Synthesis of carboxylic acids based on the closo-decaborate anion

A series of new boron-containing carboxylic acids was prepared by the ring-opening reaction of cyclic oxonium derivatives of the c/oso-decaborate anion [B10H10](2-) with methyl esters of hydroxybenzoic acids or the cyanide anion followed by hydrolysis of the obtained nitrile and esters. Acid hydrolysis of the esters results in protonation of the oxygen atom connected to the boron cage, with the formation of the corresponding P-protonated acids, isolated in the solid state. The compounds synthesized can be used in radionuclide diagnostics and boron neutron capture therapy of cancer. (C) 2011 Elsevier Ltd. All rights reserved.