Hexamethylenetetramine → Benzo(b)thiophene-5-carboxaldehyde

Participants

Reaction Steps

Under N2, NBS (6 g, 0.034 mol) was added to a solution of 5-methylbenzo[b]thiophene (30.8 g, 0.21 mol), benzoylperoxide (1.6 g) in CCl4 (300 ml) and was heated at reflux. After 15 minutes, the remainder of the NBS (35 g, 0.2 mol) was added over a period of 5 minutes and heated at reflux for 1.5 hours. The reaction mixture was then cooled, filtered and the filtrate washed with H2O (2x), dried, filtered and concentrated to dryness. The residue was dissolved in CHCl3 (130 ml) and added to a solution of hexamethylenetetramine (33.6 g, 0.24 mol) in CHCl3 (60 ml). After 0.5 hour, the reaction mixture was cooled, filtered and the solid washed with hexane. After drying, the solid was dissolved in acetic acid-H2O (275 ml) and heated at reflux for 2 hours. The concentrated HCl (55 ml) was added and the mixture refluxed an additional 5 minutes. After cooling, the solution was extracted with ether (3x), and the organic extracts were backwashed with saturated Na2CO3 (2x), dried, filtered, and concentrated to dryness to yield 16.4 g (48%) of product.

Provenance & Evidence