Photoprocesses of <i>p</i>-Benzoquinones in Aqueous Solution
作者:Helmut Görner
DOI:10.1021/jp030789a
日期:2003.12.1
The photochemistry of 1,4-benzoquinone (BQ) and several derivatives, for example, duroquinone, trimethyl-2,5- or 2,6-dimethyl-, and methyl-BQ in aqueous solution or mixtures with polar media, for example, acetonitrile or 2,2,2-trifluoroethanol, was studied by time-resolved UV−vis spectroscopy after pulses at 248 and 308 nm. The triplet state and the semiquinone radical (•QH/Q•-) of BQs are spectroscopically
Selective oxidation of pseudocumene and 2-methylnaphthalene with aqueous hydrogen peroxide catalyzed by γ-Keggin divanadium-substituted polyoxotungstate
作者:Olga V. Zalomaeva、Vasiliy Yu. Evtushok、Gennadii M. Maksimov、Oxana A. Kholdeeva
DOI:10.1016/j.jorganchem.2015.04.020
日期:2015.9
of a γ-Keggin divanadium-substitutedphosphotungstate, (Bu4N)4[γ-PW10O38V2(μ-O)(μ-OH)], has been evaluated in the selective oxidation of 1,2,4-trimethylbenzene (pseudocumene, PC) and 2-methylnaphthalene with the green oxidant, 35% aqueous hydrogenperoxide. Under conditions of H2O2 deficiency ([PC]/[H2O2] = 17–22), PC oxidation proceeded with unusually high chemo- and regioselectivity, producing exclusively
一个γ-的Keggin二钒取代的磷钨酸盐的催化性能,(BU 4 N)4 [γ-PW 10 ö 38 V 2(μ-O)(μ-OH)],已经在1选择氧化评价2,4-三甲基苯(拟枯烯,PC)和2-甲基萘与绿色氧化剂,35%的过氧化氢水溶液。在H 2 O 2缺乏([PC] / [H 2 O 2] = 17–22),PC氧化以异常高的化学选择性和区域选择性进行,仅生成摩尔比为7.3的2,4,5-三甲基苯酚(2,4,5-TMP)和2,3,5-TMP / 1,基于氧化剂的产率为73%。发现了痕量的异美2,3,6-三甲基苯酚。在过量的H 2 O 2([H 2 O 2 ] / [PC] = 8)的条件下,形成2,3,5-三甲基-1,4-苯醌(TMBQ,维生素E关键中间体),在41%的选择性下41%的底物转化率。在2-甲基萘的氧化中也发现非典型区域选择性,该氧化主要产生6-甲基-1,4-萘醌(6-MNQ),而
Effect of combination sequence of precursors on the structural and catalytic properties of Ti–SBA-15
The combination sequence of Ti and Si precursors (TTIP and TEOS) in the synthesis solution of Ti-incorporated SBA-15 mesoporous silica (shortly termed TiâSBA-15) was found for the first time to be critical for the distribution of tetrahedrally (Td) coordinated Ti(IV) sites in the resultant TiâSBA-15. It was found that TTIP pre-assembled with P123 in the synthesis solution for 3 h before the addition of TEOS gave Td-coordinated Ti(IV) sites predominately incorporated near the superficial regions of the framework and were highly accessible to the reactants in catalytic reactions.
Process for the production of 2,3,5-trimethylbenzoquinone
申请人:MITSUBISHI GAS CHEMICAL COMPANY, INC.
公开号:EP0127888A1
公开(公告)日:1984-12-12
A process for the production of 2,3,5-trimethyl- benzoquinone (TMBQ) from 2,3,6- trimethylphenol (TMP) is described, comprising contacting TMP with molecular oxygen in a medium of water and an aliphatic alcohol having from 4 to 10 carbon atoms in the presence as a catalyst of a copper halogeno complex represented by the general formula as shown below or a mixture of the copper halogeno complex and an alkali metal halide.
wherein M is an alkali metal or ammonium, Cu(II) is a divalent copper, X is a halogen atom, I is an integer of 1 to 3, m is 1 or 2, n is an integer of 3 to 8, p is 1 or 2, and II + 2mp = np. The present process yields various advantages; for example, TMBQ can be produced with high selectivity, and since the reaction is performed in a specific medium (the medium is heterogeneous because the alcohols are immiscible or little miscible with water) and TMBQ is soluble in the alcohol layer, while the catalyst is soluble in the water layer, TMBQ can be easily separated and reuse of the catalyst can be accomplished by a simplified procedure. TMBQ is a useful compound as an intermediate for use in the preparation of Vitamin E.
Compounds having the structural formula
which inhibit the enzymatic activity of proteolytic enzymes, and processes for preparation thereof, method of use thereof in treatment of degenerative diseases and pharmaceutical compositions thereof are disclosed.