Dehydration of ortho-, meta- and para-Alkoxy Phenylboronic Acids to their Corresponding Boroxines

Isomeric isobutoxy phenylboronic acids (ortho-, meta-, para-) were synthesized and their properties such as pK(a) and thermal stability have been compared. Molecular and crystal structures of the para isomer were determined by single crystal XRD methods. DSC and TGA measurements have been carried out on all isomers to study their dehydration as well as thermal stability. The results show that the position of the substituent in phenylboronic acids influences their acidity as well as possible formation of the corresponding boroxines.