Azides rearrangement

Cyclobutanecarboxylic acid azides react in a similar manner. The azides were either made from the acid chloride and sodium azide44,45 or directly from the acid by reaction with diphenylphos-phoryl azide.37,46,47 The carboxylic acid azides rearrange via the isocyanates. An example is the reaction of (+ )-ra-2-acetoxycyclobutanecarboxylic acid with diphenylphosphoryl azide to give 4 in quantitative yield.37... 

The application of the procedure to azides containing other functional groups has also been described. Diamines (from dicarboxylic acids), arylha loamines, and nitroarylamines have been successfully prepared, whereas certain groups like the double bond, hydroxyl, carbonyl, and amino often cause the formation of products other than the anticipated amine. For the synthesis of a-amino acids, the readily accessible alkylcyanoacetic esters may be employed as starting materials. Their azides rearrange to cyano isocyanates, which can be easily hydrolyzed. ... 

Cyanogen bromide, triazine method, cychc trani-2,3-carbonate reaction, carbonylation, periodate oxidation, epoxide activation Curtis azide rearrangement, coupling reagent method, acid anhydride reaction Schiff base formation reaction... 

Even if no nitrenes are produced as intermediates, the isocyanates formed in Curtius-type rearrangements are of value for the synthesis of heterocyclic compounds. For example, transient isocyanates cyclize unto azine rings, giving imidazoazines (Scheme 21).161 N,N-Diphenylcarbamoyl azide rearranges thermally to 1-phenylindazolone (Eq. 35) via the elusive diphenyla-mino isocyanate.162 Further examples have been summarized by Reichen.163... 

There is strong evidence that alkyl azides rearrange to imines via nitrenes thermally, but that the photochemical reaction is a nonnitrene process (Eq. 

Phosphinimines obtained from 1,2-trans 6-0-/ -tolylsulfonylhexopyranosyl azides rearrange to 6-amino-l,6-anhydro-6-deoxyhexoses, which are stable as acylated derivatives. As intermediates, the tosylate salts could be... 

Azide rearrangements in electron-deficient systems (particularly, Schmidt lactam synthesis) 06CSR146. 

Carboxyl Poly(acrylic acid), poly(glutamic acid), CM-cellulose, poly(acryl amide) Curtis azide rearrangement, coupling reagents method, acid anhydride reaction [182-185]... 

CHAPTER 4 ALKYL AND ACYL AZIDE REARRANGEMENTS Scheme 4.1 Schmidt reaction. 

Aldehydes can also be precursors for the Curtius acyl azide rearrangement tScheme 4.24) Aliphatic and aromatic aldehydes can be converted to the corresponding acyl azides by treatment with iodine azide. Subsequent heating gave various carbamoyl azides in high yields. A radical pathway, proceeding by homolysis of the iodine-azide bond, was proposed. The resulting carbamoyl azides 65 are relevant precursors for the synthesis of amines or ureas, for example. 

The Schmidt reaction of carboxylic acids proceeds via acylium ion, which undergoes addition with hydrazoic acid to generate acyl azide. This azide rearranges with loss of nitrogen to give isocyanate, which leads to an amine upon hydrolysis." ... 

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