1.2.3- Triazole 1-oxide, 2-phenyl-, reaction

A related triazole synthesis utilizes phosphorous ylids, such as 264. The initially formed triazenes cyclize with elimination of triphenylphosphine oxide. The reaction proceeded sluggishly with phenyl azide, but good results have been obtained with acyl or sulphonyl azides. Tosyl azide and 264 yielded 98% of the 1-tosyl-triazole 265. The tosyl group could be removed by solvolysis in boiling ethanol... 

There are several reports on conversion of 1,2,4-triazines into 1,2,3-triazole derivatives (66JOC3914 76LA153 78HC(33)189). Acidic hydrolysis of 3-methyl-6-phenyl-l,2,4-triazine 4-oxide (160) affords 4-phenyl-1,2,3-triazole (162). The reaction occurs via an ANRORC route initiated... 

Oxidation of the hydrazone of 2-hydrazinopyrazole (226) with Pb(OAc)4 in CH2CI2 is a two-step reaction. The azine (227) was formed as an intermediate and this underwent ring closure to the 3H-pyrazolo[5,l-c][l,2,4]triazole (228) (79TL1567). A similar reaction applied to the benzal derivative of 2-hydrazinobenzothiazole (229) gave 3-phenyl-[l,2,4]triazolo[3,4-6]benzothiazole (230) together with a by-product (231) (72JCS(P1)1519). 

Since both oxepin and its valence isomer benzene oxide contain a x-tb-diene structure they are prone to Diels-Alder addition reactions. The dienophiles 4-phenyl- and 4-methyl-4//-l,2,4-triazole-3,5-dione react with substituted oxepins at room temperature to give the 1 1 adducts 7 formed by addition to the diene structure of the respective benzene oxide.149 190,222... 

In the presence of various metal ions, 2-(fluoroenone)benzothiazoline has been found to rearrange to A-2-mercaptophenylenimine, while a free radical mechanism involving the homolysis of C-S and C-N bonds has been invoked to explain the formation of 3-phenyl-1,2,4-triazole derivatives from the thermal fragmentation and rearrangement of 2-(arylidenehydrazino)-4-(5//)-thiazolone derivatives. The cycloadducts (36) formed from the reaction of 3-diethylamino-4-(4-methoxyphenyl)-5-vinyl-isothiazole 1,1-dioxide (34) with nitric oxides or miinchnones (35) have been found to undergo pyrolytic transformation into a, jS-unsaturated nitriles (38) by way of pyrrole-isothiazoline 1,1-dioxide intermediates (37). 

Disubstituted 2-phenyl-277-1,2,3-triazole-1-oxides (150) can be easily obtained from the corresponding bis(hydroxyimino)butanes 148 in three steps. Thus, treatment of dioximes 148 with diluted HCl in dioxane with subsequent interaction with PhNHNH2/EtOH/AcOH afforded a-hydrazinooximes 149 in excellent yields. Reaction of 149 with A-iodosuccinimide (NIS) in CCI4 or with CUSO4 in aqueous pyridine afforded triazoles 150 (equation 65) . Similar cyclization in the presence of SOCI2 also leads to... 

The simple sulfur derivatives of triazoles exist as thiones <71JCS(C)1016) but behave as thiols in most of their reactions. The 3-thione derivative (90) reacts with chloropropylene oxide (91) at the least hindered oxide centre to give (92) (Equation (32)) <87CHE228>. 3-Phenyl-5-triazolinethione (93) reacts with (91) to give the cyclic derivative (94), presumably through subsequent nucleophilic displacement of chloride by N(l) (Equation (33)) <90JOU1525>. 

Reaction of a-hydrazinoheterocycles with 4-(hydroxymethylene)-2-phenyl-5(4//)-oxazolone 406 gives rise to A-benzoyl-ot-(heteroaryl)glycinates 563 containing a fused 1,2,4-triazole after oxidative cyclization (Scheme 7.178). ... 

Treatment of verdazyls (48) with mineral acids resulted in disproportionation to 1,2,3,4-tetrahydro-1,2,4,5-tetrazines (75) and l,6-dihydro-l,2,4,5-tetrazinium salts (76). Here one molecule of the verdazyl is reduced to (75) and the other is oxidized to (76). The mechanism of this reaction has been studied by Polumbrik and his group (72ZOR1925). Heating 3-phenyl-1,2-dihydro-1,2,4,5-tetrazine-6(5/f)-thione (77) in 2N hydrochloric acid led to the isolation of 3-phenyl-l,2,4-triazole-5-thione (78) (77KGS1564). 

Substituents present in the starting material affected product composition according to a series of perceptions extracted from the outcome of the reaction of selected 2-phenyl-l,2,3-triazole 1-oxides with AcCl as illustrated in Scheme 120 (1981JCS(P1)503,1997BSB717). The reasoning is based upon initial formation of an O-acetylated species shown in the left column, which then reacts with acetate ion in the product-determining step. The O-acylated species may react in a similar fashion with other nucleophiles like the chloride ion. 

In C5 unsubstituted 2-methyl or 2-phenyl-l,2,3-triazole 1-oxides the intermediates 400 and 403 react at C5. A methyl group at C4 does not significantly influence product composition. The chloro analogue 380 is formed in minor amounts and is easy to remove. The reaction gives access to substituted acetoxy-l,2,3-triazoles 405 and 406. 

Methylsulfonyl)-3-phenyl-3//-l,2,3-triazol[4,5-d]pyrimidine 176 was prepared by the reaction of 175 with sodium methyl sulfide, followed by oxidation with potassium permanganate in acetic acid. A nucleophilic substitution reaction on 176 with potassium cyanide gave 182, but the same reaction did not take place on 175. Treatment of 176 with sodium methoxide... 

The triazolo-fused 1,2,3,4-tetrazine 494 was obtained in good yield on oxidation of l-amino-5-phenyl-l,2,3-triazolo[4,5-d -, 2,3-triazole 493 with lead tetraacetate (Scheme 258) <1988CC1608>. Fused 1,2,3,4-tetrazines 496 were prepared via reaction of diazocyclopentadienes 495 with methyllithium, followed by a diazo transfer using tosyl azide, as shown in Scheme 259 <1994CB1479, CHEC-III(9.13.9.2.1)730>. 

Reaction with phenylhydrazine hydrochloride141 produces the isolable, ring-opened l-acyl-5-phenyl-diaminoguanidine hydrochloride (58), the free base of which is partly oxidized even by atmospheric oxygen to l-acyl-3-amino-5-phenylformazane. Cyclization of 58 with alkali produces arylhydrazino- or arylazo-1,2,4-triazoles (59) heating 58 in butanol produces 3,4-diamino-l,2,4-triazole (60). 

The most commonly employed diazenes, e.g., diethyl, bis(2,2,2-trichloroethyl), and di-/m-butyl diazenedicarboxylate, and 4-phenyl-3/7-1,2,4-triazole-3,5(4/7 )-dione, are commercially available. However, various new reagents or methods recently introduced for the preparation of specific diazenes from hydrazines can be successfully applied to other hydrazines. Especially important is the development of chemoselective methods for converting hydrazines to diazenes in the presence of unsaturated substrates, for example in intramolecular cycloaddition reactions (Section 7.2.10.3.10.2.), where either the (di)ene group and other functions present in the substrate are sensitive to the (oxidizing) reagent employed. 

On the other hand, the diazetidines 5 and 7 only are produced by the reaction of indene with phthalazine-l,4-dione (4)4 and 4-phenyl-3//-l,2,4-triazole-3,5(4//)-dione (6)1. The adduct 7 was successively converted to fra .v-(l,2-dihydro-3-hydroxy-2-indenyl)triazolidinone by acidic hydrolysis T Furthermore, the diazctine was prepared by a sequence involving hydrolysis of the triazolidine ring with concomitant decarboxylation, and oxidation of the intermediate diaze-tidine5. 

Alkenyl- and alkynyl-triazoles have received little attention. By analogy with the behaviour of other azoles they are expected to polymerize but to be less reactive in addition reactions than alkenes or alkynes. Although the most promising polymers derived from triazoles are obtained by different methods (see Section 4.12.5.2.3), some information is available on potentially polymerizable vinyltriazole (63MI4120i). The styryltriazole (134) could be oxidized to 3-methyl-l-phenyl-l,2,4-triazole, i.e. without affecting either the triazole or iV-phenyl ring, but hydroxylation of the alkene chain failed (s4JCS4256). 

Dickinson and Jacobsen [74AC298 75JCS(P1)975] prepared 1,2,4-triazolo[4,3-6]1.2,4,5-tetrazine 520 by reacting 6-phenyl-3-hydrazino-1,2,4,5-tetrazine (519) with carbon disulfide or by reacting 4-amino-5-hydrazino-l,2,4-triazol-3-thione (522) with benzaldehyde in alkaline medium. The reaction involved the air oxidation of tetrahydrotriazolo-... 

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