4- Methyl-l,2,4-triazoline-3,5-dione

The reaction of 4-methyl-l,2,4-triazoline-3,5-dione 428 with tetracyclopropylethylene gives 5,5,6,6-tetracyclopropyl-3-methyl-5,6-dihydro-oxazolo[3,2-A][l,2,4]triazolium-2-olate 140 (unreported yield) (Equation 89) <2004JA700>. 

Coupling of excess (Z)-l,2-dichloroethene (217) with propargyl alcohol first led to the enyne 218, which, when subjected to a second Pd-catalyzed coupling step with trimethylsilylacetylene, provided the mixed diacetylene 219. With all carbon atoms assembled, the allene function was generated by first producing the (unprotected) hydrazine derivative 220, which on treatment with either diethyl azodicarboxylate (DEAD) or 4-methyl-l,2,4-triazoline-3,5-dione (MTAD) under anaerobic conditions at 0 °C yielded the hydrocarbon 27. According to mechanistic studies, the latter process leads first to a mixture of ( )- and (Z)-diazenes. Sigmatropic elimination of... 

The structure of 91, a new bisaikylidenesilirane (sila[3]radialene) system, was confirmed by X-ray structure analysis (Figure 3c). Because of the high kinetic stability of 91 due to steric protection, aldehydes such as benzaldehyde as well as ketones did not react. However, [2 + 4] cycloaddition chemistry of 91 with 4-methyl-l,2,4-triazoline-3,5-dione resulted in the formation of a new ring-fused silirene (97) (equation 26). 

A 1,4-dipolar cycloaddition between tetrahydropyrido[l,2-a]pyrimidi-none 114 (R = Me) and 4-methyl-l, 2,4-triazoline-3,5-dione 666gave stable adduct 667 in acetonitrile or in acetic acid at room temperature for 1 hour (Scheme 44) (85CB4567). When ethyl cyanoformate was used as dienophile in boiling toluene for 20 hours, ethyl 3-methyl-4-oxo-6,7,8,9-tetrahydro-4//-pyrido[ 1,2-a]pyrimidine-2-carboxylate 669 was obtained (86CB1445). Pyrido[l,2-a]pyrimidine-2-carboxylate 669 was formed from the initial adduct 668 by elimination of phenyl isocyanate. Reaction of tetrahydropyr-ido[l,2-a]pyrimidinone 114 (R = Me) with l-(diethylamino)-l-propyne in... 

The aziridinofullerenes and azafulleroids obtained by Mattay et al. were subjected to further reactions to yield fullerene adducts of the second generation. As a model compound 4-methyl-l,2,4-triazoline-3,5-dione (NMTAD) 187, which is one of the most reactive dienophiles for Diels-Alder reactions, was selected. Sheridan et al. studied the photoinduced [4 + 2] cycloadditions of NMTAD to arenes [295], With alkenes, however, NMTAD reacts in photoinduced cycloadditions in a [2 + 2] fashion under formation of diazetidines [296], Both the sulfonyl-azafulleroids (185) and aziridinofullerene (186) were irradiated at 420 nm to give both the same [2 + 2] cycloadduct 186 (Scheme 71) [291], This indicates that at a certain stage rearrangements must be involved. 

Oxidation of hydrazines to diazines. Propargylic hydrazines are oxidized rapidly and efficiently in CH3OH at 0° by 4-methyl-l,2,4-triazoline-3,5-dione (MTAD) or diethyl azodicarboxylate (DEAD) with evolution of nitrogen to provide the corresponding allenes in 50-70% yield. The reaction occurs with high stereospecificity, and can be used to obtain optically active allenes (equation I).1... 

Products F and G were in turn substrates for subsequent pairing reactions to obtain multicyclic compounds J, N, K, O, and H. Finally, products B, J, and H, which all comprise a diene functionality could be further converted by a subsequent Diels-Alder (DA) reaction with 4-methyl-l,2,4-triazolin-3,5-dione to obtain the highly complex products I, M, and L. This example shows that by applying the build/couple/pair strategy a collection of 15 highly diverse (and complex) scaffolds can be obtained in only three to five steps. ... 

The photochemical cycloaddition of 4-methyl-l,2,4-triazoline-3,5-dione to the dibenzo-cyclooctatetraene 289 yields 3.5% of the cycloadduct 290, together with 36% of 291, the product of a di-jr-methane rearrangement (equation 153. Anthrasteroids 293 (R = H, Ac or COPh) are produced in an oxidative rearrangement when the phenyltriazoline-dione adduct of 292 is treated with boron trifluoride etherate. The 5,7-diene system of ergosteryl acetate 294 can be protected by cycloadduct formation, allowing selective hydrogenation of the 22,23-double bond " ... 

Diels-Alder dienophiles Dichlorovinylene carbonate. Dicyanoacetylene. Diethyl azodicar-boxylate. Dimethyl acetylenedicarboxylate. Ethylene, see 5,5-Dimethoxy-l,2,3,4-tetra-chlorocyclopentadiene. 4-Methyl-l,2,4-triazoline-3,5-dione. 4-Phenyl-l,2,4-triazoline-3,5-dione. 1,4-Phthalazinedione. 

When iVj-acyl-tryptophans are exposed to strong acid, the indolium cation is trapped by cyclisation involving the side-chain nitrogen. Comparable tricycles result from phenylselenylation of protected tryptophan or reaction with 4-methyl-l,2,4-triazoline-3,5-dione, ° or dimethyl(succinimido)sulfonium chloride (a CH2SMe group ends up at the indole C-3)." If M-bromosuccinimide is employed, the initially formed 3-bromo-tricycle loses hydrogen bromide to produce an aromatic indole. ... 

The most frequently used l,2,4-triazoline-3,5-diones include 4-methyl-l,2,4-triazoline-3,5-dione (MTAD) (2) and 4-phenyl-l,2,4-triazoline-3,5-dione (PTAD) (3), also called the Cookson reagent. Many other substituted derivatives of PTAD are also known but not widely used. A similar situation is found with some bifunctional compounds 4, where X can be aliphatic, aromatic, or a combination of aromatic and aliphatic parts [72M11 78CB3519 79MI1, 79MI2 85MI1 87JPS(A)2781],... 

Spectrometry of 4-Methyl-l,2,4-triazoline-3,5-dione Adducts, Oil Chem. Soc. 75 ... 

An outstanding example of a branching pathway exploited complementary cyclisation reactions to yield alternative molecular scaffolds (Scheme 1.5). A four-component Petasis condensation reaction was used to assemble flexible cyclisation precursors e.g. 14). Alternative cyclisation reactions were then used to yield products with distinct molecular scaffolds Pd-catalysed cyclisation (- 15a) enyne metathesis (- 15b) Ru-catalysed cycloheptatriene formation (- 15c) Au-catalysed cyclisation of the alcohol onto the alkyne (- 15d) base-induced cyclisation (- 15e) Pauson-Khand reaction 15f) and Miesenheimer [ 2,3]-sigmatropic rearrangement (not shown). Four of these cyclisation reactions could be used again to convert the enyne 15e into molecules with four further scaffolds (17a-d). In addition, Diels Alder reactions with 4-methyl-l,2,4-triazoline-3,5-dione converted the dienes 15b, 17a and 17d... 

Dobson, G. (1998) Identification of Conjugated Fatty Acids by Gas Chromatography-Mass Spectrometry of 4-Methyl-l,2,4-triazoline-3,5-dione Adducts, J. Am. Oil Chem. Soc. 75, 137-142. 

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