Solubility of phenylboronic compounds in water

Solubility of six phenylboronic compounds in water was investigated using different methods. The results are consistent with each other, although for particular compounds selected methods should be preferred. The solubility of the investigated compounds is low, with the value of ca. 2 g/100 cm3 H2O at 20°C for unsubstituted phenylboronic acid. The unsubstituted benzoxaborole is less soluble than phenylboronic acid. Introduction of OiBu, COOH and CF3 groups into the phenyl ring decreases solubility in comparison with unsubstituted phenylboronic acid, especially for the alkoxy substituent.