Photochemistry of Acylazides V. Sensitization of decomposition of p‐trimethylsilylbenzoylazide (TSBA)

The sensitized decomposition of p-trimethylsilylbenzoylazide by aromatic ketones benzophenone, thioxanthone and 4,4′-bis(dimethylamino)benzophenone (Michler's ketone) and by diphenylanthracene and pyrene was investigated. Excited benzophenone acts as producer of solvent radicals which attack the TSBA forming the substituted benzamide. Only short chain lengths are observed in the case of cyclohexane as solvent. Michler's ketone, diphenylanthracene and pyrene sensitize the decomposition of TSBA via electron transfer processes forming the substituted phenylisocyanate beside primary and secondary amides. The product ratio is dependent on the solvent properties. Reaction mechanisms are proposed which are founded on time resolved and stationary measurements of transient intermediates and quantum yields.