1 -Benzyl-4-phenyl-1,2,3-triazole

Iminomethyl-l-phenyl-l,2,3-triazoles (106, R = CH3) and their structural isomer 4-(iminophenyl)-l-methyl-l,2,3-triazole (108, R = CH3) are interconvertible when they are heated in DMSO at 80°C (Scheme IV.43) (84JHC627 89JHC701 90JHC2021). The equihbrium position is dependent on the electronic properties of the substituent R. When R is alkyl, a benzyl or anisyl compound 108 is favored when R is p-chlorophenyl or p-nitrophenyl, 106 is the favored isomer. The hydrazone 106 R = NH2) or oxime 106 R = OH) do not rearrange. A diazoimine 107 can be postulated as intermediate, a species whose structure is similar to the one proposed... 

Substituted 1,2,4-triazoles have received less attention than their isomeric counterparts, but those results that are available indicate that their lithio derivatives are less stable than their 1-substituted isomers. Thus, in addition to undergoing the expected a-lithiation and reaction at the 5-position, 3-phenyl-4-benzyl-1.2.4-triazole also gave products resulting from ring-opening, even at -78°C (Scheme 65) (86JHC1257). 

Triazoles can be activated towards electrophiles by the introduction of an A-oxide group. N-Oxidation gives rise to better activation of the 5-position than the 4-position. Thus, bromination of 3-benzyl-1,2,3-triazole 1-oxide (192, R = PhCH2) requires only 120 h at 20 °C and affords the 5-bromo compound (193) in quantitative yield <87ACS(B)724>. 3-Phenyl-1,2,3-triazole 1-oxide is... 

Cycloaddition of p-methoxyphenyl azide to alkynic dipolarophiles at room temperature gives triazoles (697) and (698) (Equation (54)). A regiospecific addition is only observed in the case of Z = CH(OMe)2 <89H(29)967>. Phenyl azide and substituted benzyl azides undergo 1,3-dipolar cycloadditions with DM AD, phenylacetylene, and ethyl propiolate to afford 1-phenyl- and 1-benzyl-... 

The oxide group mildly activates 3-substituted 1,2,3-triazole 1-oxides to electrophilic attack. Thus, 3-benzyl-1,2,3-triazole 1-oxide reacted much more rapidly than the unoxidized compound in giving the 5-bromo derivative, and there have been a number of other examples of 5-bromination and 5-chlorination of triazole oxides, including that of the 3-phenyl-l-oxide, which was not para-halogenated [87ACS(B)724]. 

Benzylsulfanyl-5-phenyl-[l,2,4]triazol-4-ylmethyl)-benzamide (33). A solution of 4-(3-mercapto-5-phenyl-[l,2,4]triazol-4-ylmethyl)-ben-zamide (32, 0.1 mmol) in THF (6 ml) was treated with Amberlite resin (OH form, 0.1 mmol OH ) and benzyl bromide (0.15 mmol). The resulting mixture was shaken at room temperature until complete consumption... 

The l,4-diacyl-3-acylamino-5-phenyl-4,5-dihydro-1H-1,2,4-triazole (99) was generated by the ring-closure of a guanidinylhydrazone with acetic anhydride in ca. 80% yield. The structure of the triazole was confirmed by spectroscopy and x-ray analysis [95M733], The N-benzyl triazoline (100) was prepared by reaction of N-benzylidinebenzylamine with a hydrazonyl halide with K,CO, in benzene, followed by 2 eq of Et,N for 1 h, in 75% yield [95ZOB308]. 

Preparation of 5-(3-(2-(5-methyl-2-phenyl-oxazol-4-yl)ethoxy)benzyl)-2-phenyl-4-A-phenylamido-l, 2,3-triazole... 

The cycloaddition of 4-phenyl-3//-l,2,4-triazole-3,5(47/)-dione and 4-benzyl-3,4,5-trimethyl-pyrazole gives an approximately 1 1 mixture of diastereomeric products 7, which can be separated by crystallization and decomposed separately photochemically to 1,5,7-triazatricy-clo[3-3.0.02,4]octane-6,8-diones 861. 

Only the bisadduct 11 is obtained by reaction of 4-phenyl-37/-l,2,4-triazole-3,5(4//)-dione with 7b-methyl-7b//-cyclopent[cc/]indene10. Whereas the first molecule of triazoledione undergoes addition anti to the methyl substituent for steric reasons, the direction of approach of the second triazoledione molecule can also be controlled by secondary orbital interactions between the incoming dienophile and the triazolidinedione unit in the 1 1 adduct. The cycloadduct cannot be obtained from the 7-benzyl derivative, due to a rearrangement of the substrate11. 

Figure 4 Some parameters of structure determinations of (a) l,3-dimethyl-4-(l,2,3-triazolio)sulflde (10) (75ACsiA)647> (b) l-phenyl-3-methyl-4-(l,2,3-triazolio)sulflde (11) (79ACS(A)687) (c) l-methyl-3-phenyl-4-(l,2,3-triazolio)sulflde (12, 13) (79ACS(A)687> (d) l-methyl-3-benzyl-4-(l,2,3-triazolio)sulflde (14) (79ACS(A)693> (e) 2,3-dimethyl-l,2,3-triazol-l-ine-4-thione (15) (79ACS(A)697) (f) 2-phenyl-3-methyl-l,2,3-triazol-l-ine-4-thione (16) (79ACSIA)697)...

In some cases the observed alkylation on N-4 does not lessen the validity of the generalization that suggests preference for N-1. Thus 3-phenyl-5-ureido-1,2,4-triazole (55) is methylated or benzylated to give (56 Scheme 20) because the internal hydrogen bridge preempts the favoured N-1 site. 

A variety of l-benzyl-[l,2,3]triazolo[4,5- >]pyrazines has been prepared by the condensation between a-dicarbonyl compounds and 4,5-diamino-l-benzyl-l,2,3-triazole (Scheme 64) (72JOC4124). 2-Phenyl derivatives have been synthesized in a similar way using 4,5-diamino-2-phenyl-l,2,3-triazole (Scheme 64) (78JOC341). 

When 4-amino-3-benzyl-l,2,3-triazole-5-carbonitrile was refluxed with ethanolic potassium hydroxide, the dimer 91a was isolated in 40% yield. A similar dimer (91b) was produced by the action of phenyl azide on malono-nitrile. ... 

---