SEMICONDUCTOR-CATALYZED PHOTOADDITION OF OLEFINS AND ENOL ETHERS TO 1,2-DIAZENES - A NEW ROUTE TO ALLYLHYDRAZINES
SEMICONDUCTOR-CATALYZED PHOTOADDITION OF OLEFINS AND ENOL ETHERS TO 1,2-DIAZENES - A NEW ROUTE TO ALLYLHYDRAZINES
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DOI：
10.1002/chem.19950010709
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发表时间：
1995-10-01
影响因子：
4.3
通讯作者：
KISCH, H
中科院分区：
文献类型：
--
作者：
KUNNETH, R;FELDMER, C;KISCH, H
硫化锌或硫化镉粉末在质子化溶剂中的悬浮液催化烯醇醚和烯烃与1，2-二芳基和1-芳基-2-烷基-1，2-二氮的线性加成反应，生成烯丙基肼衍生物。当1，2-二氮烯较难还原时，相对量子产率急剧下降，而它们与烯醇醚/烯烃的氧化电位之间的关系是复杂的。还原为1，2-二芳基肼和伴随的烯醇醚的脱氢二聚作为副反应发生。当使用镀铂(5mol%)的光催化剂时，有利于提高光强度，并成为主要的反应途径。提出了质子耦合电子转移中的光生电子-空穴对将二氮烯还原为肼自由基，并将烯烃/烯醇醚氧化为自由基阳离子。后者通过去质子化得到的烯丙基与肼自由基发生C-N偶联反应，得到烯丙基肼。二芳基肼的形成是通过肼自由基的歧化或通过连续的质子偶联还原来实现的。因此，光加成过程可以归类为1E(-)/1h(+)过程，而2E(-)/2h(+)过程是还原所必需的。
Suspensions of zinc or cadmium sulfide powders in a protic solvent catalyse the linear addition of enol ethers and olefins to 1,2-diaryl- and 1-aryl-2-alkyl-1,2-diazenes, producing allylhydrazine derivatives. Relative quantum yields decrease sharply when the 1,2-diazene is more difficult to reduce, while their relationship to the oxidation potential of the enol ether/olefin is complicated. Reduction to 1,2-diarylhydrazine and concomitant dehydrodimerization of the enol ether occurs as a side reaction. It is favoured by increasing light intensity and becomes the major reaction path when platinized (5 mol%) photocatalysts are employed. It is proposed that the photogenerated electron - hole pair in a proton-coupled electron transfer reduces the diazene to a hydrazyl radical and oxidizes the olefin/enol ether to a radical cation. The allylic radical obtained from the latter by deprotonation then undergoes C-N coupling with the hydrazyl radical to afford the allylhydrazine. Diarylhydrazine Formation occurs by disproportionation of the hydrazyl radical or by a successive proton-coupled reduction. Thus photoaddition can be classified as a 1e(-)/1h(+) process while 2e(-)/2h(+) are necessary for the reduction.