Redox-Neutral Selenium-Catalysed Isomerisation of para-Hydroxamic Acids into para-Aminophenols.

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• N-aryl-hydroxamic acids are versatile synthetic intermediates.
• Efficient synthesis of para-aminophenol derivatives remains a key challenge in organic chemistry.
• Existing methods for para-hydroxylation often require harsh conditions or lack selectivity.

Purpose of the Study:

• To develop a novel, selenium-catalyzed method for the para-hydroxylation of N-aryl-hydroxamic acids.
• To elucidate the reaction mechanism, including N-O bond cleavage and selenium-induced rearrangement.
• To provide an unconventional synthetic route to valuable para-hydroxyaniline derivatives.

Main Methods:

• Selenium-catalyzed reaction of N-aryl-hydroxamic acids.
• Mechanistic studies utilizing oxygen-18 (¹⁸O) crossover experiments.
• Computational analysis using quantum chemical calculations.

Main Results:

• Successful para-hydroxylation of N-aryl-hydroxamic acids was achieved using a selenium catalyst.
• The reaction proceeds via N-O bond cleavage followed by a selenium-mediated [2,3]-rearrangement.
• ¹⁸O-crossover experiments and quantum chemical calculations confirmed the proposed mechanism.

Conclusions:

• A novel and efficient selenium-catalyzed redox-neutral transformation for synthesizing para-hydroxyaniline derivatives has been established.
• The study provides significant mechanistic insights into selenium-mediated rearrangements.
• This work offers an unconventional and valuable synthetic approach to para-aminophenols.