Description:
<jats:p><jats:bold>Photoinduced Cycloadditions of 2,2‐Dimethyl‐3‐phenyl‐2<jats:italic>H</jats:italic>‐azirine with Nitriles and ‘push‐pull’ Olefines.</jats:bold></jats:p><jats:p>Electron deficient nitriles of the type <jats:bold>5a–e</jats:bold> in contrast to nonactivated nitriles undergo regiospecific [2+3]cycloadditions to benzonitrile isopropylide (<jats:bold>2b</jats:bold>), which was generated <jats:italic>in situ</jats:italic> by irradiation of 2,2‐dimethyl‐3‐phenyl‐2<jats:italic>H</jats:italic>‐azirine (<jats:bold>1b</jats:bold>), to yield the 2<jats:italic>H</jats:italic>‐imidazole derivatives <jats:bold>6a</jats:bold>–<jats:bold>e</jats:bold> (<jats:italic>Scheme 2</jats:italic>). The structure of the photoproducts was mainly deduced from <jats:sup>13</jats:sup>C‐NMR. and mass spectrometry.</jats:p><jats:p>Whereas normal olefins or enolethers do not react with <jats:bold>2b</jats:bold>, push‐pull olefins of the type <jats:bold>10a</jats:bold>–<jats:bold>d</jats:bold> readily undergo the cycloaddition to give the 3‐alkoxy‐5,5‐dimethyl‐2‐phenyl‐1‐pyrrolines <jats:bold>11a</jats:bold>–<jats:bold>d</jats:bold> (<jats:italic>Scheme 3 and 4</jats:italic>). The structure of the photoproducts <jats:bold>11a</jats:bold>–<jats:bold>d</jats:bold> indicates that the regiospecificity of the cycloaddition corresponds to that of acrylonitriles and acrylesters with <jats:bold>2b</jats:bold>.</jats:p>