Carol Y. Zhang and, J. Tour
Sep 11, 1999
Citations
0
Influential Citations
50
Citations
Journal
Journal of the American Chemical Society
Abstract
Several novel transformations on sensitive pyrazine cores are disclosed while preparing monomers for condensation polymerizations to planar polypyrazines. Two pyrazine monomers for the step growth polymerization are prepared starting from ethyl acetoacetate and proceeding via pyrazine-2,5-dicarboxylic acid as the common intermediate. The dicarboxylic acid serves as the key intermediate for the preparation of both the A and B components for the step-growth polymerization. A bis(Curtius) rearrangement followed by tert-butyl alcohol capture of the diisocyanate effects the high-yielding conversion of carbonyl moieties to the tert-butoxycarbonyl-protected aryldiamine. Since electrophilic halogenation of the pyrazine nucleus was unsuccessful due to the inherent electron deficiency of pyrazines, a directed ortho-metalation is disclosed using tert-butoxycarbonyl-protected amines and neopentyl glycol acetals as the metalation directing groups. Pd/Cu-catalyzed couplings of diiodopyrazines with distannylpyrazines ar...