Trifluoroacetic acid → Dipyrromethane

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).

1. customIn a foil-covered 250-mL three-necked flask, equipped with a magnetic stirrer and a N2 inlet
2. waitAfter a stirring period of 1 h at room temperature
3. customthe reaction mixture was transferred to a reparatory funnel
4. washwashed with saturated aqueous NaHCO3 (50 mL), H2O (50 mL), and brine (50 mL)
5. dry with materialThe organic layer was dried (Na2SO4)
6. filtrationfiltered
7. concentrationconcentrated in vacuo
8. dissolutionThe residue was dissolved in CH2Cl2 (50 mL)
9. customPurification by column chromatography (1:1 ether/hexanes)

ORD record

ord-30734b3c931a4e6eb9f4ebf798abe1a7

Source dataset

uspto-grants-2016_03

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US09289434B2