# Triggering and Preventing Cyclization of o‐Amino‐Guanidinobenzenes to 2‐Amino‐Benzimidazoles

## TL;DR

This paper explores how to prevent unwanted chemical reactions in certain aromatic compounds, enabling their use in new types of chemical applications.

## Contribution

The study provides strategies to prevent cyclization of o-amino-guanidinobenzenes using acid control and structural modifications.

## Key findings

- Cyclization of o-amino-guanidinobenzenes is triggered by Brønsted and Lewis acids.
- Strategies to prevent cyclization involve careful selection of the guanidino group and amino substituents.
- Unsymmetrical diguanidinobenzene molecules and coordination compounds were successfully synthesized.

## Abstract

Aromatic compounds in which a primary or secondary amino group is positioned next (in ortho position) to a guanidino group have been reported as intermediates in a variety of reactions, but are generally prone to cyclization to give 2‐amino‐imidazoles. Here, we present a comprehensive analysis, based on experiments and quantum‐chemical calculations, of the stability and reactivity of these compounds. It is shown that cyclization reactions are triggered by Brønsted and Lewis acids. The analysis discloses strategies allowing to prevent cyclization by careful choice of the guanidino group and/or substituent at the amino group. The results of this analysis allowed the synthesis of first unsymmetrical diguanidinobenzene molecules and coordination compounds with o‐amino‐guanidinobenzene ligands, paving the way for the development of aromatic compounds with adjacent amino and guanidino groups as a versatile class of redox‐active organic molecules.

o‐Amino‐guanidinobenzenes are generally prone to cyclization to 2‐amino‐benzimidazoles. In this work, strategies to prevent such cyclizations are developed, allowing to use these compounds as ligands in coordination chemistry and for the design of novel (unsymmetrical) redox‐active ligands.