Three o-(dialkylaminomethy1)-benzeneboronic anhydrides are shown to be trimeric. Hydration of the corresponding anhydrides, which do not form complexes with pyridine, provides o-(N-morpholinomethy1)-and o-(dicyclohexylaminomethyl)-benzeneboronic acids. The latter acid shows remarkable stability to acid-catalyzed deboronation as well as dehydration. The structure of the compound, an o-methylenebridged ...