Azido leaving groups

Introduction of the azido group into the azine heterocycle can also be accomplished starting with azine derivatives bearing a five-membered heterocycle as a leaving group in this position. Table 8 shows three such conversions where the leaving groups are isoxazolone (entry a), imidazole (entry b), and triazole (entry c) substituents. 

Fluorine and chlorine are the only important choices for the labile substituents on a heterocyclic reactive system but numerous other leaving groups have been patented, mostly as substituent on an s-triazine ring. These include sulpho, cyano, thiocyanato, azido and trichloromethyl [26], as well as more elaborate groupings (Figure 7.2). Such derivatives are... 

Azide ion is a modest leaving group in An + Dn nucleophilic substitution reactions, and at the same time a potent nucleophile for addition to the carbocation reaction intermediate. Consequently, ring-substituted benzaldehyde g m-diazides (X-2-N3) undergo solvolysis in water in reactions that are subject to strong common-ion inhibition by added azide ion from reversible trapping of an o -azido carbocation intermediate (X-2 ) by diffusion controlled addition of azide anion (Scheme... 

Alkyl azides are conveniently prepared from the reaction of alkali metal azides with an alkyl halide, tosylate, mesylate, nitrate ester or any other alkyl derivative containing a good leaving group. Reactions usually work well for primary and secondary alkyl substrates and are best conducted in polar aprotic solvents like DMF and DMSO. The synthesis and chemistry of azido compounds is the subject of a functional group series. ... 

The conversion of 3-amino-3-deoxy sugars into pyrrolidines requires the presence of a leaving group, such as a p-tolylsulfonyloxy group on C-6 this is exemplified by the conversion of 3-azido-3-deoxy-l,2-0-isopropylidene-6-0-p-tolylsulfonyl-a-D-glucofuranose (44) and methyl 3-azido-2-benzamido-2,3-dideoxy-6-0-p-tolylsulfo-nyl-j8-D-glucopyranoside (46) into the respective pyrrolidines, 45 and 47, by reduction of the azido group, followed by cyclization.37... 

Alkyl azides can be prepared by treatment of the appropriate halide with azide ion.939 Phase transfer catalysis940 and ultrasound941 have been used. Other leaving groups have also been used,942 for example, OH,943 OMs, OTs,944 and OAc.945 Epoxides react with NaN3, with HN3 in DMF,94 or with HN3-Et3Al947 to give 3-azido alcohols these are easily converted to aziridines,948 e.g.,... 

The azido hgand is particularly versatile as a leaving group, as the displacement is acid catalyzed. Coordinated azide ligands also have the potential to react via 1,3-dipolar cycloaddition with organic isonitriles or nitriles to give 1- or... 

Substantial accelerations have been observed for aquation of halo-, thiocyanato-, azido-, and diacido-metal complexes, particularly in the presence of aqua metal ions such as Hg and Ag+ (17,20, 56, 77, 221, 286). Both the leaving groups themselves and their complexes form strong associations with such added metal ions. For associations such as that in Eq. (13), the equilibrium constant can be readily measured spectrophotometrically (171). 

A selective procedure for the reduction of substituent azido groups (available by displacement of leaving groups by azide anion) to amino groups, without concomitant reduction of other reducible groups. Involves an aza-... 

---