Curtius reaction, modification using

Curtius reaction, modification using mixed carboxylic-... 

This modification of the Curtius reaction has been used extensively in many laboratories and has been found to be generally applicable. Some examples from the literature include the stereoselective synthesis of a wide variety of cyclopropylamine derivatives from the corresponding acids,11-13 the stereoselective preparation of some substituted norbornylamines from easily isomerized acids,14 the preparation of some 1-aminocyelobutancearboxylic acids from the corresponding acid esters,18 the preparation of a substituted cyclobutanone from... 

The Schmidt reaction cannot be used on acids unstable towards sulfuric acid or on acids containing aromatic rings that are readily sul-fonated. The Curtius reaction can be used on such compounds in one of its modifications (see p. 339), in which an acid chloride is treated with sodium azide in boiling benzene and thus transformed directly to the amine, " it is almost as direct as the Schmidt process. 

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