Methyl triazolinedione

Simple 2/7-chromenes produce [2+2] cycloaddition products upon reaction with triazolinediones such as phenyl-triazolinedione (PTAD) and methyl triazolinedione (MTAD) (Equation 11) <1995T13277>. 

Density functional theory has been used to investigate the Diels-Alder reactions of triazolinedione with s-cis- and. y-fran -butadiene. " Combined quantum mechanics-molecular mechanics calculations have been used to investigate the asymmetric Diels-Alder reaction of cyclopentadiene with the complex dienophiles AICI3-methyl acrylate and methoxyaluminium dichloride-acrolein.Equilibrium constants have been determined for the molecular complexes formed from 1-alkyl-1-(2-naphthyl)ethenes and 1-vinylnaphthalene with TCNE in C1(CH2)2C1 at 27.1 °C ... 

Within the framework of reactions of various propellane substrates with very reactive dienophiles, N-methyl- and iV-phenyl-triazolinediones, l,6-methano[10]annulene itself and many bridge- and ring-substituted derivatives were subjected to such Diels-Alder reactions. All of the products are (more complex) [4.4.1]propellane derivatives. In general it is clear that the rates of reaction are very much slower than those of various tetraenic. 

That this difference in (4+2)-cycloaddition behavior most likely has steric origins—the methyl groups in 150 or the derived monoadduct preventing an ortho -addition of two equivalents of the dienophile—is supported by the observation that permethyl[6]radialene 95 is inert even towards the extremely reactive dienophile 4-phenyl-1,2,4-triazolinedione. ... 

P(0)(0Me)2] gives the pyrans 65a-b and the diazepines 67a-b. Diazepines 67a-b are formed by spontaneous isomerization of the intermediate 2-(diazomethyl)-2//-pyrans 66a-b (87JOC3851). In contrast, the analogous reactions of 4-methyl-2,6-diphenylpyrylium tetrafluoroborate 63b with 64a-b give only 68a-b. The allylpalladium chloride-catalyzed decomposition of 65a-b and 68a-b in benzene solution gives 92-98% of oxepines 69a-b,d. Oxepines 69a-b,d react with triazolinedione 55 to form the Diels-Alder adducts 70a-b,d (83-89%), which are derived from the valence tautomeric benzene oxides. The corresponding reaction of 69c with 55 under otherwise identical conditions proceeds differently in that an isomer with structure 70 c (66%) is formed along with 70c (23%). 

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