Background: In the past decades, mechanochemical organic synthesis has become
an attractive technique for solvent-free synthesis, which avoids the usage of harmful
solvents and production of toxic wastes. This method has been utilized to promote the efficient
formation of carbon–carbon and carbon–heteroatom bonds. The mechanochemical
synthesis of macrocyclic molecules, rotaxanes and covalent organic frameworks has been
reported recently. However, the mechanochemical construction of purely organic cage
compounds is scanty and challenging.
Objective: The primary objective of this study was to synthesize boronic ester cage compounds
under high-speed vibration milling conditions and investigate their properties.
Method: A mixture of triboronic acids 3 (0.04 mmol) and pentaerythritol (0.06 mmol) was vigorously shaken
under high-speed vibration milling (HSVM) conditions at 58 Hz for 40 min. The resulting solid was dissolved
in chloroform (5 mL) and then filtered. Cage compounds 4 were obtained by removal of the solvent, and dried
under vacuum at 100 °C for 12 h. Cage compounds 4 were subjected to thermogravimetric analysis and chemical
Result: Boronic ester cage compounds 4 were synthesized in nearly quantitative yields under high-speed vibration
milling conditions. Furthermore, thermogravimetric analysis and chemical stability experiments showed
that cage compounds 4 possessed high thermal stability (Tdec up to 320 °C) and good chemical stability in
Conclusion: We have described an efficient solvent-free synthesis of boronic ester cage compounds 4 under
the HSVM conditions. Furthermore, cage compounds 4 possessed high thermal stability and good chemical
stability in aqueous media.