Eric Fossum (Committee Member), Daniel Ketcha (Committee Member), Kenneth Turnbull (Committee Chair)
Master of Science (MS)
Ortho-iodophenyl sydnones are key intermediates in Sonogashira coupling reactions and the resulting ortho alkynyl sydnones are useful precursors to functionalized sydnonquinolines. In this work, three synthetic routes leading to the synthesis of these versatile intermediates were explored.
Lithiation reactions of 3-(4-chlorophenyl) sydnone and 3-(4-methylphenyl) sydnone followed by trapping with iodine electrophiles yielded the expected disubstituted species 3-(4-chloro-2-iodophenyl)-4-iodosydnone and 3-(4-methyl-2-iodophenyl)-4-iodosydnone in yields ranging from 14% to 75%. Subsequent reduction with sodium sulfite removed the iodine at the C-4 position in both species yielding the ortho iodophenyl sydnones in 80% and 85% yield, respectively.
A surprising result was the discovery that careful reduction of 3-(4-chloro-2-iodophenyl)-4-iodosydnone and 3-(4-methyl-2-iodophenyl)-4-iodosydnone using sodium borohydride could generate the corresponding versatile ortho iodophenyl sydnones in 70% and 97 % yield, respectively.
Even more surprising, was the realization that careful manipulation of reactant quantities and physical parameters could generate the desired ortho-iodophenyl sydnones in yields ranging from 49% to 73% in a one step lithiation reaction. Interestingly, selective and non-selective desilylation of trisilylsydnones as well as disilylsydnones could be achieved using potassium carbonate or tetrabutylammonium fluoride.
Department or Program
Department of Chemistry
Year Degree Awarded
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