Cu-Free 1,3-Dipolar Cycloaddition Click Reactions To Form Isoxazole Linkers in Chelating Ligands for <i>fac</i>-[M<sup>I</sup>(CO)<sub>3</sub>]<sup>+</sup> Centers (M = Re, <sup>99m</sup>Tc)
作者:Shalina C. Bottorff、Benjamin B. Kasten、Jelena Stojakovic、Adam L. Moore、Leonard R. MacGillivray、Paul D. Benny
DOI:10.1021/ic402825t
日期:2014.2.17
Isoxazole ring formation was examined as a potential Cu-free alternative click reaction to Cu-I-catalyzed alkyne/azide cycloaddition. The isoxazole reaction was explored at macroscopic and radiotracer concentrations with the fac-[M-I(CO)(3)](+) (M = Re, Tc-99m) core for use as a noncoordinating linker strategy between covalently linked molecules. Two click assembly methods (click, then chelate and chelate, then click) were examined to determine the feasibility of isoxazole ring formation with either alkyne-functionalized tridentate chelates or their respective fac-[M-I(CO)(3)](+) complexes with a model nitrile oxide generator. Macroscale experiments, alkyne-functionalized chelates, or Re complexes indicate facile formation of the isoxazole ring. Tc-99m experiments demonstrate efficient radiolabeling with click, then chelate; however, the chelate, then click approach led to faster product formation, but lower yields compared to the Re analogues.
pH-Controlled Coordination Mode Rearrangements of “Clickable” Huisgen-Based Multidentate Ligands with [M<sup>I</sup>(CO)<sub>3</sub>]<sup>+</sup> (M = Re, <sup>99m</sup>Tc)
作者:Shalina C. Bottorff、Adam L. Moore、Ariana R. Wemple、Dejan-Krešimir Bučar、Leonard R. MacGillivray、Paul D. Benny
DOI:10.1021/ic302330u
日期:2013.3.18
2-[(pyridin-2-ylmethyl)amino]acetic acid (PMAA) ligand system, 3, and fac-[MI(OH2)3(CO)3]+ (M = Re, 99mTc). Two synthetic strategies, (1) click, then chelate and (2) chelate, then click, were investigated to determine the impact of assembly order on the reactivity of the system. In the click, then chelate approach, fac-[MI(OH2)3(CO)3]+ was reacted with the PMAA ligand “clicked” to the benzyl azide, 5, to yield