1,2,4,5-Tetrazine-3,6-dicarboxylic acid, 1,2-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)... 

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

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. . 

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-... 

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. 

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) ... 

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