Propionic Acid → 5-bromo-1H-pyrrolo(2,3-b)pyridine-3-carbaldehyde

Participants

Reaction Steps

To a refluxing (oil bath temp. 140° C.) solution of hexamethylenetetramine (8.83 g, 63 mmol) in 66% aqueous propionic acid (31.5 mL) was added a mixture of 5 (16.0 g, 63 mmol) and hexamethylenetetramine (8.83 g, 63 mmol) in 66% propionic acid (47 mL) over 2.5 h. The reflux was continued for 2.5 h, the reaction mixture allowed to cool to room temperature, then poured onto water (220 mL) and the suspension cooled in an ice-bath. The solid was filtered off, washed with ice-cold water (2×), and dried under high vacuum overnight to give 6 as a white solid (11.47 g, 81%); 1H NMR (400 MHz, CDCl3+4 drops d4-MeOH) δ 9.91 (s, 1H), 8.69 (d, J=2.2 Hz, 1H), 8.36 (d, J=2.2 Hz, 1H), 7.95 (s, 1H).

Provenance & Evidence