syntheses of 3-aroylflavones have been established. In the first synthesis the use of microwave irradiation led to an improvement in the yields of both the Knoevenagel condensation of β-diketones with aldehydes to afford 3-aroylflavanones and of their oxidation to 3-aroylflavones. In the second and more general synthesis, a novel and efficient procedure for 3-aroylflavones involves a one-pot reaction between
Baker-Venkataraman Rearrangement Under Microwave Irradiation: A New Strategy for the Synthesis of 3-Aroyl-5-hydroxyflavones
作者:Artur Silva、Diana Pinto、José Cavaleiro
DOI:10.1055/s-2007-984525
日期:2007.7
Microwave irradiation selectively induces the Baker-Venkataraman rearrangement of 2′,6′-diaroyloxyacetophenones to give 3-aroyl-5-hydroxyflavones, in a very short reaction time. Under classical heating conditions these reactions afforded 5-hydroxyflavones as byproducts.
Flavones were prepared using a one-pot procedure starting from the corresponding 2'-hydroxyacetophenones. The latter were treated with 3 equiv of aroyl chloride in wet K2CO3/acetone (1% w/w water) to afford a good yield of flavone and a smaller amount of 3-aroylflavone. Evidence was obtained that the reaction proceeds via a triketone intermediate. When the reactants were heated in 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and pyridine, the 3-aroylflavone was obtained exclusively. Use of a stoichiometric amount of aroyl chloride afforded only the corresponding flavone. (C) 2011 Elsevier Ltd. All rights reserved.
Rao et al., Proceedings - Indian Academy of Sciences, Section A, 1947, vol. 25, p. 427,429