Allyl azides, isomerisation

The rearrangement of ally ethers is not without its complications. For example, with less active catalysts that require elevated temperatures, adjacent azides can undergo [3+2]-cycloaddition on the alkene of the allyl ether function before isomerisation occurs [Scheme 4.220), but this can be avoided by using a more active iridium catalyst that isomerises the alkene at room temperature. Iridium catalysts are also preferred over Rh owing to problems of competing reduction of the alkene which can occur with the latter (see above). 

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