Microwave-Assisted Efficient and Green Synthesis of Hydroxyxanthone in Water

Abstract

An efficient and green procedure has been developed for the synthesis of hydroxyxanthones from substituted 2,2 0 -dihydroxybenzophenone precursors via microwave-assisted base-catalyzed cyclization in water. This method provides excellent yields of products in a short time, making it a useful strategy for the synthesis of structurally diverse hydroxyxanthones.

Biotransformation of guttiferones, Symphonia globulifera metabolites, by Bipolaris cactivora, an endophytic fungus isolated from its leaves

“…During the biotransformation, the residual metabolism may modify pH, in particular in buffer with relatively low concentration, with its increase or decrease depending on the microorganisms. However, to the extent that such cyclization was observed for benzophenone under certain conditions (basic pH, 100°C) 33…”

Recent advances in the synthesis of xanthones and azaxanthones

“…The approach used by Langer and Appel 182 consisted of the condensation of 1,3bis-silyl enol ethers (141), unsymmetrical acetoacetone, with 3-cyanobenzopyrylium triflates (140). This yielded an openchained product (142), which was treated with triethylamine, to give an azaxanthone (143) in 46% overall yield, through a domino "retro-Michael-lactonization-aldol" reaction (Scheme 20C).…”

Xanthones and Cancer: from Natural Sources to Mechanisms of Action

“…Aminoxanthones Selective amination, ketone-assisted, ruthenium-catalyzed [161,162] Amphiphilic xanthone Condensation of phloroglucinol and 2,4,6-trihydroxybenzoic acid in the presence of Eaton's reagent [163,164] Annulated xanthones Heck reaction/double CÀ H activation/retro-DielsÀ Alder [165] Azaxanthones Regioselective, Copper catalyzed, Ullmann coupling [166][167][168][169] Benzophenone xanthones…”

“…From salicylic acid and phenol in phosphorus pentoxide-methanesulfonic acid [144,170] Benzoxanthone FeCl 3 -Catalyzed, three-components, one-pot [171] Caged xanthones Regioselective Claisen/DielsÀ Alder cascade reaction [151,[172][173][174]175] Haloxanthones From 2-bromofluorobenzenes and salicylaldehydes via palladium-catalyzed acylation-SNAr [167,176,177] Hydroxyxanthone Classical one-step synthesis starting from two aryls induced by Mannich reaction and Eaton's reagents. [167,[178][179][180][181][182] Pyranoxanthones From 1,3-dihydroxyxanthone with different reagents [180] Pyridyl xanthones Ag 2 CO 3 mediated oxidative cyclization [183] Sulfonamides xanthones Eaton's reagent and chlorosulfonic acid [184] Thioxanthones Heteropoly acid, catalytic, under microwave [176,185,186] Toxyloxanthones Regioselective aryne addition and Claisen rearrangement [187] Triazole xanthone…”