Synthesis of (E)-2-(4-Arylbut-1-en-3-ynyl)-4H-chromen-4-ones

Abstract

Chromones are a well-known class of naturally occurring oxygen-containing heterocyclic compounds; many of them playing important biological functions in nature.[IJ Although 2- methylchromones are one of the scarcest classes of natural chromones, their synthesis and reactivity is well studied. They can participate in several chemical transformations such as oxidation, thiation, hydrogenation, photolysis, cycloaddition and condensation reactions, being useful targets in the synthesis of novel heterocyclic compounds. [lJ The acidity of the 2-methyl group, due to the low electron density at C-2 caused by oxygen atom and the α, β-unsaturated ketone system, led us to explore the condensation of 2-methylchromone 2 with propargyl aldehydes 3 in order to obtain new (£)-2-( 4-arylbut-1-en-3-ynyl)-4Hchromen- 4-ones 4 (Scheme 1). The starting material, 2-methyl-chromone 2 was prepared in a three step sequence starting from 2 '-hydroxyacetophenone 1 while the propargyl aldehydes 3were obtained from the reaction of the appropriate iodobenzene with propargyl alcohol and subsequent oxidation. In this communication we will present the synthetic details of all described transformations as well as the structural characterization (by 1 D and 2D NMR studies) of the new synthesized compounds. ; University of Aveiro, Fundat;iio para a Ciencia e Tecnologia (FCT, Portugal), European Union, QREN, FEDER and COMPETE for funding the QOPNA Research Unit (project PEst-CIQUJ/UJ0062/2011) and the Portuguese National NMR Network. Helio Albuquerquealso thanks FCT for his fel/owship(SFRH/BI/51556/20 11).