Propionic Acid → 1H-Pyrrolo[3,2-b]pyridine-3-carbaldehyde

Participants

Reaction Steps

A solution of 3-dimethylamino-1H-pyrrolo[3,2-b]pyridine (1.53 g) and hexamethylenetetramine (1.22 g) in 6.68 g of 66% propionic acid was added dropwise to a refluxing solution of 2.44 g of hexamethylenetetramine in 8.92 g of the same solvent. The addition was carried out over a period of one hour and the solution was refluxed 3.5 hours more. The solution was concentrated in vacuo and thereto water (30 ml), ethyl acetate (25 ml), and tetrahydrofuran (20 ml) were added. The organic layer was separated, dried over sodium sulfate, and concentrated under reduced pressure. The resulting residue was purified by column chromatography on silica gel (12 g) using a mixed solvent of dichloromethane and methanol (0.15:1). The fractions containing the objective compound were collected and evaporated under reduced pressure to give a powder of 3-formyl-1H-pyrrolo[3,2-b]pyridine (0.45 g).

Provenance & Evidence