Synthesis of an Isotopically Labeled Naphthalene Derivative
That Supports a Long-Lived Nuclear Singlet State
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Abstract
The synthesis of an octa-alkoxy substituted
isotopically labeled
naphthalene derivative, shown to have excellent properties in singlet
NMR experiments, is described. This highly substituted naphthalene
system, which incorporates an adjacent <sup>13</sup>C spin pair, is
readily accessed from a commercially available <sup>13</sup>C<sub>2</sub>-labeled building block via sequential thermal alkynyl- and
arylcyclobutenone rearrangements. The synthetic route incorporates
a simple desymmetrization approach leading to a small difference in
the chemical shifts of the <sup>13</sup>C spin pair, a design constraint
crucial for accessing nuclear singlet order