- Chemical reactivity of 3-hydrazino-5,6-diphenyl-1,2,4-triazine towards π-acceptors activated carbonitriles
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Behaviour of 3-hydrazino-5,6-diphenyl-1,2,4-triazine 1 as electron donor towards different electron acceptors activated carbonitriles has been investigated and a novel fused heterocyclic system and 2,3-disubstituted 1,2,4-triazines have been obtained. Compound 1 reacts with 1,2-dicyanobenzene as π-acceptor in DMF to form benzencarboximidamide 16, while reaction of 1 with a-bromomalononitrile 17 in boiling DMF affords compound 18. On the other hand, compound 1 reacts with tetracyanoethane 23 in DMF to yield compound 24. The route of reaction in DMF indicates that charge-transfer complexation is the key intermediate to obtain new heterocyclic systems. Structures of the products are established by MS, IR, UV-Vis, CHN and 1H NMR spectral data.
- Abdel-Rahman,Abdel-Monem
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p. 838 - 846
(2008/09/18)
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- !,3-Dipolar cycloaddition of α-phenyl-N-tert-butylnitrone (PBN) to dichloro- and dibromo-malononitrile, chlorotricyanomethane and tetracyanomethane. Structure of products and kinetics of their formation
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The kinetics of cycloaddition between α-phenyl-N-tert-butylnitrone (PBN, IUPAC name: N-benzylidene-tert-butylamine N-oxide) and six activated nitriles R-CN, viz. dibromo- and dichloro-malononitrile (1a and 1b), chlorotricyanomethane (1c), tetracyanomethane (1d), trichloroacetonitrile (1e) and carbamoylchlorodicyanomethane (5), to give 2-tert-butyl-3-phenyl-5-R-2,3-dihydro-1,2,4-oxadiazoles 2a-e have been determined, as well as the similar reaction between 4-NO2PBN and 1c.The second-order rate constants for reaction between PBN and 1 in acetonitrile fall (relative rate constant in parenthesis) in the order of 1d (5.4*103) > 1c (3.1*102) > 1b (8) > 5 (not given) > 1e (9*10-3).The rate constants are slightly larger in non-polar solvents.The rate constants of the PNB-1c and PNB-1d cycloadditions (0.15 and 2.6 dm3 mol-1 s-1, respectively) are of the same magnitude as those recently used to classify thioketones as 'superdipolarophiles'.X-Ray crystal structures are reported for 2-tert-butyl-3-phenyl-5-(dichlorocyanomethyl)-2,3-dihydro-1,2,4-oxadiazole (2b) and 2-tert-butyl-3-phenyl-5-(chlorodicyanomethyl)-2,3-dihydro-1,2,4-oxadiazole (2c).
- Eberson, Lennart,McCullough, John J.,Hartshorn, Chris, M.,hartshorn, Michael P.
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