Previously, we reported that the alkali metal reduction of alkyl isocyanates results in the formation of stable tri-alkyl isocyanurate anion radicals.  This cyclotrimerization is initiated by the isocyanate anion radical.  We have extended these studies to include aryl isocyanates and have found that ion association to the alkali metal cation is important to the reactivity of the aryl isocyanate anion radical.  Notably, when phenyl isocyanate (PhNCO) is reduced in tetrahydrofuran, the tri-phenyl isocyanurate anion radical is formed when K metal is used, but a pinacolate dianion is formed with Na metal.  This pinacolate is generated by the coupling of two PhNCO anion radicals; the strong electron-electron repulsion that results is stabilized by tight ion association to the Na+ ions.  This presentation will discuss the results obtained when PhNCO and 1-napthyl isocyanate are reduced with alkali metals, and the role of ion association in the reactivity of these anion radicals.

Reactivity of arylisocyanate anion radicals and the role of alkali metal ion association

244th National Meeting (2012)

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