), 6.71 (m, 2 H), 7.20 (d, 1 H), 7.74 (d, 1 H), 8.81 (br s, 1 H).

Provenance & Evidence