Highly efficient palladium-catalyzed Suzuki–Miyaura reactions of potassium aryltrifluoroborates with 5-iodo-1,3-dioxin-4-ones in water: an approach to α-aryl-β-ketoesters
摘要:
The high efficient palladium-catalyzed Suzuki-Miyaura reactions of potassium aryltrifluoroborates 3 with 5-iodo-1,3-dioxin-4-ones 2a-b in water as only solvent in the presence of n-Bu4NOH as base is reported. The respective 5-aryl-1,3-dioxin-4-ones 4a-n were obtained in good to excellent yields. The catalyst system provides high efficiency at low load using electronically diverse coupling partners. The obtained 2,2,6-trimethyl-5-aryl-1,3-dioxin-4-ones were transformed into corresponding alpha-aryl-beta-ketoesters 6 by reaction with an alcohol in the absence of solvent. (C) 2009 Elsevier Ltd. All rights reserved.
Disclosed are novel 5-halo-4H-1,3-dioxin-4-ones and their preparation by treating a compound having the formula ##STR1## with X.sub.2 or SO.sub.2 X.sub.2 wherein X is Cl or Br.
Disclosed is a process for the preparation of .alpha.-haloacetoacetic esters by the reaction of an alkali metal alkoxide with a 5-halo-4H-1,3-dioxin-4-one compound, the desired product being obtained as an alkali metal salt which may be converted to the corresponding free ester by treating with acid.
[EN] 5-HALO-4H-1,3-DIOXIN-4-ONE COMPOUNDS, alpha -HALO-ACETOACETIC ESTERS PREPARED FROM SUCH COMPOUNDS AND PROCESS FOR THEIR PREPARATION
申请人:EASTMAN KODAK COMPANY
公开号:WO1986000068A1
公开(公告)日:1986-01-03
(EN) 5-halo-4H-1,3-dioxin-4-ones and their preparation by treating a compound having formula (I), with X2 or SO2X2 wherein X is Cl or Br. The 5-halo-4H-1,3-dioxin-4-ones can then be reacted with an alkali metal alkoxide at a temperature of about -40oC. to about 50oC. to provide an $g(a)-haloaceto-acetic ester.(FR) L'invention concerne des 5-halo-4H-1,3-dioxine-4-ones et leur préparation en traitant un composé ayant la formule (I) avec X2 ou SO2X2, dans laquelle X représente Cl ou Br. Il est alors possible de faire réagir les 5-halo-4H-1,3-dioxine-4-ones avec un alkoxide de métal alcalin à une température d'environ -40oC jusqu'à environ 50oC, afin d'obtenir un ester $g(a)-haloacétoacétique.
Bromination of 2,2,6-trialkyl-1,3-dioxan-4-ones. Application of the deuterium isotope effect to the synthesis of a chiral trialkyldioxinone
作者:Gordon L. Lange、Michael G. Organ、Michael R. Roche
DOI:10.1021/jo00048a039
日期:1992.10
Free-radical bromination (2 equiv of NBS) of 2-tert-butyl-2,6-dimethyl-1,3-dioxan-4-one (6a) gives the 2-bromomethyl product 7a. By contrast, bromination of 2-tert-butyl-2-methyl-1,3-dioxan-4-one (1) is reported to occur at the 6-position. Deuterium-labeling experiments established that 7a is formed by direct substitution at the 2-methyl group of 6a and not by abstraction of H-6 followed by hydrogen atom transfer from the 2-methyl group and bromination of the resultant primary radical 12. When 2-tert-butyl-6-methyl-2-(methyl-d3)-1,3-dioxan-4-one (13) is reacted with 4 equiv of NBS, the course of the reaction is altered dramatically and the major product formed in high yield is dioxinone 16. Thus, a trideuteriomethyl group directs bromination away from the 2-methyl site to H-6. Bromination at the 6-position followed by loss of HBr, addition of Br2, and loss of a second HBr gives 16. Dioxinone 14, a valuable substrate for asymmetric induction studies, is formed in high yield by reductive debromination of 16. When (R)-3-hydroxybutyric acid is used in the preparation of 13, optically pure (-)-14 is obtained using the sequence described.