Aliphatic and alicyclic azides

Synthesis of Azides by Nucleophilic Substitution I. Aliphatic and alicyclic azides 

The direct introduction of the azido group by nucleophilic displacement with azide ion constitutes the most convenient and general synthesis of aliphatic azides. Consequently the method has been extensively employed since its first application was reported in 1901 by Curtius . 

Prior to the use of dipolar aprotic solvents for these reactions the general procedure involved interaction of the alkyl substrate with 

As expected, substitution by azide ion occurs more readily when the alkyl substrate bears electron-withdrawing groups. For example phenacyl bromide and its derivatives give high yields of azides when treated with sodium azide in the cold °. Secondary alkyl substrates undergo Sj,2 reactions with azide ion ° ° but with less facility than primary alkyl substrates in accordance with the normal polar influences and primary steric eflfects in reactions . Selective substitution is therefore possible and this has been effectively applied in carbohydrate and steroid synthesis (sections II.B.5,6). These effects are also exemplified in the alicyclic series where it has been reported that menthyl halides and 2-methylcyclohexyl halides afford unsatisfactory yields of azide ° . The unsubstituted alicyclic azides, however, are obtained in good yields by the procedures outlined above(Table 1). 

Extension of the general synthetic method to the synthesis of vicinaD° and geminaD diazides and a,o)-diazidoparaffins ° is well documented. Some diazido compounds have received consideration as explosives and initiators . 

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