# Heterocyclizations at the Isocyanide Carbon: Mechanistic Insights into the 2‑Isocyanoaniline to Benzimidazole Conversion

## TL;DR

This paper explores how a specific chemical conversion from isocyanoaniline to benzimidazole occurs, revealing a possible new reaction pathway.

## Contribution

The study provides a computational analysis of a previously unclear reaction mechanism involving isocyanoaniline cyclization.

## Key findings

- A transient 1,4-diazabutatriene intermediate is proposed to lower the reaction barrier in the cyclization.
- The reaction pathway involving the intermediate is more plausible than a unimolecular concerted process.

## Abstract

Benzo-fused heteroazacycles can form through spontaneous
cyclizations
of phenylisocyanides bearing some electron donor substituents at the ortho position. Although such reactions have been known
since the 1970s, a clear mechanistic understanding of these transformations
remains absent. Here, we disclose a detailed computational analysis
aimed at elucidating the more plausible mechanism for one of these
cyclizations, the o-isocyanoaniline to benzimidazole
conversion. Our results show that a transient 1,4-diazabutatriene
could play a key role in this cyclization by enabling a reaction pathway
of lower barrier than the unimolecular concerted process.