Efficient Syntheses of New Polyhydroxylated 2,3‐Diaryl‐9H‐xanthen‐9‐ones

Abstract

A large number of hydroxylated 2,3-diaryl-9H-xanthen-9-ones have been synthesised by two different approaches, starting either from 3-bromo-2-methyl-4H-chromen-4-one or from (E)-3-bromo-2-styryl-4H-chromen-4-ones. The former method involves Heck reactions between 3-bromo-2-methyl-4H-chromen-4-one and styrenes, leading to (E)-2-methyl-3-styryl-4H-chromen-4-ones; these condensed with benzaldehyde to give (E,E)-2,3-distyryl-4H-chromen-4-ones, which led to the desired 2,3-diaryl-9H-xanthen-9-ones under reflux in 1,2,4-trichlorobenzene. 3-Bromo-2-styryl-4H-chromen-4-ones were obtained either by aldol condensations between 3-bromo-2-methyl-4H-chromen-4-one and benzaldehydes, or through Baker-Venkataraman rearrangements of 2-acetylphenyl cinnamates, followed by one-pot bromination/ cyclisation with phenyltrimethylammonium tribromide. The 2,3-diaryl-9H-xanthene-9-ones were obtained in one-pot transformations involving Heck reactions between (E)-3-

An Overview of 2‐Styrylchromones: Natural Occurrence, Synthesis, Reactivity and Biological Properties

“…[31] Under the same reaction conditions, the condensation of 2-methyl-3-styrylchromones with parent benzaldehyde provided a few examples of 2,3-distyrylchromones 21. [32] Condensation between 2-methyl-3-nitrochromones and benzaldehydes in dry methanol at reflux together with a few drops of piperidine afforded the corresponding 3-nitro-2-styrylchromones 22 in 70-80 % yields. [33] A wide range of 2-SCs 23, unsubstituted at C-3, were obtained by condensation between substituted 2-methylchromones and appropriate benzaldehydes in alkaline medium with ethanol as solvent at room temperature, [25,[34][35][36] 55°C [37] or boiling temperature [38] or even in methanol at reflux [39,40] (Scheme 4).…”

“…The classical approach involves a three-step sequence: (i) condensation of appropriate 2′-hydroxyacetophenones with cinnamoyl chlorides, (ii) base-promoted Baker-Venkataraman rearrangement [62,63] of the formed esters 31 into the 5-aryl-3-hydroxy-1-(2-hydroxyaryl)penta-2,4-dien-1-ones 32 (in equilibrium with the corresponding diketone form), and (iii) cyclodehydration to afford the desired 2-SCs 33 (Scheme 8). The cinnamoyl chlorides used in the esterification step may be commercially available or can be prepared in situ by treatment of the corresponding cinnamic acids with phosphoryl chloride in dry pyridine at room temperature or 60-90°C [7,8,18,19,32,45,47,[64][65][66][67][68][69][70][71][72][73][74] or with N,N-dicyclohexylcarbodiimide (DCC) in the presence of a catalytic amount of 4-pyrrolidinepyridine (4-PPy) in dichloromethane at room temperature. [13,75] Transposition of the cinnamoyl group from the 2′-position to position 2 of the acetophenone occurs in the presence of potassium hydroxide with DMSO [13,18,19,7,8,32,[67][68][69]71,73] or pyridine [47,64,70,73,74] as solvent, of sodium hydride in THF at reflux [8,45,65] or under less conventional c...…”

“…Various 3-bromo-2-styrylchromones 34 were obtained when 5-aryl-3-hydroxy-1-(2-hydroxyaryl)penta-2,4-dien-1-ones 32 were treated with bromine in 1,4-dioxane [64] and with phenyltrimethylammonium tribromide (PTT) in THF at room temperature (Scheme 9). [32,69] Treatment of penta-2,4-dien-1-ones with Nbromosuccinimide (NBS) in CCl 4 in the presence of benzoyl peroxide produces inseparable mixtures of 2-bromopenta-4-en-1,3-diones 35 and 3-bromo-2-styrylchromones 34 (R 3 = Br). Cyclodehydration of the former compounds with sulfuric acid in acetic acid gives solely 3-bromo-2-styrylchromones 34 (R 3 = Br).…”

2,3-Diarylxanthones as Potential Inhibitors of Arachidonic Acid Metabolic Pathways

“…2,3-Diarylxanthones 1-3 ( Fig. 1) were synthesized according to a previously described procedure [18].…”

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

“…[23] In 2009, 2-and 3-styrylchromones were used in cyclization reactions to afford new polyhydroxylated 2,3-diarylxanthones. [24] Following the previously described studies, 2-(4-arylbuta-1,3-dien-1-yl)chromones underwent electrocyclization and oxidation processes in order to prepare 1-arylxanthones. [25] In this paper, we disclose our synthesis of new chromone derivatives, 2-(4-arylbut-1-en-3-yn-1-yl)chromones 4a-d, which were further used as synthons to generate new xanthone-1,2,3-triazole dyads.…”