Boulton-Katritzky rearrangement

What is Boulton-Katritzky rearrangement?

Boulton and Katritzky were the first to report the Boulton-Katritzky rearrangement in 1962. This rearrangement is a type of monocyclic rearrangement of heterocycles that can occur in the presence of an acid or a base, or under photoirradiation, and has been widely utilized in heterocyclic chemistry. It is sometimes referred to as the Boulton-Katritzky reaction.

Boulton-Katritzky rearrangement - Boulton-Katritzky reaction
Boulton-Katritzky rearrangement

A, C = N, N+-O, N+-N̄-R, C-R
B, D = O, NR, S

The reaction is believed to occur through a unimolecular one-step mechanism and has been suggested to be a [1,9]-sigmatropic rearrangement, although a recent computational study proposes that it is a pseudopericyclic reaction. It is worth noting that while the majority of reported rearrangements involve nitrogen atoms, a rearrangement involving sulfur atoms is also known, and computational studies have demonstrated that the pivotal nitrogen atom is not always necessary for the rearrangement to take place. The balance between substituted nitrobenzofuroxans is influenced by various factors, including steric, electronic, conformational, and strain effects.

The preparation of specific types of nitrogeneous heterocycles, such as nitrobenzofuroxans, has been a common application of Boulton-Katritzky rearrangement in heterocyclic chemistry. These compounds have been utilized in inhibiting nucleic acid and protein biosyntheses.


Boulton A.J., Katritzky A.R.
A new heterocyclic rearrangement,
(1962) Proceedings of the Chemical Society, 257