(E)‐2‐(4‐Arylbut‐1‐en‐3‐yn‐1‐yl)chromones as Synthons for the Synthesis of Xanthone‐1,2,3‐triazole Dyads

Abstract

Xanthone-1,2,3-triazole dyads have been synthesized by two different approaches, both starting from novel (E)-2-(4-arylbut-1-en-3-yn-1-yl)chromones, prepared through a base-catalyzed aldol reaction of 2-methylchromone and arylpropargyl aldehydes. In the first method, the xanthone moiety is built by Diels-Alder reaction of the referred unsaturated chromones with N-methylmaleimide under microwave irradiation, followed by oxidation of the obtained adducts with

Microwave Irradiation: Alternative Heating Process for the Synthesis of Biologically Applicable Chromones, Quinolones, and Their Precursors

“…Following these earlier studies in DA reactions with ( E )- and ( Z )-3-styryl-4 H -chromen-4-ones as dienes, years later, we also explored the reactivity of particular chromone derivatives 23 and 25 to develop a method for the synthesis of 9 H -xanthen-9-one-1,2,3-triazole hybrids 27 ( Scheme 8 ) [ 48 ]. The diene of chromones 23 showed very low reactivity in classical heating conditions using maleimides as dienophiles.…”

Recent advances in the synthesis of xanthones and azaxanthones

“…Xanthone-1,2,3-triazole dyads were obtained by two different approaches, both starting from (E)-2-(4-arylbut-1-en-3-yn-1-yl) chromones, previously obtained by a base-catalysed aldol reaction of 2-methylchromone and arylpropargyl aldehydes. 173 While the first approach adopted a methodology in which the xanthone core is primarily constructed using chromones as dienes in the Diels-Alder reaction, followed by the construction of the triazole ring, in the second strategy the process was inverted, staring with the triazole ring followed by the construction of the xanthone core (Scheme 17A). Thus, in the first methodology, a Diels-Alder reaction of the chromone derivatives 108 with N-methylmaleimide under microwave irradiation gave Diels-Alder adducts 109.…”

“…The second approach consisted of a 1,3-cycloaddition reaction of chromones 108 with sodium azide to form the triazole derivatives ( 112) followed by methylation of the triazole NH group prior to the Diels-Alder reaction with N-methylmaleimide and oxidation with DDQ to provide the xanthone-1,2,3-triazole dyads (111) in moderate to good yields (57-80%). 173 (E)-2′-Propargyloxy-2-styrylchromones (115) were used as substrates in a microwave-assisted intramolecular Diels-Alder reaction, affording chromeno [3,4-b]-xanthones 116 (Scheme 17B). 174 During optimization processes, besides the variation of solvent, Lewis acid, temperature, and reaction time, different oxidizing agents were also tested in order to push the reaction towards the oxidized product 116, without the formation of secondary products that are not fully oxidized.…”

“…A myriad of examples have been described in the literature, including the reaction with alkyl halides for the transformation into alkoxy, 43,59,69,[219][220][221][222][223] haloalkoxy, 18,51,69,99,224 methyl alkyl-or aryl-piperazine moieties, 225 epoxypropanoxy 65,103,[220][221][222] oxirane 221 , oxypropanolamines, 103 benzenesulfonamides, 226 and propargyloxy. 45,52,54,63,106,118,173,227,228 When reacted with other compounds that are not alkyl halides, several other functional-Scheme 25 Other methodologies for the synthesis of xanthones.…”

Rapid assembly of the procyanidin A skeleton

“…10 Our strategy involved the addition of two molecules of phloroglucinol to acetylenic aldehyde 4, in Scheme 1. 11 The aldehyde 4 is readily available via a Sonogashira reaction of an aryl halide with propargyl alcohol followed by oxidation with MnO2, Scheme 1. We studied 5, the product from the reaction of 4 (R = OMe) with phloroglucinol and p-toluenesulfonic acid (PTSA), using 1 H NMR, 13 C NMR, and 2D NOESY NMR.…”