Diazoalkanes, hydrogen-deuterium

Hydrogen-deuterium exchange in diazoalkanes, 53, 43 HYDROGENOLYSIS OF CARBON-HALO-GEN BONDS WITH CHROMIUM (II)-EN PERCHLORATE NAPHTHALENE FROM 1—BROMONAPHTHALENE, 52, 62... 

The procedure described provides a general method for the hydrogen-deuterium exchange of simple diazoalkanes. 

As expected, the product ratios were quite different in acetonitrile and acetonitrile-ris. For example, the major products were diphenylmethane and benzophenone and only a small amount of benzophenone azine when the reaction was carried out in acetonitrile whereas the percentage of benzophenone azine was ten times larger, i.e. almost equal to the diphenylmethane when the solvent was acetonitrile-hydrogen-deuterium kinetic isotope effect in acetonitrile-ris slows the hydrogen abstraction reaction which leads to diphenylmethane. These product isotope effects are only consistent with the mechanism shown in equation 28 and clearly demonstrate that the radical anion does not decompose by losing nitrogen to form the carbene radical anion when diazoalkanes are reduced. 

Miller and coworkers have used deuterium labelling to study the mechanism of the electrophilic aromatic substitution reactions of jS-aryl-a,jS-unsaturated diazoalkanes. It had been proposed that the reaction proceeded via an Sti electrocyclic ring closure followed by a [1,5] sigmatropic hydrogen shift (equation 36). 

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