Carboxylic acid azides amines

Carboxylic acid azides give rise to three different reactions under different conditions. Azide coupling (equation 9) was the earliest method in peptide synthesis and is still one of the most important in fragment condensation and preparation of cyclic peptides due to its almost complete lack of racemization. At elevated temperatures a frequent side reaction is the Curtius rearrangement. Trapping of the intermediate isocyanate with amines (equation 10) gives urea derivatives and with carboxylic acids rearranged amides are obtained (equation 11). ... 

Amines from carboxylic acid azides CONs —> NHg... 

Reduction of aldehydes and ketones allylic alcohols from a, 3-unsaturated aldehydes and ketones alcohols from carboxylic acid chlorides amines from aliphatic azides.21 ... 

In hot ethanol, benzoyl azide was converted to ethyl A-phenylcarbamate (1894). This Curtius rearrangement was recognized by its discoverer as a general method of degrading carboxylic acids to amines, whereas the intermediacy of isocyanates escaped him. 

Amines from carboxylic acid chlorides via carboxylic acid azides Shortened Curtins degradation... 

Carboxylic acid derivatives can be converted into primary amines with loss of one carbon atom by both the Hofmann rearrangement and tire Curtius rearrangement. Although the Hofmann rearrangement involves a primary-amide and the Curtius rearrangement involves an acyl azide, both proceed through similar mechanisms. 

Carboxylic acids can also be activated by the formation of mixed anhydrides with various phosphoric acid derivatives. Diphenyl phosphoryl azide, for example, is an effective reagent for conversion of amines to amides.140 The proposed mechanism involves formation of the acyl azide as a reactive intermediate. 

The carboxylic acid group is converted by CDI and sodium azide into an acid azide, which via a Curtius rearrangement gives the corresponding amine.[135a3... 

Curtius reaction org chem A laboratory method for degrading a carboxylic acid to a primary amine by converting the acid to an acyl azide to give products which can be hydrolyzed to amines. kard e as re,ak-shan cyanaicohoi See cyanohydrin.. sT an al ka.hol ... 

Employing iminophosphoranes to protect a group labile under alkaline conditions can lead to a dramatic increase in yield. This is exemplified by the transformation of allylic azide 31 into the corresponding iminophos-phorane 32 shown in Scheme 16. Hydrolysis under basic conditions leads finally to 4-amino-3-hydroxycyclohexa-l,5-diene-l-carboxyclic acid (33) in 80% yield. However, when the same azide (31) is converted with a Lindlar catalyst, via allylic amine 34 into carboxylic acid 33, only 0-30% yields are found as a consequence of the low stability of the allylic amine [93JCR(S)148]. 

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