Synthesis of triazolyl methyl-substituted amino- and oxy-undeca-hydro-dodeca-borates for potential application in boron neutron capture therapy

A general approach to the synthesis of triazole conjugates containing undeca-hydro-closo-dodeca-borate anions based on Huisgen 1, 3-dipolar cycloaddition is presented. Un-decahydro-closo-dodeca-borate anions bearing terminal alkyne groups were synthesized by the reaction of H3N-B12H11- or HO-B12H112- with alkyne halides in N, N-dimethylformamide using KOH as a base. Variation of reaction time, alkyne halide concentration and steric demands of the alkyne halide resulted in the stepwise introduction of one to three alkyne groups into H3N-B12H11-. Two compounds {(CHCCH2)-N-B12H11- and (CHCCH2)O-B12H112-} were crystallized for single-crystal X-ray diffraction studies. N- and O-alkyne un-decahydro-closo-dodeca-borate anions reacted with various functionalized azides including lipid, carborane, aryl and hydroxyalkyl groups. The current study provides various synthetic applications not only for BNCT but also for boron cluster materials. (authors)