Derivatives of closo–[B12H12]2– anion show promise first as compounds used for the treatment of cancers by 10B-neutron capture therapy (BNCT) [1]. The BNCT is based on the selective accumulation of 10B isotope atoms in tumor cells and subsequent irradiation of them with slow neutron fluence. High energy particles resulting from the nuclear reaction 10B + 1n  [11B]  4He + 7Li + Q, which are characterized by shorter ranges as compared to cell dimensions, destruct tumor cells. The principal requirements for the boron containing drug are their selectivity and high content in tumor. Derivatives of [B12H12]2– anion are the most adequate candidates for the application for BNCT since they exhibit high chemical and biological stability, are characterized by high boron content per molecule, and as a rule low toxicity. 1,2–[B12H10(OH)2]2– hydroxy derivative can be synthesized by alkali hydrolysis of 1,2–[C6H5CH2C(O)OB12H10OH]2– anion [2]. During heating at 80 С, a parent anion salt mixed with acetone and concentrated hydrochloric acid gives a mixture of 1,2– and 1,7–isomers of [B12H10(OH)2]2– hydroxy derivatives [3]. We consider the interaction between bis(tetrabutilammonium) dodecagidro–closo–dodecaborate (2–), (TBA)2[B12H12] and benzene–1,2–dicarboxylic acid during holding at 190–195 С in a dry argon atmosphere followed by alkaline hydrolysis of the formed intermediate. In the course of found reaction benzene–1,2–dicarboxylic acid is both reagent and solvent. Product was identified by elemental analysis, IR spectroscopy (2 475 cm–1 B–H; 3 653, 3 645 cm–1 O–H; 1 011 cm–1 B–B), and 11B NMR spectroscopy (CD3CN) {3.72 (s; B1, B2); –16.16 (d; B3, B6; 1J(11B,1H) = 121.3); –18.13 (d; B4, B5, B7, B11; 1J(11B,1H) = 126.8); –21.51 (d; B8, B10; 1J(11B,1H) = 129.1); –25.23 (d; B9, B12; 1J(11B,1H) = 129.1)}.