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Cu-Free 1,3-Dipolar Cycloaddition Click Reactions To Form Isoxazole Linkers in Chelating Ligands for fac-[MI(CO)3]+ Centers (M = Re, 99mTc)
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Cu-Free 1,3-Dipolar Cycloaddition Click Reactions To Form Isoxazole Linkers in Chelating Ligands for fac-[MI(CO)3]+ Centers (M = Re, 99mTc)

Shalina C Bottorff, Benjamin B Kasten, Jelena Stojakovic, Adam L Moore, Leonard R MacGillivray and Paul D Benny
Inorganic chemistry, Vol.53(4), pp.1943-1945
02/17/2014
DOI: 10.1021/ic402825t
PMCID: PMC3993946
PMID: 24483834
url
https://doi.org/10.1021/ic402825tView
Published (Version of record) Open Access

Abstract

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, 99m Tc) 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. 99m Tc 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. Isoxazole ring formation was examined as a potential Cu-free alternative click scheme to CuAAC reactions at macroscopic and radiotracer concentrations with fac -[M I (CO) 3 ] + (M = Re, 99m Tc) for use as a noncoordinating linker 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.
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