1.4- Dimethyl-1,2,4-triazolium iodide

Dimethyl-1,2,4-triazolium iodide with nickel(II) acetate gives the carbene complex l2Ni( 1,4-dimethyl-l,2,4-triazol-5-ylidene)2 (97OM2209). 

Dimethyl-1,2,4-triazolium iodide with palladium acetate yields the carbene adduct 182 (97JOM(530)259). Under water it undergoes cis-trans isomerization to 183. Some other derivatives were reported in 1981 (81BCSJ800). 1,1 -Methylenebis(4-alkyl-l,2,4-triazolium)diiodides (alkyl = /-Pr, n-Bu, octyl) with palladium(II) acetate give the mononuclear complexes [L Pdl ] (99EJIC1965), where L2= l,l -methylenebis(4-R-l,2,4-triazol-2-ylidene) (R = /-Pr, n-Bu, octyl). Thermolysis of the products in THF gives the rran -dinuclear complexes 184... 

Triazolium salts (335) are not readily reduced by NBH. Indeed, 4-phenyl- and 4,5-diphenyl-1,3-dimethyl-1,2,3-triazolium iodides do not undergo reduction, yet l-methyl-2-phenyl-l,2,3-triazolium triflate (336) is reduced to the 4-triazoline 337. This reactivity pattern is explained by the need for an immonium ion for successful reaction. The presence of a C-2 substituent in 336 makes this possible the lack of such a substituent localizes the double bond joining C-4 and C-5. 

Syntheses of quaternary l-alkyl-3-perfluoroalkyl-4,5-dimethyl-l,2,4-triazolium iodides have led to the disclosure of a variety of new quaternary salts <04JOC1397>. Arylation of 3-alkylthio-5-aryl-l,2,4-triazoles under basic conditions gave 5-alkylthio-l,3-diaryl-l,2,4-triazoles in moderate yields <04JHC201>. Acyl hydrazides 155 reacted with imidates 156 to yield 1,2,4-triazoles 157 followed by Mitsunobu reactions with amino alcohols 158 to give regioisomeric... 

A representative example of the use of triazole reagents as organocatalysts in synthetic transformations [519] is the oxidation of allylic, propargyHc, and benzyhc alcohols to the corresponding carboxylic esters by Mn02 in alcohol solvents, which is mediated by l,4-dimethyl-l,2,4-triazolium iodide (30) in the presence of DBU as a base [520], for example ... 

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