Heterocyclic syntheses with β‐ketosulfoxides. I. New syntheses of chromones, flavones, thioindigo and thioflavones

Abstract

Sir:1 his communication is the first of a series concerned with the synthetic uses of ortho-substituted 0-ketosulfoxides. In particular, it deals with new syntheses of chromones, flavones, thioflavones and thioindigo.Extension of our work on the addition of dimethyl-

Diversity-Oriented Synthesis of Natural-Product-like Libraries Containing a 3-Methylbenzofuran Moiety for the Discovery of New Chemical Elicitors

“…These transformations have involved the Baker–Venkataraman rearrangement, Allan–Robinson reaction, and the intramolecular cyclization of 2‐hydroxychalcones . We tried to use the Von Strandtmann approach for constructing 4‐pyrone rings . The 3‐methylbenzofuran 9 was treated with the dimsyl anion in DMSO to form the β‐ketosulfoxide 13 , which after treatment with benzaldehyde derivatives and piperidine in anhydrous toluene, first at 40 °C and then at 110 °C, produced the corresponding 3‐methylfuranoflavones 14 (Table ).…”

The synthesis and biological activity of novel anthracenone-pyranones and anthracenone-furans

“…DMEDA is N,N 0 -dimethylethylenediamine. Compounds 4,9,[13][14][15][16]23,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] have been prepared and characterised previously. 21 Non-1-yn-3-one (10) was prepared according to the procedure by Braddock et al 52 3.1.1.…”

“…21,[27][28][29] Eventually this intermediate 13 was also used en route to the natural product (±)-BE-26554A (4) (Scheme 2). 21 The b-keto-sulfoxide-annulation procedure with propionaldehyde was especially high yielding (81%) which provided the impetus to expand this reaction to other aldehydes.…”

The Total Synthesis of Heraclemycin B through β‐Ketosulfoxide and Aldehyde Annulation

“…Alternatively protonation of the alcohol within 22 followed by cyclisation and the elimination of water could also be responsible for the formation of intermediate 23 . The final step involves elimination of methane sulfenic acid resulting in the 4‐pyranone ring as proposed by others in the literature …”