Tetrazole 1-substituted, halogenation

Halogen atoms at the tetrazole-5-position are readily displaced by better nucleophiles because of the electron-depleted character of the ring. The nucleophilic displacement was much more rapid with l-substituted-5-bromotetrazoles than with the 2-substituted isomers <84CHEC-I(5)791>. These reactions are often best carried out by warming the halotetrazole in the neat amine or hydrazine when these are liquid. Synthetic uses of the reaction are shown in Schemes 6 and 10. New routes to 5-halotetrazole derivatives have been found <95J06468>... 

Nucleophilic substitution of the terminal halogen in the alkyl groups at G-5 atom is a simple but efficient approach to modification of tetrazole derivatives. Treatment of 1-phenyl-5-chloromethyltetrazole with imidazole or pyrazole (DMSO, NaOH) gave the corresponding products of the halogen /3-substitution 338 and 339 <2002JOC8230>. 

Growing attention is directed to intramolecular reactions involving alkyls attached to position 5 of the tetrazole ring. The synthesis of 4,5-dihydrotetrazolo[l,5- ]quinoxalines 347 from 5-substituted tetrazoles 346 via the intramolecular. KNAr substitution of the halogen in the ortho-position of the iV1-aryl substituent is an example of such a reaction (Equation 64) <2006TL2041>. 

The substitution of the halogen in the cyclic imidoyl chloride, like 2-chloropyridine, with azide leads to the intermediate formation of an imidoyl azide 497 that further undergoes cyclization into a fused tetrazole 14 (Scheme 61) <2004SOS(13)861>. 

Electroreduction of l-(4-fluorophenyl)-5-(2-halogenophenyl)tetrazoles (89), when the halogen substituent is Cl, Br or I, leads to cleavage of the carbon-halogen bond to give a phenyl radical (equation 52). Competition then follows between intramolecular radical substitution giving 7-fluorotetrazolo[l,5-f]phenanthridine (90). Further reduction of the... 

Substituted tetrazoles 40 (X = halogen, N3, NHj, OH) liberate nitrogen on heating at 110-200 °C without solvent, or in an aromatic solvent, and furnish acetylenes in 16-81% yields, depending on and R (equation 118). A FBW-type of rearrangement might be involved. ... 

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