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UBC Theses and Dissertations

Synthesis and polymerization of spiro-orthoesters catalyzed by a cationic indium complex Chang, Chen


While numerous neutral indium complexes have been reported to be functional group tolerant Lewis acid catalysts for various transformations, there are only a handful of reported cationic indium complexes; these are mostly inactive in catalytic transformations. Herein, I describe the synthesis and characterization of a rare cationic indium alkyl complex bearing a chiral tridentate ligand, [(NNO)In(CH₂SiMe₃)(THF)][BArF] (30). Complex 30 is active towards reaction of 1,2-epoxy-7-octene and ε-caprolactone to form the corresponding spiro-orthoester (SOE1), where quantitative conversions of both substrates are achieved under 24 hours at 2.5% catalyst loading at 60 ˚C in benzene. Synthesis of spiro-orthoesters bearing various ether rings are also achieved with different lactone substrates. While preliminary polymerization studies of SOE1 by the cationic indium species 30 suggest the poor activity of this system towards polymerization of SOE1 at low temperature, polymerization of SOE1 complex 30 at 110 ˚C resulted in over 90% conversion of the monomer, and the resulting polymer was tentatively assigned as low molecular weight poly(ether ester). This thesis provides another example of the unusual reactivity of cationic indium complexes, where further investigation of various spiro-orthoesters synthesis and polymerization, as well as exploration of other cationic indium complexes, will be continued in the Mehrkhodavandi group.

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