Dimethyl-s-tetrazine

By combining the two-step excitation TG technique with the population grating (Section II.C), the rates and the quantum yield of reactions from higher excited states were determined for dimethyl-s-tetrazine [35] (Scheme 10). 

Figure 15 Rotational tunnelling relaxation rate as a function of temperature in a log-log representation. Fitted curves are based on Raman-type relaxation processes. Note that the tunnelling relaxation in the deuterated rotor is faster by two orders of magnitude. The sample is dimethyl-s-tetrazine in n-octane.

The generation and trapping of 5,6-bis(trimethylsilyl)benzo[c]furan 126 was reported by Wong utilizing Warrener s s-tetrazine methodology. The trapping of the silylated isobenzofuran with A-phenylmaleimide is illustrated below. A number of other dienophiles such as dimethyl acetylenedicarboxylate, benzoquinone, naphthoquinone and anthra-l,4-quinone have also been used <00TL5957>. 

Dimethyl 1,2,4,5-tetrazlne-3,6-dicarboxylate s-Tetrazine-3,6-dicarboxylic acid, dimethyl ester (8) 1,2,4,5-Tetrazine-3,6-dicarboxylic acid, dimethyl ester (9) (2166-14-5)... 

C2 9H3 5CIN2O3, 4-(p-Chlorophenyl)-4-hydroxy-N,N-dimethyl-a,a-diphen-ylpiperidine-1-butyramide hydrate, 43B, 315 C3 0H3 2Ni,, 1,2,4,5-Tetrabenzylhexahydro-s-tetrazine, 44B, 223 C3 0H3 5CIN2O2, 4-(p-Chlorophenyl)-4-hydroxy-N,N,7-trimethyl-a,a-di-phenyl-1-piperidinebutyramide, 43B, 315 C30H35F2N3O, 4-(4,4-Bis(p-fluorophenyl)butyl)-1-piperazineacetyl-2 ,6 -xylidide, 43B, 316... 

In sharp contrast to the uncomplexed l//-azepine, which yields a C4 — C5 adduct, the tricarbonyliron complex of ethyl 1 W-azepine-l-carboxylate with dimethyl l,2,4,5-tetrazine-3,6-dicar-boxylate furnishes the C2 —C3 adduct 4 in excellent yield.273 Likewise, cycloaddition with 2,3,4,5-tetrachlorothiophene 1,1-dioxide yields adduct S.131... 

Preparation and Diels-Alder Reaction of a Reactive, Electron-Deficient Heterocyclic Azadiene Dimethyl 1,2,4,5-Tetrazine-3,S-Dicarboxylate. 1,2-Diazine and Pyrrole Introduction. 

With azines the situation is varied. In the radical cations of pyridine and diazines the semi-occupied orbital is largely confined to the nn orbital(s) (see Scheme 2, structure 2), while the radical cation is of the n type with monoazanaphthalenes, -phenanthrenes and -anthracenes. The situation might change with substitution. As an example, alkylpyridine radical cations are of the n type, like the parent compound, whereas for the 2,5-dimethyl, 2-chloro, and 2-bromo derivatives the structure is of the n type [13]. Likewise, with benzo[c]cinnoline the parent compound and its alkyl derivatives give an n radical cation, but with some dimethoxy derivatives a n structure is found [14] and a switch from n to 7t structure occurs also in passing from 1,2,4,5-tetrazine to its 3,6-diamino derivatives [15]. 

Dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate (3) affords the following products when reacted with nucleophiles water affords the hydrazide 4, ammonia and dimethylamine the amidrazone 5, methylamine the 1,2,4-triazine 6 and methanol (X = O) or methanethiol (X = S) the dihy-dropyrazoles 7.288... 

Figure 7 Rate constants (10 Aj 1 mol s , 20°C, acetonitrile) for the reaction of l-iV,iV-dimethyl-aminopropyne with heteroaryl 3,6-disubstituted 1,2,4,5-tetrazines.

Dale L. Boger, James S. Panek, and Mona Patel 79 PREPARATION AND DIELS-ALDER REACTION OF A REACTIVE, ELECTRON-DEFICIENT HETEROCYCLIC AZADIENE DIMETHYL 1,2,4,5-TETRAZINE-3,6-DICARBOX-YLATE. 1,2-DIAZINE AND PYRROLE INTRODUCTION... 

After Huisgen s explanatory review, there was still silence on this reaction in the scientific community for some years until it was realized by Carboni and Lindsey (1962) that substituted 1,2,4,5-tetrazines are very reactive towards simple alkenes. Sauer et al. (1965), working in the same department as Huisgen at the University of Munich, evaluated such reactions in more detail, including alkynes in addition to alkenes. In the 1970 s, dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate (9.38) became much in demand as a synthon. It is obtained easily by esterification of 9.36, followed by treatment with nitrous gases (9-22 Organic Syntheses, Boger et al., 1992). 

The preparation of thioacethydrazide, MeCSNHNHj, has now been accomplished, both from the known nickel complex and from carboxymethyl dithio-acetate [MeC(=S)SCH2C02Hl and hydrazine. It is stable at —30 °C, but at room temperature it changes into l,4-dihydro-3,6-dimethyl-l,2,4,5-tetrazine and at its melting point (95—96 °C) into 4-amino-3,5-dimethyl-1,2,4-triazole. 

A review containing 123 references on recent mechanistic and theoretical studies of hetero-Diels-Alder reactions has been presented. The hetero-Diels-Alder reactions of homochiral 1,2-diazabuta-1,3-dienes with diethyl azodicarboxylate are accelerated by microwave irradiation to produce the corresponding functionalized 1,2,3,6-tetrahydro-l,2,3,4-tetrazines. " The transition structures for hetero-Diels-Alder reactions involving the heteroatoms O, S, and N in dienes and also in dienophiles were determined at the MP2 and the hybrid DPT levels of theory. The activation volume of the Diels-Alder reaction between dimethyl l,2,4,5-tetrazine-3,6-dicarboxylate and hex-l-ene indicates the conservation of all four nitrogen atoms in the transition state. " 4-n-Propyl-l,2,4-triazoline-3,5-dione reacts with cyclopentadienes, cyclohexadienes, and cycloheptadienes to yield 4 + 2-cycloadducts. ... 

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