1.2.5- Oxadiazole. 4-amino-3-azido

Oxadiazol 2-Azido-5-[(benzyl-oxycarbonyl-amino)-methyl]-E8c, 602 (S02-R - N3)... 

Diazotization of 4-amino-l,2,5-oxadiazole-3-carbohydroximoyl chloride 132 gives 4-[chloro(hydroxyimino)-methyl]-l,2,5-oxadiazole-3-diazonium salt 133 (Scheme 35). Treatment of the latter with NaN3 afforded 4-azido-l,2,5-oxadiazole-3-carbohydroximoyl chloride 134 and the reaction with NaN02 yielded 2-cyano-2-hydro-xyiminoaceto-hydroximoyl chloride 135. By oxidation of 4-amino-l,2,5-oxadiazole-3-carbohydroximoyl azide 136... 

The 1,3-dipolar cycloaddition of azido-l,2,5-oxadiazoles (azidofurazans) to dicarbonyl compounds has been studied and a new procedure for the synthesis of (l,2,3-triazol-l-yl)-l,2,5-oxadiazoles was proposed <2002MC159>. The cycloaddition of 4-amino-3-azido-l,2,5-oxadiazole 168 to nitriles with activated methylene groups has been studied, and 3-amino-4-(5-amino-l/7-l,2,3-triazol-l-yl)-l,2,5-oxadiazoles 169 and the products of their Dimroth rearrangement 170 have been synthesized <2004MC76>. 

Diazotization and nitration provide a synthetic approach to furazan azides and nitroamino derivatives. For example, 3,6-bis(4-amino-l,2,5-oxadiazol-3-yl)-l,4,2,5-dioxadiazine 172 gave 3,6-bis(4-azido-l,2,5-oxadiazol-3-yl)-l,4,2,5-... 

Azido derivatives of furazans have proved to be particularly useful for the synthesis of heterocyclic systems. Thus, by 1,3-dipolar addition of l-azido(4-amino-l,2,5-oxadiazol-3-yl)aldoxime 186 to propargyl alcohol and phenylacetyl-ene, bicyclic 4-amino-l,2,5-oxadiazol-3-yl(4-R-l,2,3-triazol-l-yl)ketoximes 187 were obtained (Equation 34) which in reaction with acetic anhydride afforded the corresponding 0-acyl derivatives <2003RJ0574>. 

The 1,3-dipolar cycloaddition of azidofurazans to acetylenes afforded 1,2,3-triazoles linked with furazan cycle <2000CHE91>. Treatment of 3-azido-2-amino-l,2,5-oxadiazole 194 with ethyl 4-chloroacetoacetate gives access to the functionalized [l,2,3]-triazoles 195, which are good precursors for GSK-3 inhibitors with favorable water solubility (Equation 38) <2003JME3333>. 

Oxadiazoles. Mesitonitrile oxide adds j A -dicyanomethylamine, MeN-(CN)2, to yield the oxadiazole (471 Ar = 2,4,6-Me3C6H2). The action of hydroxylamine on the cyanoimino-ether ArCH2C(OEt)=NCN (Ar = 2,6-CI2C6H3) unexpectedly leads to the 3-amino-oxadiazole (472). 3-Azido-... 

Oxetane 8-amino acids and their 5-azido ester precursors have been submitted to a number of transformations, showing the synthetic potential of these stmctures. 1,2,4-Oxadiazole, commonly used as bioisosteric replacement for amides, esters, and isothioureas [38] was introduced into stmctures type 103 [39] (Scheme 4.16). 

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