1.2.4- Triazolines-3,5-diones

Preparation of cholesta-5,7-diene-ia,3/3-diol a solution of 500 mg of the 1,4-cyclized adduct of cholesta-5,7-dien-3/3-ol-ia,2a-epoxideand 4-phenyl-1,2,4-triazoline-3,5-dione in 40 ml of tetrahydrofuran is added dropwise under agitation to a solution of 600 mg of lithium aluminum hydride in 30 ml of THF. Then, the reaction mixture liquid Is gently refluxed and boiled for 1 hour and cooled, and a saturated aqueous solution of sodium sulfate is added to the reaction mixture to decompose excessive lithium aluminum hydride. The organic solvent layer is separated and dried, and the solvent Is distilled. The residue Is purified by chromatography using a column packed with silica gel. Fractions eluted with ether-hexane (7 3 v/v) are collected, and recrystallization from the methanol gives 400 mg of cholesta-5,7-diene-la, 3/3-diol. 

When the thiiranoradialene sulphoxide 568 was treated with an equimolar amount of 4-substituted 1,2,4-triazoline-3,5-diones 569, the adducts 570 were formed in quantitative yields671 (equation 363). 

An example of a /zctcro-Diels-Alder reaction in SC-CO2 is the cycloaddition of anthracene with 4-phenyl-1,2,4-triazoline-3,5-dione, carried out at 40 °C and at a pressures between 75 and 216 bar [86]. The rate constant increases with decreasing pressure and the highest reactivity was observed at the critical pressure. The value of the rate constant at the critical pressure was higher than that observed in liquid CHCI3 and MeCN at the same temperature. At higher pressures, the rate is slower than that in the polar solvents, which reflects the apolar nature of SC-CO2 as a solvent. 

Triazoline-3,5-diones, 4-substituted-ene reactions with polydienes, 220 properties of modified polymers, 220... 

In 1974, Vogel and his coworkers62) reported the first synthesis of the syn-benzene bisepisulfide 119 and its thermal behavior. The bisepisulfide 119 is thermola-bile and decomposes at 20 °C with a half-life of about 30 min to form benzene and sulfur as final products. When the reaction was carried out in the presence of 4-phenyl-1,2,4-triazoline-3,5-dione (PTD), 119 gave the product 120 which corres-... 

Fig.8A,B Derivatization of Type I pheromones A Z7-12 OAc with dimethyl disulfide (DMDS) and mass spectra of the DMDS adduct B E5,Z7-12 OAc with 4-methyl-1,2,4-triazoline-3,5-dione (MTAD) and mass spectra of the MTAD adduct...

Methyl-3-(tetramethylcyc opropylidene)propene (176), obtained by isomerization of allene 175 with potassium ferr-butoxide, added to 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD, 177) at room temperature to give the Diels-Alder adduct 178 in 46% yield (Scheme 26) [43]. 

Gycloaddition reactions of betaine 64 with electron-deficient dipolarophiles, such as the extremely reactive 4-phenyl-1,2,4-triazoline-3,5-dione, gave the corresponding cycloadduct 65 isolated in quantitative yield (Equation 8) <1995T6651>. 

The attack from the less-hindered side and in which how the products formed by exo or endo additions vary has attracted great attention and a very interesting case of the reaction between naphthalene derivatives and 4 phenyl-1, 2, 4 triazoline 3, 5 dione (d) acting as dienophile has been reported by B.M. Jacobson in 1973. 

A case of a thermally induced phase change involving ring inversion was recently described by Kaftory (31). He found that a crystal of the exo isomer of the adduct, 7a, of ll-cyano-l,6-methano[10]annulene with 4-methyl-1,2,4-triazoline-3,5-dione is transformed to the endo isomer 7b on heating to 175°C. The process involves nucleation and growth of the product phase, but maintains... 

The syntheses have been reported of la,3/3-dihydroxy-4,4-dimethylcholesta-5,7-diene (269) and its 3a-epimer, along with the ergostane analogues/ As reported in the preliminary account, 4,4-dimethylcholesta-5,7-dien-3-one underwent the ene reaction with 4-phenyl-1,2,4-triazoline-3,5-dione to give (270) rather than the normal Diels-Alder adduct.Treatment of (270) with acid gave the trienone (271). Treatment of cholecalciferyl tosylate with aq. KHCO3-... 

We were not able to obtain any cycloadduct from unactivated 2-azadienes 139 and esters of acetylenedicarboxylic acid. However, we found that 139 did cycloadd to typical electron-poor dienophiles such as esters of azodicarboxylic acid and tetracyanoethylene (Scheme 62). Thus, diethyl and diisopropyl azodicarboxylates underwent a concerted [4 + 2] cycloaddition with 139 to afford in a stereoselective manner triazines 278 in 85-90% yield (86CC1179). The minor reaction-rate variations observed with the solvent polarity excluded zwitterionic intermediates on the other hand, AS was calculated to be 48.1 cal K 1 mol-1 in CC14, a value which is in the range of a concerted [4 + 2] cycloaddition. Azadienes 139 again reacted at room temperature with the cyclic azo derivative 4-phenyl-1,2,4-triazoline-3,5-dione, leading stereoselectively to bicyclic derivatives 279... 

A solution of 3-methylbicyclo[l. 1.0]butane-l-carbonitrile (0.43 g, 4.55 mmol) and 1-phenyl-1,2,4-triazoline-3.5-dione (0.79 g, 4.55 mmol) in CH2C12 (25 mL) was irradiated for 5 h with a 275-W sunlamp. When the initial ruby red solution had faded to pale yellow, the solvent was removed under reduced pressure. A yellowish glassy solid was obtained and repeated recrystallizations (hot CC14) gave the product yield 0.58 g (40 %) mp 103-105 C. 

Substituted l,2,4-triazoline-3,5-diones are excellent dienophiles which react rapidly at room temperature with oxepins, but particularly with the arene oxide valence tautomer. A similar [4 + 2] cycloaddition reaction between the episulfide tautomer of thiepin (44) and 4-phenyl-1,2,4-triazoline-3,5-dione has been reported (74AG(E)736). Benzene episulfide (the valence tautomer of thiepin 44) was generated in situ by thermal decomposition of the diepisulfide (151) at 20 °C and trapped as a cycloadduct at the same temperature (equation 34). A 1,3-dipolar cycloaddition reaction between thiepin (152) and diazomethane has been reported (56CB2608). Two possible cycloadduct products are shown since the final structure has not been unequivocally established (equation 35). 

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