- Catalysis and regioselectivity in the Michael addition of azoles. Kinetic vs. thermodynamic control
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Bicyclic guanidine bases, TBD and MTBD were found to be high]y efficient catalysts in the Michael addition of azoles with α,β-unsaturated nitriles and esters. The factors influencing regioselectivity have been elucidated, and some new azole-Michael adduct
- Horvath, Andras
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p. 4423 - 4426
(2007/10/03)
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- Michael adducts in regioselective synthesis of N-substituted azoles
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Michael adducts of azoles (4-phenyl-, 4-methyl- and 4-nitroimidazole, 4-methylbenzimidazole, 1,2,4-triazole and theophylline) are shown to be valuable substrates for obtaining the N-substituted derivatives of the parent heterocycles by a quaternization-Hofmann elimination sequence. The effectiveness of the procedure is dependent on the regiochemical outcome of the first, N-protective step, i.e. the Michael addition. By choosing the appropriate Michael acceptor, alkylating agent and deprotection conditions, the thermodynamically less stable regioisomers of N-substituted azoles have been obtained in high yields.
- Horvath
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p. 1183 - 1189
(2007/10/02)
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