DBU-catalyzed one-pot cascade reaction of propargylamines and water for the synthesis of flavanones has been developed. This process proceeds via a sequence of 1,4-conjugate addition of water to alkynyl o-quinone methide (o-AQM), followed by the alkyne–allene isomerization and subsequent intramolecular oxa-Michael addition. This strategy provides a convenient method for accessing a broad range of flavanones
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.