Asymmetric synthesis of 3-benzofuranones through 5-exo-trig cyclization of 4-nitroaryl olefins
作者:Nishant Verma、Sumit Kumar、Naseem Ahmed
DOI:10.1016/j.tetlet.2016.06.118
日期:2016.8
enantioselective cyclization via intramolecular 5-exo-trigonal cyclization to give 4-nitroaryl-3-benzofuranones. The product formation indicated that the proline bases (organocatalysts) suppressed the effect of carbonyl group by iminium ion formation and hence Michael addition is not possible. The conjugation effect moved toward 4-nitroaryl moiety suitable for 5-exo-trig cyclization (Baldwin’s rule)
Piperidine-mediated annulation of 2-acylphenols with 4-nitrobenzaldehyde to 3-benzofuranones
作者:Nishant Verma、Varun Kundi、Naseem Ahmed
DOI:10.1016/j.tetlet.2015.05.023
日期:2015.7
Piperidine mediated reactions of 2-acylphenols and 4-nitrobenzaldehydes afforded 3-benzofuranones in high yield (82-95%) at reflux temperature in ethanol. The electron density calculation of HOMO-LUMO energy in the chalcone intermediates by DFT showed the influence of the 4-nitro group and alkyl chain at C-2 position for the regioselective products. However, the reaction of 2- and 3-nitrobenzaldehydes with 2-acylphenols afforded flavones and flavanones, respectively, under the same reaction conditions. The substituent position effects were further studied in respect of 2-, 3- and 4-nitro substituted benzaldehydes and 2-acylphenols in the product formation. (C) 2015 Elsevier Ltd. All rights reserved.
The Alkyl Derivatives of Halogen Phenols and their Bactericidal Action. I. Chlorophenols
作者:Emil Klarmann、Vladimir A. Shternov、Louis W. Gates