Dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate

Tautomerism of tetrazines was investigated by ID 15N INADEQUATE.85 Dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate can exist either in 1,2- (8) or... 

S. Dihydro-1,2,4,5-tetrazine-3,6-dicarboxylic acid. A 2-L, three-necked, round-bottomed flask is equipped with an overhead stirrer and a 100-mL addition funnei. Disodium dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate (90.37 g 0.42 mol) in 100 mL of water and 100 g of crushed ice are added. The resulting slurry is cooled with an ice/sodium chloride bath and a solution of concentrated hydrochloric acid (84 mL of 36-38%) is added dropwise with stirring over 45 min. The reaction mixture is washed five times with 200 mL of dry ether and the ether layer is decanted. The product is immediately collected by filtration using a BOchner funnel. Drying the collected solid at room temperature under reduced pressure affords 51.6-53.06 g (72-74%) of dihydro-... 

Disodium dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate 1,2,4,5-Tetrazine-3,6-dicarboxylic acid, 1.2-dihydro-, disodium salt (11) (96898-32-7)... 

DIHYDROPYRIDINE EQUIVALENT, 70, 54 Dihydroquinidine, benzoate ester, 70, 49 DIhydroquinIdIne 4-chlorobenzoate, 70, 47 Dihydroquinidine, 2-naphthoate ester, 70, 49 Dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate, 70, 80 Dilsobutylaluminum hydride, 70, 20... 

The submitters employed, without purification, thionyl chloride obtained from Fisher Scientific Company. The procedure should be performed in a well-ventilated hood since thionyl chloride Is a lachrymator. The yield of dimethyl ester was found to be lower in instances when the thienyl chloride-methanol solution was not allowed to stir (30 min, -30°C) prior to the addition of dihydro-1,2,4,5-tetrazine-3,6-dicarboxylic acid. 

A Disodium dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate. A 2-L, three-necked, round-bottomed flask is equipped with an overhead stirrer, thermometer, and a 500-mL addition funnel. Sodium hydroxide (320 g, 8 mol) and 500 mL of water are added. Ethyl diazoacetate (200 g, 1.75 mol, Note 1) is placed in the addition funnel and added dropwise to the stirred sodium hydroxide solution so as to maintain the temperature of the reaction mixture between 60°C and 80°C (approximately 1.5 hr, Note 2). After the reaction slurry is cooled to room temperature, it is poured into 2 L of 95% ethanol, mixed well, and the liquid is decanted. This washing procedure is repeated five times using 1.5 L of 95% ethanol each time. The precipitate is collected by filtration using a Buchner funnel, the collected solid is washed with 1 L of absolute ethanol and 1 L of ether, and dried (12 hr) in the air to afford 160-184 g (85-97%) of disodium dihydro-... 

Tetrazine-3,6-dicarboxylic acid, 1,6-dihydro-diethyl ester... 

The isomeric pyridazino[4,5-6]azepine 19 is obtained directly during the decomplexation of the [4 + 2] adduct 17 formed from tricarbonyl(ethyl +17/-azepine-l-carboxylate)iron and 1,2,4,5-tetrazine-3,6-dicarboxylate, with trimethylamine A-oxide.113 Surprisingly, decomplexation of adduct 17 with tetrachloro-l,2-benzoquinone yields only the dihydro derivative 18 (71 %), aromatization of which is achieved in high yield with trimethylamine A-oxide in refluxing benzene. 

Cycloaddition of dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate with EWG-substituted primary ketene N,0-acetals provides a tetrasubstituted pyridazine, methyl 4-amino-5,7-dioxo-6,7-dihydro-5/7-pyrrolo[3,4-4pyridazine-3-carboxylate <200681513>. 

Dihydro-sym-tetrazine-3,6-dicarboxylic Acid [called 1.2-Dihydro-1.2.4.5-tetrazindicarbon saure (3.6) BisdiazoessigsSure or "Triazoessigsaure in Ger],... 

Decarboxylation of l,2,4,5-tetrazine-3,6-dicarboxylic acid (221) and the dihydrodicar-boxylic acid (222) was used to prepare the parent 1,2,4,5-tetrazine (38) and the dihydro-1, 2,4,5-tetrazine (223), respectively <78HC(33)1075, p. 1078, 1888JPR(38)531,00CB58). 

See in Vol 2, B143-L under 3,6-Bis (fluorenyli-denhydro)-sym-tetrazine. . 1,2-Dihydro-Sym-Tetrazine-3,6-Dicarboxylic Acid. See in Vol 5, D1267-L Di(Tetrazolyl-5) 3,6- Dihydro-Sym-Tetrazine. See in Vol 2, B157-R to B158-L, under 3,6-Bis (2H-tetrazolyl-5)-dihydro-l, 2,4,5-tetra-zine. . 

One of the oldest methods for the preparation of 1,2,4,5-tetrazines is the dimerization of diazo compounds by base. In 1900 Hantzsch and Lehmann170 isolated a new compound when they treated ethyl diazoacetate with sodium hydroxide this compound was later shown to be disodium 1,4-dihydro-1,2,4,5-tetrazine-3,5-dicarboxylate.171 Esterification of the free acid and... 

Liberating the acid from the disodium salt with H2S04 decreases the yield of this step considerably. Dimethyl t,4-Dihydro-i,2,4J-tetrazine-3,6-dicarboxylate (2b) ... 

---