# Synthesis and Trapping of the Elusive Ortho-Iminoquinone Methide Derived from α-Tocopheramine and Comparison to the Case of α-Tocopherol

## TL;DR

This paper reports the successful synthesis and trapping of an elusive compound derived from α-tocopheramine, revealing new insights into its oxidation chemistry compared to α-tocopherol.

## Contribution

The study successfully synthesizes and confirms the existence of the elusive ortho-iminoquinone methide from α-tocopheramine.

## Key findings

- The ortho-iminoquinone methide was synthesized from α-tocopheramine and confirmed via dimerization and trapping.
- Suitable oxidation conditions enabled direct generation of the ortho-iminoquinone methide from α-tocopheramine.
- The oxidation chemistry of α-tocopherol and α-tocopheramine is compared and discussed.

## Abstract

Tocopheramines are a class of antioxidants which are distinguished from tocopherols (vitamin E) by the presence of an amino group instead of the phenolic hydroxyl group. α-Tocopheramine is intensively studied for biomedical applications but also as a stabilizer for synthetic and natural polymers, in particular for cellulose solutions and spinning dopes for cellulosic fibers. This study addresses a fundamental difference in the oxidation chemistry of α-tocopheramine and its tocopherol counterpart: while the formation of the ortho-quinone methide (o-QM) involving C-5a is one of the most fundamental reactions of α-tocopherol, the corresponding ortho-iminoquinone methide (o-IQM) derived from α-tocopheramine has been elusive so far. Synthesis of the transient intermediate succeeded initially via 5a-hydroxy-α-tocopheramine, and its occurrence was confirmed by dimerization to the corresponding spiro-dimer and by trapping with ethyl vinyl ether. Eventually, suitable oxidation conditions were found which allowed for the generation of the o-IQM directly from α-tocopheramine. The underlying oxidation chemistry of α-tocopherol and α-tocopheramine is concisely discussed.