Journal of Medicinal Chemistry, 1990, Vol. 33, No. 1, page 392Indole-3-acetaldehyde (1) was prepared by a modification
15 of the published procedure:
16A solution of 3.052 g (14.9 mmol) of DL-tryptophan in 100 ml water and 15 ml of 10% NaOH (aq) was prepared in a 2-L beaker.
This solution was stirred mildly at room temperature with a mechanical stirrer, and 10 ml of 4 N HCl (aq) was added to bring the pH to 9-10 after tryptophan has dissolved.
The solution was diluted with 350 ml of water, 250 ml of brine, and 400 ml of benzene. The mixture was stirred and heated to 43-45°C, and 200 ml of a 0.52% NaOCl (aq) solution (10% solution of commercial Chlorox) was added dropwise over a period of 30 min.
Following the addition, another 100 ml of benzene was added 5 min before the end of the stirring.
The warm solution was transferred to a separatory funnel, and the layers were seperated. The aqueous phase was extracted with 200 ml, 150 ml, and 100 ml of benzene. The combined benzene extracts were extracted with 75 ml of brine, dried (Na
2SO
4), and concentrated to give 1.765 g (74%) of crude 1 as a viscous yellow oil.
This was purified by flash chromatography (44 g of silica, acetone/pentane, from 1:9 to 2:
to yield 1.0548 g (44%) of the known
16 1 as viscous yellow oil.
(15) Tsarouthis, D. B.S., Thesis, Polytechnic University, 1968
(16) Arch. Biochem. Biophys. 1959, 81, 480 [see above]; J. Labelled Compd. Radiopharm. 1981, 18, 1491
Comment by Lego:
Benzene is carcinogenic, perhaps toluene or xylene should work too.
This method should also work with NaOCl on clay. See
Post 422851
(Lego: "Oxidation of Amines to Aldehydes on Clay with...", Novel Discourse)