Reexamination of the Bromination of 2-Nitrobenzaldehyde with NBS or NaBr-NaIO₄ in Sulfuric Acid

Abstract

Two literature procedures for selective bromination of 2-nitrobenzaldehyde using N-bromosuccinimide (NBS) or NaBr-NaIO₄ in sulfuric acid were examined. In contrast to the reports that 4-bromo-2-nitrobenzaldehyde is formed as a single product in good yield, reactions using NBS gave a number of isomeric mono- and dibrominated products identified by spectroscopical methods and by sodium borohydride reduction to the corresponding benzyl alcohol, and reactions using NaBr-NaIO₄ did not furnish any product.

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GRAPHICAL ABSTRACT

Keywords:

• Bromination
• N-bromosuccinimide
• nitrobenzaldehyde

Notes

^a The first number represents the molar ratios of products from ¹H NMR spectra of crude reaction mixtures.

^b The number in parenthesis represents isolated yields of products after chromatography. Yields in parentheses and italics were calculated from ¹H NMR spectra of mixtures.

^c The brominations were performed at ambient temperature.

^d Bromination at 60 °C.