Triazolium imides

J(P1)2797>. A similar cycloaddition-rearrangement sequence accounted for the formation of oxazolo[4,5-r/ [l,2,3]tri-azoles 203 as side products from the reaction between triazolium imides 201 and N-substituted benzaldimines, leading to the imidazo[4,5-t/ [l,2,3]triazole 204 (Equation 23) (see Section 10.05.10.3). The oxazolotriazoles 203 were presumed to arise as a consequence of hydrolysis of the imine to the parent aldehydes under the reaction conditions <2003ARK110>. 

The synthesis of a new series of tetrahydro-oxazolo[4,5-d]-1,2,3-triazoles (102) has been reported. The triazolium imide 1,3-dipole (104) reacted with ( )-cinnamaldehyde in refluxing ethyl methyl ketone. It is significant that it was to the C=0 bond of the a,/ -unsaturated aldehyde that the cycloaddition took place, yet analogous addition to benzaldehyde or aliphatic ketones was not possible. The primary products of the cycloaddition reaction (105) underwent a sigmatropic rearrangement to furnish the new ring system (102) as shown in Scheme 23 <90JCS(P1)2527>. 

Treatment of the triazolium imide dipoles 2 with methyl cyanodithioformate in benzene gives, in a particularly facile reaction, the trisubstituted thiatriazines 3 in high yield (Method A).5,8... 

Dihydro-1,2,3,5-tetrazines (13) have been obtained by 1,3-dipolar cycloadditions of A-sul-finylimines with substituted triazolium imides (27), followed by rearrangement and sulfinylimine elimination. When Ar Ar, both expected products (13a) and (13b) were produced (Scheme 4) <88CC232, 90JCS(P1)2527>. 

The nitration of the 2,7-diamino-77/-[l,2,4]triazolo[3,4-c][l,2,4]triazolium ion 44 with nitronium tetrafluoroborate affords after workup with base the corresponding potassium bis(iV-nitro imides) 45 <1991IZV1239>. 

Oxidation of a-diketone hydrazone imines with cuprammonium salts gives 2/f-triazoles. With substituted imines (using W-bromosuccin-imide as oxidant) 1,2-disubstituted triazolium salts are obtained (Scheme 33). ... 

Triazolium-l-imides are in equilibrium with l,2-cis-bis(arylazo)ethenes, which have been investigated by variable-temperature NMR <87JCR(S)332> (see Section 4.01.2.5) and by ab initio calculations <90CC882> (see Section 4.01.1.5). 

The reactions of 1,2,3-triazolium 1-imide (277) with a range of alkene and alkyne dipolarophiles give rise to a variety of new ring systems (Scheme 54). Compounds (276) and (278) are obtained from (277) by reaction with acrylonitrile and DMAD, respectively. These reactions are tandem 1,3-dipolar (endo) cycloadditions and sigmatropic rearrangements which are regio- and stereospecific <90JCS(Pl)2537>. Kinetic and mechanistic studies show that these reactions are dipole-HOMO controlled. The second-order rate constants are insensitive to solvent polarity, the reaction indicates... 

The synthetic applications of substituted 1,2,3-triazole 1-oxides and 1,2,3-triazolium-l-imides in the preparations of 1,2,3-triazines, 1,3,4,5-oxo- and -thia-triazines, and 1,2,3,5-tetrazines have been discussed in Section 4.01.4.12. Conversions of 1,2,3-triazolines into aziridines either thermally or photochemically were described in detail in CHEC-I <84CHEC-1(5)691 > and in a review <84AHC(37)217>. Some recent developments are discussed in Section 4.01.5. 

Likewise, the fused-ring triazoline adducts 112, obtained from 1-methyl-1,2,4-triazolium-4-(acyl)imides and propiolic ester, undergo rupture at the N—N or C—N bond to yield triazole or pyrazole compounds (Scheme 37) (76CPB2568). 

With aromatic isothiocyanates, triazolium-4-(acetyl)imide displays both 1,3- and 1,5-dipolar activity, depending on reaction conditions, mainly solvent polarity. In nonpolar solvents such as benzene, concerted 1,3-additions occur across both the C=N (113) and C=S (114) bonds of the isothiocyanate (84CCC1713) this is unlike the reaction of isothiocyanates with azomethinimines of the dihydroisoquinoline series, in which 1,3-ad-... 

Triaryl-4//-l,3,4,5-oxatriazines, e.g. 3, have been synthesized by two routes, both involving ring expansion of a 1,2,3-triazole. In the preferred method, reaction of a 1,2,3-triazolium A-imide, e.g. 1, with cinnamaldehyde gives a tetrahydrooxazolo[4.5-[Pg.801]

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... 

Aryl-2,5-dihydro-l,2,3-triazines, also with electron-withdrawing substituents, are available via 1,3-dipolar cycloaddition of electron-poor dipolarophiles (DMAD, maleonitrile, etc.) to 1,2,3-triazole 1-oxides <1987CC706, 1990J(P1)3321> or 1,2,3-triazol-l-ium imides (Equations (126) and (127) Section 9.01.10). The electronic properties of the aryl groups introduced with the triazolium precursor may vary widely. If alkenes are used as dipolarophiles, thermolysis of the adducts has to be combined with oxidation by manganese dioxide <1993JCM78>. 

Treatment of the triazolium A -imide 1,3-dipoles 246 with dry hydrogen sulfide in dichloromethane gave high yields of the 2,4,6-triaryl-l,3,4,5-thiatriazines 45 (Scheme 47) <1994JCM350>. 

Oxatria%ines. Acid-catalyzed ring transformation of 4,5-diaryl-l,2,3-triazolium-iV aryl imides (Scheme 47) -good yields of 2,4,6-triarylsubstituted products only. 

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