Cinnamoyl azides Curtius rearrangement

In a related type of reaction, the styryl isocyanates, readily available by Curtius rearrangement of cinnamoyl azides, undergo thermal cyclization to l-isoquinolones in good yield (equation 34) the reaction can also be carrried out using Friedel-Crafts catalysts. 2,3-Dihydro-4( 1//)- isoquinolones are obtained by Dieckmann cyclization of N- (o- carbalkoxy-benzyl)glycine ester derivatives (equation 35). The same reaction has been used for the synthesis of a range of non-aromatic heterocycles (equations 36 and 37). 

Styryl isocyanates 183, readily available by Curtius rearrangement of cinnamoyl azides, undergo thermal or Friedel Crafts cyclization to 1-isoquinolones 184 (Scheme 110). 

The Curtius rearrangements of some franr-cinnamoyl azides (13), obtained by treatment of the corresponding chlorides with sodium azide, smoothly give franr-3-styryl isocyanates (14), which are efficiently isomerized in an inert solvent at 250 °C to produce 1-isoquinolone derivatives (15 equation 9). The isomerization proceeds more conveniently at 140 °C in the presence of iodine. 

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