- Dipolar Cycloaddition Reactions of Diazoazoles with Electron-Rich and with Strained Unsaturated Compounds
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Regiospecific net 1,7-cycloaddition reactions of electron-rich or strained olefins and electron-donor acetylenes occur readily (-70 to -10 degC) with diazoazoles having nitrogen in the 2-positions of their azole rings.Diazoazoles such as 5-tert-butyl-3-diazo-3H-pyrazole (20), 3-diazo-5-phenyl-3H-pyrazole (24), 2-diazo-2H-imidazole (28), 4,5-dicyano-2-diazo-2H-imidazole (12), 4-diazo-4H-imidazole (63), 4-diazo-5-phenyl-4H-1,2,3-triazole (70), 5-cyano-4-diazo-4H-1,2,3-triazole (74), 3-diazo-3H-1,2,4-triazole (76), and 3-diazo-5-phenyl-3H-1,2,4-triazole (79) thus usually add effectively to unsaturated reactans such as enamines, 1-alkoxyalkenes, ketene acetals, aryl isocyanates, norbornene, and norbornadiene to give new 1,7-cycloadducts.These cyclization reactions may be followed by tautomerization processes leading to new stabilized fused heterocycles or by elimination to novel highly delocalized heteroaromatic derivatives. 4,5-Dicyano-2-diazo-2H-imidazole (12) undergoes various accelerated cycloadditions to unsaturates and adds to norbornene and norbornadiene by exclusive exo dipolar processes.Addition of activated acetylenes to representative α-diazoazoles also results in regiospecific 1,7-cyclization to give stabilized fused azolo heterocycles.
- Magee, W. L.,Rao, C. B.,Glinka, J.,Hui, H.,Amick, T. J.,et al.
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p. 5538 - 5548
(2007/10/02)
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- SUBSTITUENT AND COORDINATION EFFECTS IN SINGLET REACTIONS OF 3-DIAZO-3H-1,2,4-TRIAZOLES WITH SUBSTITUTED BENZENES AND NITRO COMPOUNDS
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3-Diazo-3H-1,2,4-triazoles convert to singlet 3H-1,2,4-triazol-3-ylidenes which (1) effect directed electrophilic substitutions of benzenes and (2) coordinate with benzenoid substituents and nitro compounds to give decomposition or rearrangement products.
- Glinka, J.,Fiscus, D.,Rao, C. B.,Shechter, H.
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p. 3221 - 3224
(2007/10/02)
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- KINETICS OF REACTIONS OF 1,2,4-TRIAZOLES-3-DIAZONIUM IONS WITH PHENOL AND WITH HYDROXYL ION
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5-Methyl and 5-phenyl-1,2,4-triazole-3-diazonium ions (IIIa, IIIb) react with undissociated phenol in diluted hydrochloric acid.At pH>1 the reactions with phenolate ions become kinetically significant, their bimolecular rate constants approaching those of
- Machacek, Vladimir,Korinek, Josef,Kreuzigova, Daniela,Sterba, Vojeslav
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p. 658 - 674
(2007/10/02)
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- Reactions with Diazoazoles. Part VI. Unequivocal Synthesis of 3-Methyl-3H-azolotetrazoles. Correction of the Formerly Described 3-Methylazolotetrazoles in Favour of Mesoionic 2-Methylazotetrazoles
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3-Methyl-3H-pyrazolotetrazoles 2 and 3-methyl-6-phenyl-3H-1,2,4-triazolotetrazole (4) have been unequivocally synthesized by annelation of the tetrazole moiety to the pyrazole resp. 1,2,4-triazole system.The constitution of some N-methyl substituted azolotetrazoles, formerly described as 3-methyl-3H-pyrazolotetrazoles 2, 3-methyl-6-phenyl-3H-1,2,4-triazolotetrazole (4) and 1-methyl-6-phenyl-1H-1,2,4-triazolotetrazole (5), has to be revised in favour of the corresponding mesoionic 2-methyl derivatives 2', 4', 5'.The structures of 3-methyl-3H- as well as of 2-methyl-2H-pyrazolotetrazole derivatives 2a, 2c, 2'a have been determined by X-ray analyses.The azapentalenic system is aromatic in all three measured compounds and mesoionic in the case of the 2-methyl-2H-substitution pattern.The phenyl and ester substituents are coplanar with the azapentalene system. 3-, 2-, and 1-Methylpyrazolotetrazoles exhibit different behaviour when allowed to react wit stannous chloride or sodium ethoxide.Azolotetrazoles with a methyl substituent at N-1, N-2 or N-3 of the tetrazole moiety can be distinguished by a combination of 1H and 13C nmr with respect to the chemical shifts of the N-methyl group and the bridgehead carbon.Results of semiempirical calculations of the pyrazolotetrazole anion and of its N-methyl derivatives are discussed.
- Ege, Guenter,Heck, Reinhard,Gilbert, Karlheinz,Irngartinger, Hermann,Huber-Patz, Ursula,Rodewald, Hans
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p. 1629 - 1639
(2007/10/02)
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- Higher Order Dipolar Cycloaddition Reactions of Diazoazoles with Electron-Rich Dipolarophiles
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A study of the cycloaddition behavior of a series of diazoazoles with electron-rich dipolarophiles has been carried out. 3-Diazo-4-methyl-5-phenylpyrazole readily reacts with ynamines, enamines, and vinyl ethers to give 1,7-cycloadducts.The trisubstituted
- Padwa, Albert,Kumagai, Tsutomu,Woolhouse, Anthony D.
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p. 2330 - 2336
(2007/10/02)
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