1-Sulfonyl-l,2,3-triazoles

Trisubstituted 4-oxazolines 155 were efficiently prepared from 1-sulfonyl-l,2,3-triazoles 154 and aldehydes in the presence ofRh(II) catalysts, likely through Rh(II)-azavinyl carbenes I and ylides II as reaction intermediates (13AGE1507). 

SCHEME 5.46 Rh-catalyzed transannulation of 1-sulfonyl-l,2,3-triazoles with nitriles. 

Apart from the utilization of aryl- and vinyl-diazoacetates that can achieve the moderate to high chemo-, regio-, and enantioselectivity in intermolecular asymmetric C—H bond insertion reactions, Af-sulfonyl-l,2,3-triazole 11 was found to be able to function as an alternative carbene precursor for diverse transformations (Scheme 1.4). One advantage for using the N-sulfonyl-1,2,3-triazole is that it could be easily prepared by the Cu -catalyzed azide-alkyne cycloaddition (CuAAC) reaction, and in some cases, delicately designed reactions can be conducted in a one-pot procedure starting from alkynes and sulfonyl azides. Moreover, since there exists an inherent equilibrium... 

Scheme 1.4 Formation of metal-bound imino carbene from iV-sulfonyl-l,2,3-triazole.

The reaction of azides with ethoxyacetylene (98) has been studied by Italian authors. With aliphatic and aromatic azides, the expected 1-substituted 5-ethoxy-l,2,3-triazoles (99) are obtained.310-311 Sulfonyl azides, on the other hand, react with ethoxyacetylene at room temperature to yield no triazoles but the valence tautomeric diazo compounds (100).312-313... 

The amination of 5-phenyl-l,5-dihydro[l,2,3]triazolo[4,5- /]-l,2,3-triazole (31) with o-(mesityl-sulfonyl)hydroxylamine afforded two V-aminated products distinguishable on the basis of their l3C NMR spectra (Equation (1)). The major product (46%), showed one carbon signal other than those from the phenyl ring and was therefore assigned as the symmetrical 2-amino derivative (32). The minor product showed two l3C signals in addition to those from the phenyl ring and was believed to be represented by structure (33) or (34) (33) is the preferred isomer on the basis of the similarity of its NMR spectrum to that of known l-acetyl-5-phenyltriazolotriazole. 

The more general preparations of A-acyltriazoles and A-acylbenzotriazoles have utilized acid chlorides in reactions with 2-trimethylsilyl-l,2,3-triazole, l-(trimethylsilyl)benzotriazole 133 or l-(tributylstannyl)benzotriazole. Thus 133 reacts with phosgene or sulfuryl chloride to give 1,1-carbonyl- 134 and l,l-sulfonyl-di(benzotriazole) 135. Treatment of 134 with an alkanol affords 1-alkoxycarbonylbenzotriazoles 136. 

Polystyrene-sulfonyl hydrazide resins 153 reacted with various amines to give regiospecifically 1,4-disubstituted-l,2,3-triazoles 154 via traceless cleavage reactions <04TL6129>. A library of peptidotriazoles were prepared by solid-phase peptide synthesis combined with a regiospecific copper(I)-catalyzed 1,3-dipolar cycloaddition between resin-bound alkynes and protected amino azides <04JCO312>. 

The cyclocondensation of 3-(2,4-dichlorophenyl)-5-sulfonyl[l,2,4]triazole (345) with chloroacetic acid affords 2-(2,4-dichlorophenyl)-5,6-dihydrothiazolo[3,2-i][l,2,4]-triazol-6-ones (346) (Equation (109)) <9iH(32)23i>. The same reaction in the presence of an aromatic aldehyde gives rise to 6-arylidene-2-(2,4-dichlorophenyl)-5,6-dihydrothiazolo[3,2-6][l,2,4]triazol-6-ones (103) (see Section 8.05.6.2.1) <91H(32)231>. 

Bis-acceptor-substituted diazomethanes are most conveniently prepared by diazo group transfer to CH acidic compounds either with sulfonyl azides under basic conditions [949,950] or with l-alkyl-2-azidopyridinium salts [951] under neutral or acidic conditions [952-954]. Diazo group transfer with both types of reagents usually proceeds in high yield with malonic acid derivatives, 3-keto esters and amides, 1,3-diketones, or p, y-unsaturated carbonyl compounds [955,956]. Cyano-, sulfonyl, or nitrodiazomethanes, which can be unstable or sensitive to bases, can often only be prepared with 2-azidopyridinium salts, which accomplish diazo group transfer under neutral or slightly acidic reaction conditions. Other problematic substrates include amides of the type Z-CHj-CONHR and P-imino esters or the tautomeric 3-amino-2-propenoic esters, which upon diazo group transfer cyclize to 1,2,3-triazoles [957-959]. 

The addition reactions of aryl azides onto enamines bearing a carbonyl, sulfonyl, or nitro group in the 0 position with respect to the nitrogen atom have been investigated by Italian authors.240-241 The expected triazoline derivatives could not be isolated but were immediately converted into the corresponding 1,2,3-triazoles (49) and secondary amines. The reaction of p-nitrophenyl azide with l-benzoyl-2-morpholino-l-propene (48) is given as a typical example. 

It is interesting to note that the bond lengths C-S in two structurally related compounds l-(mesityl-2-sulfonyl)-3-nitro-l,2,4-triazole [120] and l-(mesitylsulfonyl)-4-nitroimidazole [121] are similar (1.761 and 1.758 A), while the S-N bond in imidazole analog is significantly shorter (1.736 and 1.708 A). 

The molecule of 3-nitro-3 -chloro-l//-bi-l,2,4triazole-5,l -yl has transoid conformation, where the substituents (chlorine and nitro group) are most distant from each other and the rotation angle of two triazole rings is 5°, while the nitro group is rotated by 4° with respect to the triazole cycle [156], Molecular and crystalline structures of 1-methyl-3,5-dinitro-l, , 4-triazole [153] and l-(mesityl-2-sulfonyl)-3-nitro-l,2,4-triazole were determined [119]. 

Other methods for the synthesis of l,4-dihydro-l,2,4,5-tetrazines 9 which can be explained by intermediate formation of nitrile imines 8 are the photolysis of 1,2,3-triazoles 2181 and sydnones 3,182 reaction of tetrazoles 4180 with tosyl chloride, elimination of pyridine from the pyridinium compounds 5,189-190 of hydrogen chloride from the hydrazonic acid chlorides 1 s.3-i88 or elimination 0f sulfinate from the a-sulfonyl hydrazone 7.189... 

For the heterocondensation of 2-amino-5-aryl-5/f-thiazolo[4,3-6][l,2,4]oxadiazoles and -thia-diazoles (93) and 5-aryl-2-sulfonyl-l,5-dihydrothiazolo[3,4-Z ][l,2,4]triazoles (95) with formaldehyde and a-amino acids see Section 8.05.6.1.2 <94Mi 805-oi>. 

The reaction of 3-aryl-5-sulfonyl-4//[l,2,4]triazole with phenacyl bromides in methanol gives 3,5-diarylthiazolo[2,3-c][l,2,4]triazoles (46) in one step (see Section 8.05.9.1.11) (Equation (114)) <88CAT91>. 

Contrasting with the reported formation of fused [l,3,4]thiadiazole rings in the course of the reaction of 3-substituted 4-amino-5-sulfonyl-4/f-[l,2,4]triazoles (104) with various isothiocyanates (cf. 8.07.8.3.1, Table 10) there are reports that the reactions with methylisothiocyanate and similarly with phenylisocyanate afford 3,7-disubstituted 6,7-dihydro-5//-[l,2,4]triazolo[4,3-f)][l,2,4]triazole-6-thiones (139) and -triazol-6-ones (140), respectively (Equation (37) and Table 14). 

Dimerization of 2-amino-3,4,6-tri-0-benzyl-2-deoxy-D-glucose with l.l -thionyl-or sulfonyl-di-imidazole gave the fructosazine and bis-tetrahydropyrano-piper-azine derivatives 73 and 74 in a ratio of 1 5, respectively a related compound appeared in Vol. 25, p.l32. The P-carboline derivative 75, isolated as a natural product from a hybrid plant cell culture product, was synthesized in six steps from tryptamine and ( )-4,5,6-tri-0-acetyl-2,3-dideoxy-D-ery/Aro-hex-2-enose. Thiazolo-triazoles such as 76, termed acyclo-C-nucleosides, were obtained on deacetylation of the product from condensation of peracetylated D-gluconic or galactaric acids with 4-araino-3-aryl-l,2,4-triazole-5-thiols in the presence of POCls. The related 1,2,4-triazole 77 and dihydroimidazole 78 were obtained by condensation of D-glucono-1,5-lactone with aminoguanidine and ethylenedia-mine, respectively, followed by acetylation then O-deacetylation. ... 

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