A mild thermal and acid-catalyzed rearrangement of O-aryl ethers into ortho-hydroxy arenes.
TL;DR: The exploration of this rearrangement of an O-aryl ether to an ortho-hydroxyaryl system under mild thermal and both Brønsted and Lewis acid-catalyzed conditions is discussed.
About: This article is published in Organic Letters.The article was published on 2005-08-27. It has received 34 citations till now. The article focuses on the topics: Ether & Aryl.
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TL;DR: From 2 to 1!
Abstract: From 2 to 1! Racemic tertiary halooxindoles proceed to enantioenriched oxindoles bearing all-carbon quaternary stereocenters as a result of a catalytic enantioselective stereoablative process (see scheme). The application of this procedure allows for the rapid asymmetric construction of biologically significant alkaloid core motifs.
175 citations
TL;DR: This review details the synthetic studies on this fascinating natural product starting from early studies on the original structure, through the synthesis of the originally proposed structure and the subsequent structural revision, to the eventual successful syntheses of the natural product itself.
94 citations
TL;DR: A Lewis acid catalyzed Friedel-Crafts reaction of electron rich aromatics with 3-alkyl-3-hydroxy-2-oxindole with a straightforward access to the core of azonazine sharing an all-carbon quaternary stereocenter at the tetracyclic ring junction.
66 citations
TL;DR: An unusual O-aryl into C-aryl rearrangement was discovered that allows partial control of the absolute stereochemistry of the C-10 quaternary stereogenic center and is sensitive to the protecting group on both the tryptophan nitrogen atom and the tyrosine nitrogen atom.
Abstract: During the course of studies on the synthesis of diazonamide A 1, an unusual O-aryl into C-aryl rearrangement was discovered that allows partial control of the absolute stereochemistry of the C-10 quaternary stereogenic center. Treatment of 30 with TBAF/THF gave the O-tyrosine ethers 31 and 32 (1:1), which on heating each separately in chloroform at reflux rearranged to 33 and 34 in ratios of 84:16 and 56:44, respectively. This corresponds to a 70% yield of the correct C-10 stereoisomer 33 and a 30% yield of the wrong C-10 stereoisomer 34. Attempts to convert 34 into 33 by ipso-protonation and equilibration were unsuccessful. Confirmation of the stereochemical outcome of the rearrangement was obtained by converting 33 into 37, an advanced intermediate in the first synthesis of diazonamide A by Nicolaou et al. It was also found that the success of the above rearrangement is sensitive to the protecting group on both the tryptophan nitrogen atom and the tyrosine nitrogen atom.
65 citations
TL;DR: The Hofmann-Martius rearrangement of 3-N-aryl-2-oxindoles into 3-(arylamino)-2- oxindoles under thermal and acid-catalyzed conditions is described.
57 citations
References
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TL;DR: In this article, a solution of lithium hexamethyldisilazide in THF (1, 0.20 mL,0.20 mmol) was added dropwise to a solution 1 (0.038 g; 0.5 mL) at 78C.
Abstract: Representative procedure for the preparation of 7: A solution of lithium hexamethyldisilazide in THF (1, 0.20 mL, 0.20 mmol) was added dropwise to a solution of 1 (0.038 g; 0.20 mmol) in THF (0.5 mL) at 78C. The resulting pale yellow solution was stirred for 10 min at the same temperature, and then a solution of coumarin 2b (0.032 g; 0.22 mmol) in THF (0.5 mL) was added dropwise at 78C. After 30 min, a solution of trans chalcone 5c (0.045 g, 0.22 mmol) was added dropwise. The reaction mixture was stirred for a further 30 min at the same temperature, and then a solution of trimethylsilyl chloride (0.31 mL) in methanol (5 mL) was added at 78C. The reaction mixture was warmed to room temperature overnight. The solvents were removed in vacuo to give the crude product, which was purified by column chromatography (1:1 petroleum ether/ethyl
142 citations
TL;DR: In this paper, the primary reactions between radicals and organic molecules are discussed from the point of view of a principle which states that there shall be least change in atomic position and least changes in electronic configuration during an elementary reaction, and it is concluded that alkyl radicals will attack most easily exposed positive atoms, i.e., in organic molecules, the hydrogen atoms.
Abstract: The primary reactions between radicals and organic molecules are discussed from the point of view of a principle which states that there shall be least change in atomic position and least change in electronic configuration during an elementary reaction. We have concluded that alkyl radicals will attack most easily exposed positive atoms, i.e., in organic molecules, the hydrogen atoms. The attack on exposed negative atoms such as N, O or Cl is less probable whereas a completely shielded carbon atom should certainly not be attacked in the primary step. A doubly or triply bonded carbon atom can, however, react with a radical. These statements are discussed from the experimental point of view, together with the question as to when it is necessary to assume that organic reactions proceed through radical chains.
126 citations
TL;DR: This powerful approach provides easy and stereoselective access to polycyclic hydroquinolines, as shown for an example in Equation (1).
Abstract: Surprisingly, thesimplestmethodpossibleforo-azaxylyleneproduction, base-induced elimination of hydrogen chloride from amide or sulfonamide derivatives of o-(chloromethyl)aniline, has never been reported. This powerful approach provides easy and stereoselective access to polycyclic hydroquinolines, as shown for an example in Equation (1).
112 citations
TL;DR: The diphenyloxindole showed mechanism-specific antiproliferative activity that was comparable to known translation initiation inhibitors such as clotrimazole or troglitazone and identified as a lead compound for Ca2+-depletion-mediated inhibition of translation initiation.
Abstract: A series of substituted 3,3-diphenyl-1,3-dihydro-indol-2-ones was synthesized from the corresponding isatins. The compounds were studied for cell growth inhibition mediated by partial depletion of intracellular Ca2+ stores that leads to phosphorylation of eIF2α. The diphenyloxindole (1) showed mechanism-specific antiproliferative activity that was comparable to known translation initiation inhibitors such as clotrimazole or troglitazone. SAR studies identified m‘-tert-butyl and o-hydroxy substituted diphenyloxindole (25) as a lead compound for Ca2+-depletion-mediated inhibition of translation initiation.
94 citations
27 citations