Trifluoroacetic acid → Dipyrromethane

In a foil-covered 250-mL three-necked flask, equipped with a magnetic stirrer and N2 inlet, was placed 5-thiazolecarboxaldehyde (1, 0.88 g, 7.81 mmol) (Dondoni, A.; Fantin, G.; Fogagnolo, M.; Medici, A.; Pedrini, P. Synthesis 1987, 998-1001), CH2Cl2 (30 mL), and pyrrole (6 mL, 87 mmol). The reaction mixture was stirred for 10 min, then TFA (0.25 mL, 3.2 mmol) was added. After a stirring period of 2 h at room temperature, the reaction mixture was transferred to a separatory 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 (gradient elution 33-67% EtOAc/hexanes) provided dipyrromethane 2 (0.95 g, 52%) as a gray solid: 1H NMR (300 MHz, CDCl3) δ 5.74 (s, 1H), 6.02 (m, 2H), 6.17 (m, 2H), 6.70 (m, 2H), 7.58 (s, 1H), 8.19 (br s, 2H), 8.68 (s, 1H).

1. customIn a foil-covered 250-mL three-necked flask, equipped with a magnetic stirrer and N2 inlet
2. waitAfter a stirring period of 2 h at room temperature
3. customthe reaction mixture was transferred to a separatory 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
10. washby column chromatography (gradient elution 33-67% EtOAc/hexanes)

ORD record

ord-d6d757de794e460a85ff55c6f39e4c96

Source dataset

uspto-grants-2015_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08946202B2