56002-83-6Relevant academic research and scientific papers
Rhodium-catalyzed cleavage reaction of aryl methyl ethers with thioesters
Arisawa, Mieko,Nihei, Yuri,Suzuki, Takaaki,Yamaguchi, Masahiko
supporting information; experimental part, p. 855 - 857 (2012/03/26)
A rhodium complex catalyzed the reaction of aryl methyl ethers and thioesters giving the corresponding aryl esters and methyl sulfides. S-(p-Chlorophenyl) p-(dimethylamino)benzothioate was used for the reaction of methyl aryl ethers with electron-withdrawing groups, and an S-(p-tolyl) derivative was used for those with electron-donating groups. Polymethoxybenzenes were converted to the esters in a regioselective manner.
Studies of the Selective O-Alkylation and Dealkylation of Flavonoids. XXI.: A Convenient Method for Synthesizing 3,5,7-Trihydroxy-6,8-dimethoxyflavones and 5,7-Dihydroxy-3,6,8-trimethoxyflavones
Horie, Tokunaru,Kitou, Takeshi,Kawamura, Yasuhiko,Yamashita, Kazuyo
, p. 1033 - 1041 (2007/10/03)
The Friedel-Crafts acetylation with boron trifluoride was studied and it was found that 1-(2,4-dihydroxy-3,5,6-trimethoxyphenyl)ethanone was conveniently synthesized from 2,3,5,6-tetramethoxyphenyl acetate in a mixture of acetic anhydride and acetic acid. 1-[2-Hydroxy-3,5,6-trimethoxy-4-(methoxyinethoxy)phenyl]ethanone was cyclized to 7-hydroxy-5,6,8-trimethoxyflavone by using the Baker-Venkataraman transformation. The 7-benzyl ether of the flavone was oxidized with dimethyldioxirane and then treated with a small amount of p-toluenesulfonic acid to give 7-benzyloxy-3-hydroxy-5,6,8-trimethoxyflavone, which was converted into the methyl ether and tosylate. The 5-methoxy group in the methyl ether or tosylate was selectively cleaved with anhydrous aluminum bromide in acetonitrile under mild conditions to give the corresponding 5-hydroxyflavones and the latter compound with a 3-tosyloxy group was smoothly converted into the 3,5-dihydroxyflavone by hydrolysis with potassium carbonate in methanol. The hydrogenolysis of the 7-benzyloxy-3,5-dihydroxyflavone and its 3-methyl ether afforded quantitatively 3,5,7-trihydroxy-6,8-dimethoxyflavone and its 3-methyl ether. The process was suitable as a general method for synthesizing 3,5,7-trihydroxy-6,8-dimethoxyflavones and their 3-methyl ethers and the six flavones were synthesized for the clarification of their 1H and 13CNMR, MS, and UV spectral properties.
Pulse Radiolytic Investigations of Aqueous Solutions of Methoxybenzene Cation Radicals: The Effect of Colloidal RuO2
Brandys, Marek,Sasson, Richard E.,Rabani, Joseph
, p. 953 - 962 (2007/10/02)
The formation and decay of the radical cations of 1,4-dimethoxybenzene (DMB) and 1,2,4,5-tetramethoxybenzene (TMB) were investigated by the pulse radiolysis technique in the absence and the presence of colloidal RuO2 particles.DMB2. was obtained only by T12+ oxidation of DMB while TMB+.+ was produced by oxidation of TMB using both T12+ and Br2-.In the absence of RuO2 both DMB.+ and TMB.+ decay predominantly via a second-order process, although there is a contribution of a pseudo-first-order reaction.The rate constants for these reactions are reported.RuO2 colloidal particles catalyze the decay of both TMB.+ and DMB.+.The reactions of TMB.+ with RuO2 were found to depend on pH, pulse intensity, and colloidal concentration.At pH 3-4, adsorbtion of TMB.+ to the colloid is observed, followed by the decay of the remaining TMB.+ in the bulk.At higher pHs, loading of the RuO2 colloid by positive holes takes place until equilibrium is archieved between loaded holes and TMB.+ and again the remaining TMB.+ decays at a later stage.The fraction of TMB.+ that loads the colloidal particles increases with both pH and .It is also suggested that DMB.+ loads the RuO2 at the pH where experiments were performed. (TMB)2 and (DMB)2 dimers (or higher oligomers) are suggested to be the final products both in absence and presence of RuO2.No O2 is formed with the RuO2 colloid despite a favorable redox potential for water oxidation.
