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1.2.4- Triazoline-3,5-diones, decomposition

The coupling reaction is very fast because unstable cyclopentadienols resulting from the decomposition of ferrocenium cations can be trapped, in good yields (80%), by triazoline diones [73]. The cycloadduct is obtained with totally regio and stereo selectivities (Scheme 51). [Pg.357]

Substituted l,2,4-triazoline-3,5-diones are excellent dienophiles which react rapidly at room temperature with oxepins, but particularly with the arene oxide valence tautomer. A similar [4+2] cycloaddition reaction between the episulfide tautomer of thiepin (44) and 4-phenyl-l,2,4-triazoline-3,5-dione has been reported (74AG(E)736>. Benzene episulfide (the valence tautomer of thiepin 44) was generated in situ by thermal decomposition of the diepisulfide (151) at 20 °C and trapped as a cycloadduct at the same temperature (equation 34). A 1,3-dipolar cycloaddition reaction between thiepin (152) and diazomethane has been reported (56CB2608). Two possible cycloadduct products are shown since the final structure has not been unequivocally established (equation 35). [Pg.577]

Photolysis and thermolysis of 4-aryl-l,2,4-triazoline-3,5-diones (70, R = aryl) have been studied by Wamhoff and Wald (77CB1699). Photolysis produces the same products as were found in FVP. The thermal conversion of 70, R = Ph, into the corresponding s-triazolo[l,2-a]-s-triazole derivative, which takes place below the decomposition temperature of the educt, is assumed to proceed via a radical chain reaction (Scheme 8). [Pg.400]

Where the carbon-carbon double bond is a part of an aromatic system, in general, cyclopropanation of diazoketones results in the formation of unstable cyclopropane adducts. For example, Saba140 has shown that in the intramolecular cyclopropanation of diazoketone 57 the norcaradiene ketone 58 can be detected by low-temperature NMR and can be trapped in a Diels Alder reaction with 4-phenyl-l,2,4-triazoline-3,5-dione (equation 69). In addition, Wenkert and Liu have isolated the stable norcaradiene 60 from the rhodium catalysed decomposition of diazoketone 59 (equation 70)105. Cyclopropyl ketones derived from intramolecular cyclopropanation of hetereoaromatic diazoketones are also known and two representative examples are shown in equations 71 and 72106. Rhodium(II) compounds are the most suitable catalysts for the cyclopropanation of aromatic diazoketones. [Pg.675]

In general, reaction of (110) with a wide variety of dienes was quite satisfactory (67JOC330). Only the most unreactive dienes such as hexachl-orocyclopentadiene and hexachlorobutadiene failed to react under the conditions employed. The chief limitation of this dienophile is that the mixture cannot be heated to force reaction without the decomposition of (110). Another important observation was the strong, almost complete preference for undergoing the Diels-Alder-type addition even when other reactions are possible. This may be attributed to the two favorable factors of cis configuration and electron deficiency that are exhibited by 4-phenyl-1,2,4-triazoline-3,5-dione. [Pg.203]


See other pages where 1.2.4- Triazoline-3,5-diones, decomposition is mentioned: [Pg.154]    [Pg.57]    [Pg.563]    [Pg.92]    [Pg.563]    [Pg.225]    [Pg.74]   
See also in sourсe #XX -- [ Pg.72 , Pg.399 ]




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1.2.4- Triazoline-3,5-dione

1.2.4- Triazoline-3,5-diones

Triazoline

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