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Aryl Boroxines via Rotary Evaporation
1University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh, EH9 3FJ, U.K.
Organic Letters
|June 25, 2026
Summary
A new method rapidly converts aryl boronic acids to aryl boroxines using rotary evaporation. This simple pretreatment strategy efficiently controls speciation for improved chemical synthesis.
Area of Science:
- Organic Chemistry
- Materials Science
Background:
- Aryl boroxines are crucial intermediates in organic synthesis.
- Traditional methods for aryl boroxine preparation are time-consuming and require harsh conditions (thermal-vacuum or azeotropic dehydration).
- The equilibrium between aryl boronic acids and aryl boroxines is sensitive to reaction conditions.
Purpose of the Study:
- To develop a rapid, efficient, and simple method for preparing aryl boroxines from aryl boronic acids.
- To establish a pretreatment strategy for controlling the speciation of aryl boronic acids/boroxines.
Main Methods:
- Investigated the rapid equilibrium between aryl boronic acids and aryl boroxines in solution and amorphous solid states.
- Employed rotary evaporation of tetrahydrofuran (THF) solutions at ambient temperature (<50 mbar, 50 °C, 220 rpm, 30 min) to drive the equilibrium towards boroxine formation.
Main Results:
- The equilibrium between aryl boronic acids and aryl boroxines is rapidly achieved in solution at ambient temperature and in the amorphous solid state upon gentle warming.
- Rotary evaporation of THF solutions efficiently converted aryl boronic acids to aryl boroxines, achieving >95-99% yield.
- This method provides a simple and effective pretreatment strategy for controlling speciation.
Conclusions:
- Rotary evaporation offers a significantly faster and simpler alternative to conventional methods for aryl boroxine synthesis.
- This technique allows for efficient control over the boronic acid/boroxine equilibrium, facilitating predictable speciation.
- The developed method is suitable as a pretreatment strategy in various chemical applications requiring specific boroxine forms.
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