Azidohydrin intermediates

A further advantage of this protocol is that it allows the azidohydrin intermediate to be isolated. This will facilitate important mechanistic work to clarify the nature of the reactive species responsible for the ring expansion. Although only the preparation of azepin-2-... 

The reaction with a ketone gives an azidohydrin intermediate, which rearranges to form an amide ... 

In some cases the ring expansion involves the rearrangement of an azidohydrin intermediate (equation l). 

Reaction of ketones with hydrazoic acid gives azidohydrin intermediates, which undergo rearrangement to form amides. ... 

An example of ring enlargement is the intramolecular Schmidt reaction of azidoalkyl ketone 53 that gives, by the action of titanium tetrachloride, through intermediate azidohydrin, lactam 20 (95JA10449). Because of the large distance between keto and azido groups, the usual catalyst trifluoroacetic acid does not work. 

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