Azide, ammonia surrogate

Azide is a reactive nucleophile and is used as an ammonia surrogate. Desym-metrization of the dicarbonate 229 occurred by the reaction with TMS azide to afford azide 230 in 82 % yield with higher than 95 % ee. The reaction is a key step in the asymmetric total synthesis of (+)-pancratistatin [83]. 

The utilization of in sim generated aryl azides is not restrictive to [3+2] Huisgen condensation-type reactions. These compounds could also play the role of ammonia surrogate for the synthesis of aniline derivatives. Thus in 2004 Fu, Qiao and co-workers described conditimis involving Cul with or without DMEDA L26... 

Azide is widely useful as a surrogate for ammonia in nucleophilic substitution reactions, due to its high nucleophilicity, low basicity, and stability towards a variety of conditions for subsequent transformations. In particular, the azidolysis of... 

This is clearly a much longer sequence to make a primary amine than simple reaction with ammonia. It does not suffer from problems of polyalkylation, however, and the yield of the amine for the two-step sequence is often higher than the direct reaction with an amine. The fact that this procedime is used more often to make aliphatic primary amines than the reaction of ammonia with an alkyl halide suggests the severity of the problems associated with polyalkylation. The preparation of secondary or tertiary amines often requires the use of the S- 2 reaction with amines, however. Other amine surrogates are known, including the azide ion (Section 11.3.4) and the cyanide ion (Section 11.3.5), but both give primary amines as the end product. 

As discussed earlier in this chapter, ammonia is not always the best reagent to generate amines from halides. Amine surrogates such as azides or phthalimide usually give better yields in Si,f2-type reactions, although their... 

Other authors presented methods based on surrogates of ammonia such as amidine hydrochlorides [241], 2,2,2-trifluoroacetamides [156], benzophenone imine [242] and sodium azide (cf. Sect. 2.4.1) [243-248]. Although efficient, these systems require an additional deprotection step to get anilines and sometimes the use of stoichiometric amounts of a copper precursor. 

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