ELECTRON-TRANSFER INDUCED PHOTOISOMERIZATION, DIMERIZATION, AND OXYGENATION OF TRANS-ANETHOLE AND CIS-ANETHOLE - THE ROLE OF MONOMER AND DIMER CATION RADICALS
ELECTRON-TRANSFER INDUCED PHOTOISOMERIZATION, DIMERIZATION, AND OXYGENATION OF TRANS-ANETHOLE AND CIS-ANETHOLE - THE ROLE OF MONOMER AND DIMER CATION RADICALS
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DOI：
10.1021/ja00234a014
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发表时间：
1988-12-21
影响因子：
15
通讯作者：
KOJIMA, M
中科院分区：
文献类型：
--
作者：
LEWIS, FD;KOJIMA, M
在电子受体存在下，反式或间茴香脑的辐照导致顺式、反式异构化、环二聚化和（在氧存在下）氧化裂解。这些反应中的每一个的初始步骤是光诱导电子转移以产生单线态自由基离子对。茴香脑阳离子自由基是每个反应中形成的初始反应中间体。通过反向电子转移发生异构化，产生三重态茴香脑，其衰变为顺式和反式异构体的混合物。二聚化通过阳离子自由基和中性基团的[2+ 1]环加成发生，其继续保持烯烃构型以产生顺式和反式头对头二聚体的混合物。顺式/反式二聚体比率对反应条件敏感，因为顺式相对于反式二聚体阳离子自由基的稳定性较低。单体阳离子自由基与O2或O2的反应导致对茴香醛的形成。无环1，4-阳离子自由基不太可能是任何观察到的产物的前体。
Irradiation of trans-or m-anethole in the presence of electron acceptors results in cis, trans isomerization, cyclo-dimerization, and (in thepresence of oxygen) oxidative cleavage. The initial step in each of these reactions is photoinduced electron transfer to yield a singlet radical ion pair. Anethole cation radicals are the initial reactive intermediates formed in each reaction. Isomerization occurs via reverse electron transfer to generate triplet anethole which decays to a mixture of cis and trans isomers. Dimerization occurs via the [2+ 1] cycloaddition of a cation radical and a neutral which proceeds with retention of olefin configuration to yield a mixture of syn and anti head-to-head dimers. The syn/anti dimer ratio is sensitive to reaction conditions because of the lower stability of the syn vs anti dimer cation radical. Reaction of the monomer cation radical with 02" or 02 results in formation of p-anisaldehyde. It is unlikely that an acyclic 1, 4-cation radical is the precursor of any of the observed products.