Type B semiconductor photocatalysis: The synthesis of homoallyl amines by cadmium sulfide-catalyzed linear photoaddition of olefins and enol/allyl ethers to N-phenylbenzophenone imine
Type B semiconductor photocatalysis: The synthesis of homoallyl amines by cadmium sulfide-catalyzed linear photoaddition of olefins and enol/allyl ethers to N-phenylbenzophenone imine
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DOI：
10.1002/chem.19970031013
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发表时间：
1997-10-01
影响因子：
4.3
通讯作者：
Kisch, H
中科院分区：
文献类型：
--
作者：
Keck, H;Schindler, W;Kisch, H
以N-苯基二苯甲酮亚胺为催化剂，分别与环己烯、2，3-二氢呋喃、2，5-二氢呋喃、3，4-二氢吡喃、2-戊烯、环戊烯、1-甲基环己烯、α-蒎烯在可见光照射下合成了高烯丙基胺。最后三种烯烃的产物的结构通过单晶X-射线分析确定，以证明亚胺的C-烷基化已经发生，因此，该反应形式上是亚胺插入烯烃的烯丙基C-H键，提出了光生电子-空穴对将亚胺还原成α-氨基甲酸酯。氨基二苯基甲基自由基，并将烯烃氧化，伴随去质子化成相应的。这些中间体的杂偶联提供了最终的加成产物，因此整个反应被归类为B型半导体加成反应。乙酸的存在通过使亚胺的还原电位更正来加速反应。在2，5-二氢呋喃/环戊烯/3，4-二氢吡喃系列中，随着烯烃氧化的驱动力的增加，表观量子产率的降低指向二次反电子转移的显著贡献。
Homoallyl amines were synthesized by visible-light irradiation of CdS powder in the presence of N-phenylbenzophenone imine and cyclohexene, 2,3-dihydrofuran, 2,5-dihydrofuran, 3,4-dihydropyran, 2-pentene, cyclopentene, 1-methylcyclohexene, or alpha-pinene. The structures of the products from the last three olefins were determined by single-crystal X-ray analysis to prove that C-alkylation of the imine had occurred, Thus, the reaction is formally an insertion of the imine into an allylic C-H bond of the olefin, It is proposed that a photogenerated electron-hole pair reduces the imine to an alpha-aminodiphenylmethyl radical and oxidizes the olefin with concomitant deprotonation to the corresponding. allyl radical, Heterocoupling of these intermediates affords the final addition product, The overall reaction is therefore classified as type B semiconductor photocatalysis. The presence of acetic acid accelerates the reaction by rendering the reduction potential of the imine more positive, In the series 2,5-dihydrofuran/cyclopentene/3,4-dihydropyran, the decrease in apparent quantum yield with increasing driving force of olefin oxidation points to a significant contribution of secondary back electron transfer.