Phenyl compounds, azide 1,3-dipolar

Compound 156 (prepared by reaction of tetrabromocyclopropene and 2,5-dimethylfuran) underwent dipolar cycloaddition with phenyl azide to produce the fused triazole 157. The reaction was carried out in dichloromethane at room temperature over 2 days. This lower reaction temperature allowed for the isolation of the adduct 157, which was established by X-ray crystallographic analysis to be the product of ct>-selective addition. Heating triazole 157 in benzene at reflux for 2 h resulted in ring expansion producing a 1 1 mixture of compounds 158 and 159 (Scheme 16) <2004JOC570>. 

The 1,3-dipolar addition of secondary diazo-compounds to 1,3,3-trimethylcyclo-propene affords 2,3-diazabicyclo[3,l,0]hex-3-enes [cf. (130)], but with diazoacetic ester this product, with an acidic proton at C-4, undergoes rearrangement to ethyl 3,4,4-trimethyl-l,4-dihydropyridazine-6-carboxylate. Further additions of phenyl azide to methylenecyclopropanes have shown that the presence of a carboxylate group in the three-membered ring causes the initially formed spirodihydrotriazole to undergo rearrangement to a 4-substituted 1,2,3-triazole. ... 

The relative reaction rates of the 1,3-dipolar cycloaddition reaction of phenyl azide to dipolarophiles containing the C=C bond can be predicted by using the Jaguar V. 3.0 ab initio electronic package. Thermodynamic analysis of the 1,3-dipolar cycloaddition of organic azides with conjugated nitroalkenes at 273-398 K shows that temperature does not affect the course of these reactions in the vapour phase. Density-functional procedures have been used to explain the regioselectivity displayed by the 1,3-dipolar cycloaddition of azides with substituted ethylenes. A density-functional theory study of the 1,3-dipolar cycloaddition of thionitroso compounds with fulminic acid and simple azides indicates that the additions are not stereospeciflc. ... 

A widely used method of the preparation of versatile 1,2,3-triazoles and tetrazoles consists in the reaction of azides with fluorine-containing compounds with multiple bonds. For example, this approach afforded N-substituted 4(5)-fluoro-l,2,3-triazoles 27,28 by the 1,3-dipolar cycloaddition of perfluoropropadiene to phenyl azide [35], In the course of the reaction a mixture of regioisomeric 1,2,3-triazoles was formed l-phenyl-4-fluoro-5-trifluoromethyl-l,2,3-triazole 27 was considerably prevailed. On the contrary, the reaction of phenyl azide with the perfluoropropyne resulted in predominantly the isomer that was minor in the previous scheme. 

---