Pyrolysis, acyl azides

The Curtius rearrangement involves the pyrolysis of acyl azides to yield isocy-anates. " The reaction gives good yields of isocyanates, since no water is present to... 

Nitration of various phenyl-49 and benzyl-phosphine60 oxides (59) has been described, and the P=0 group found to be mem-directing49 in the former case. Pyrolysis of the acyl azide (60)51 takes the course shown. 

Photolysis of alkyl azides bearing pendant aryl groups does not lead to intramolecular trapping of a nitrene by the aryl group. However, intramolecular capture of the putative nitrene is observed upon pyrolysis of the azide precursor. These observations convinced Kyba and Abramovitch" ° that 1,2-migration is concerted with loss of nitrogen from the excited state of the azide, but that a free singlet nitrene is formed upon thermal decomposition. The chemistry of acyl azides will be shown later to exhibit the opposite pattern. 

There are a multitude of variations on the basic Hofmann rearrangement. The simplest is the pyrolysis of acyl azides to isocyanates, which only involves the central rearrangement step. Write down the pathway for this reaction. 

The Curtius rearrangement involves pyrolysis of an acyl azide that expels molecular nitrogen and at the same time rearranges to an isocyanate (the azides... 

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