Photochemistry. IX. Constituents of Mammea americana. XI. Synthesis of 2,5- and 4,5-dihydroxyxanthone

Abstract

offers this solution:16 5.203 (H-5), 3.745, 3.613 (H-4, /gem = (15) We are grateful to Dr. Richard S. Egan for this spectrum and solution. The ABX spectrum was calculated using laocn3 [S. Castellano and A. A. Bothner-by, J. Chem. Phys., 41, 3853 (1964) ], as modified by Mr. W. C. Bass, Abbott Laboratories.

Synthesis of Xanthones: An Overview

“…Because intermolecular acylation reactions give generally higher yields than Ullmann ether syntheses, the most prevalent strategy for xanthone synthesis is acylation, followed by cyclization to form the heterocyclic ring [for a practical comparative example see 33]. The xanthone skeleton can also be formed directly from diaryl ester by pyrolysis e) [34,35] or through the above intermediates by photo Fries rearrangement f) [36][37][38][39][40][41][42], or by Smiles rearrangement g) [43,44], strategies that emerged in the last years.…”

“…This new method was also proposed for the synthesis of highly oxygenated xanthones [84]. A systematic study of alkylation of cyclic-1,3-diketones (34) with 2-bromo-6-methoxybenzofuran-3-one (33) has led to a new method of formation of the xanthone core (Scheme 9) [85]; the intermediate (35) of the reaction then reacted with psubstituted anilines to furnish the substituted xanthone derivatives (36) shown in Scheme 9.…”

Synthesis, characterisation and metal ion binding properties of crown ethers incorporating 4,5-dioxyxanthones

“…Further purification and characterisation was possible by conversion to its known diacetate. 8 The alkylation of 4,5-dihydroxyxanthone with excess ethyl iodide in DMF with potassium carbonate provided a single detectable product, crystallising from ethanol as colourless needles, with a UV spectrum (methanol) showing maxima at 248 and 354 nm, and its IR spectrum showing a typical xanthone carbonyl stretching band at 1648 cm Ϫ1 . 1 H NMR spectroscopy confirmed the presence of ethoxy groups, and two doublets and a triplet (at 7.24, 7.30 and 7.91 ppm respectively) in the aromatic region, were consistent with the bis-O-alkylation in the anticipated 4,5-diethoxyxanthone 10.…”

Synthesis of Heterocyclic Compounds via Nucleophilic Aroylation Catalyzed by Imidazolidenyl Carbene

“…30) The first one is based on the cyclization of 2-hydroxybenzophenones, [31][32][33] and the second involves the cyclodehydration of o-phenoxybenzoic acids. [34][35][36] Our method is based on the cyclization of 2,2Ј-difluorobenzophenones 5 prepared by NHC-catalyzed aroylation of 3,4-difluoronitrobenzene (3) and fluorobenzaldehydes 4 (Chart 2).…”