FENTONS REAGENT .5. HYDROXYLATION AND SIDE-CHAIN CLEAVAGE OF AROMATICS
FENTONS REAGENT .5. HYDROXYLATION AND SIDE-CHAIN CLEAVAGE OF AROMATICS
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DOI：
10.1021/ja00835a024
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发表时间：
1975-01-01
影响因子：
15
通讯作者：
JOHNSON, RA
中科院分区：
文献类型：
--
作者：
WALLING, C;JOHNSON, RA
考察了苯、甲苯、苯乙酸和苯基取代醇与Fenton试剂的反应产物。结果随着H+、Fe2+、Fe3+、Cu2+和OJ浓度的不同而变化很大，与羟基自由基加到芳香族体系中，生成的羟基环己二烯自由基可能二聚，被氧化为苯酚，或经历可逆酸催化塌缩为自由基阳离子的方案一致。这些又可以被Fe2+还原为起始物质，或者，在可能的情况下，可以进行侧链断裂(用甲苯和苯乙酸生成苯基自由基)，然后进行二聚反应或进一步氧化。酚类产物的异构体分布取决于存在的氧化剂，而与Fe3+形成的偏异构体的低产率归因于电子转移形成的中间羟基环己二烯阳离子的重排。通过选择合适的反应条件，苯乙酸可直接氧化生成苯酚、联苯或苯甲醇，选择性为81-94%，在高浓度Cu2+存在下，所有体系均以苯酚为主。
The reaction products of benzene, toluene, phenylacetic acid, and phenyl substituted alcohols with Fenton’s re-agent have been examined. Results vary widely with concentrations of H+, Fe2+, Fe3+, Cu2+, and Oj and are consistent with a scheme in which hydroxyl radicalsadd to the aromatic system, and the resulting hydroxycyclohexadienyl radicals may dimerize, be oxidized to phenols, or undergo a reversible acid-catalyzed collapse to radical cations. These, in turn may be re-duced to starting material by Fe2+ or, when possible, may undergo side-chain cleavage (with toluene and phenylacetic acid to benzyl radicals) followed by dimerization or further oxidation. Isomer distributionsof phenolic productsdepend upon the oxidizing agents present, and the low yield of meta isomersobtained with Fe3+ is ascribed to rearrangement of intermediate hydroxycyclohexadienyl cations formed by electron transfer. Oxidation of phenylacetic acid may be directed to give phenols, bibenzyl, or benzyl alcohol with 81-94% selectivity by suitable choice of reaction conditions, and all systems gave phenols as major products in the presence of high concentrations of Cu2+.