• photolysis;
  • quantum chemical calculations;
  • reactive intermediates;
  • singlet diradicals

In Scheme 1 of this Communication, formation of the MeO-migrated compound 10 a was reported for the photochemical denitrogenation of azoalkane AZ in benzene. 2D NMR spectroscopic analyses (HMBC, HMQC) of this reaction have now revealed that the product is not compound 10 a but compound 10 a′.

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The HMBC spectrum (see the Supporting Information) shows a clear correlation between the protons of one MeO group (δ=3.31 ppm) and one carbonyl carbon atom (δ=154.74 ppm) as well as the protons of another MeO group (δ=3.14 ppm) and enolic C4 carbon atom (δ=144.37 ppm). These correlations are not consistent with structure 10 a but with structure 10 a′.