Janus-faced 5-methyl group in 2-hydroxy-5-methyl-[1,4]-benzoquinone
作者:Thomas Rosenau、Nele Sophie Zwirchmayr、Takashi Hosoya、Andreas Hofinger-Horvath、Markus Bacher、Antje Potthast
DOI:10.1016/j.tet.2017.09.038
日期:2017.11
Under alkaline/basic conditions, the 5-methylgroup is deprotonated, this time performing as carbanion equivalent being once more stabilized by resonance. This facet of reactivity was used for instance in regioselective perdeuteration of the 5-methyl position or in Michael additions. The reaction medium is thus able to govern the chemical behavior of the 5-methylgroup, to effect its umpoling and to switch
The Pd(PPh3)4-catalyzed reaction of 2-hydroxy-1,4-naphthoquinone (lawsone) with allyl alcohols and allyl esters offers an easy access to 3-allyl-2-hydroxy-1,4-naphthoquinones, compounds with interesting biological activity. The reaction finds application in the preparation of lapachol. Other 2-hydroxy-1,4-benzoquinones give allylation products in low yields.
Oxidative chemistry of the natural antioxidant hydroxytyrosol: hydrogen peroxide-dependent hydroxylation and hydroxyquinone/o-quinone coupling pathways
作者:Maria De Lucia、Lucia Panzella、Alessandro Pezzella、Alessandra Napolitano、Marco d'Ischia
DOI:10.1016/j.tet.2005.10.055
日期:2006.2
Similar oxidation of 4-methylcatechol gave, after the same work-up, the acetylated derivatives of 1,2,4-trihydroxy-5-methylbenzene (5) and the pentahydroxybiphenyl 6. Mechanistic experiments suggested that hydrogen peroxide affects the course of the oxidation of 1 by adding to the first formed o-quinone to give a hydroxyquinone intermediate. This could bring nucleophilic attack to the o-quinone of 1 to
在pH 7.4的磷酸盐缓冲液中用过氧化物酶/ H 2 O 2氧化天然抗氧化剂羟基酪醇(1)导致形成两种主要的可乙酸乙酯萃取的产物。这些可以通过还原和乙酰化后的制备TLC分离,并且通过2D NMR和MS分析鉴定为2-(2,4,5-三羟基苯基)乙醇(3)的四乙酰基衍生物和五羟基联苯4的七乙酰基衍生物。经过相同的后处理,4-甲基邻苯二酚的类似氧化反应得到1,2,4-三羟基-5-甲基苯的乙酰化衍生物(5)和五羟基联苯6。机械实验表明,过氧化氢的影响的氧化过程1通过向第一形成Ò -quinone,得到羟基醌中间体。这可能对1的邻醌产生亲核攻击,从而使二聚体4形成。这些结果揭示了4-烷基邻苯二酚的新型氧化途径,并为研究1的抗氧化作用机理提供了改进的化学基础。
Generation of the Neurotoxin 6-Hydroxydopamine by Peroxidase/H2O2 Oxidation of Dopamine
the tyrosinase/O2 system or chemical agents such as periodate or ferricyanide. These and other data suggest that, under the conditions adopted, nucleophilic attack of the hydrogen peroxide anion on DQ leading to TQ significantly competes with the intramolecularcyclization path. In line with this mechanism, the reaction course was not affected by the presence of hydroxyl radical scavengers. Peroxidase/H2O2
The chemistry of hydroxy-quinones. Part IV. The reaction of 2,6-dihydroxy-benzoquinones with alkali
作者:John F. Corbett
DOI:10.1039/j39670002408
日期:——
The alkaline degradation of C-alkylated 2,6-dihydroxy-benzoquinones has been shown to involve a benzilic acid rearrangement, followed by decarboxylation of the resulting hydroxydioxocyclopentanecarboxylic acid to give a corresponding 4-hydroxycyclopentane-1,3-dione. Kinetic data for the reaction are reported.