Synthesis and Structure of Nido-Carboranyl Azide and Its “Click” Reactions

Novel zwitter-ionic nido-carboranyl azide 9-N(3)(CH(2))(3)Me(2)N-nido-7,8-C(2)B(9)H(11) was prepared by the reaction of 9-Cl(CH(2))(3)Me(2)N-nido-7,8-C(2)B(9)H(11) with NaN(3). The solid-state molecular structure of nido-carboranyl azide was determined by single-crystal X-ray diffraction. 9-N(3)(CH(2))(3)Me(2)N-nido-7,8-C(2)B(9)H(11) was used for the copper(I)-catalyzed azide-alkyne cycloaddition with phenylacetylene, alkynyl-3β-cholesterol and cobalt/iron bis(dicarbollide) terminal alkynes to form the target 1,2,3-triazoles. The nido-carborane-cholesterol conjugate 9-3β-Chol-O(CH(2))C-CH-N(3)(CH(2))(3)Me(2)N-nido-7,8-C(2)B(9)H(11) with charge-compensated group in a linker can be used as a precursor for preparation of liposomes for Boron Neutron Capture Therapy (BNCT). A series of novel zwitter-ionic boron-enriched cluster compounds bearing a 1,2,3-triazol-metallacarborane-carborane conjugated system was synthesized. Prepared conjugates contain a large amount of boron atom in the biomolecule and potentially can be used for BNCT.