Formation of Radical from Photoinduced Electron Transfer Reaction and its Application for Organic Synthesis

在本研究项目中，我们发现了以下利用光诱导单电子转移（SET）反应产生的自由基物种的区域和立体选择性合成。用烯丙基硅烷/烯丙基锡烷双官能团试剂（在同一分子中同时具有烯丙基硅烷和烯丙基锡烷官能团，并具有相同的碳-碳双键）照射α-二酮的乙腈溶液，以较好的产率合成了含烯丙基硅烷部分的α-酮基高烯丙醇。这些结果表明，双功能试剂光诱导SET反应形成的阳离子基团中的（烷基）C-Sn键而不是（烷基）C-Si键选择性断裂，生成含烯丙基硅烷基团的烯丙基自由基，并与半二酮基团偶联生成α-酮基高烯丙醇。经Mg（CO_4）_2处理后，得到顺式-亚甲基环戊烷-1，2-二醇，而经四丁基氟化铵（TBAF）处理后得到反式-1，2-二醇. 1，2-萘醌与γ-取代烯丙基锡试剂在热和光化学条件下反应生成4-烯丙基-1，2-萘醌。在两种反应条件下，烯丙基的引入具有相反的区域选择性. 1，2-萘醌与烯丙基硅烷发生光化学反应，经双自由基中间体生成[3+2]环加合物，再经三氟化硼、硝酸铈铵或TBAF处理，以中等至较高的总收率得到3-烯丙基-1，2-萘醌。

In this research project, we found the following regio-and stereo-selective synthesis using radical species produced by photoinduced single electron transfer (SET) reactions.1. Irradiation of a CH_3CN solution of a-diketones and allylsilane/allylstannane-bifunctional reagent which possesses both allylic silane and allylic stannane functionality in the same molecule sharing the same carbon-carbon double bond afforded α-ketohomoallyl alcohol having allylsilane moiety in good yields. These results indicate that the (alkyl) C-Sn bond rather than (alkyl) C-Si bond of the cation radial formed by photoinduced SET reaction of the bifunctional reagent cleavages selectively to give allylic radical having allylsilane moiety, and the resulting allylic radical couples with semidione radical to form the α-ketohomoallyl alcohol. When the treatment of the irradiated mixture with Mg(CO_4)_2 cis-methylenecyclopentane-1, 2-diols were obtained, whereas the treatment with tetrabutylammonium fluoride (TBAF) yielded trans-1, 2-diols.2. 1, 2-Naphthoquinone reacted with γ-substituted allyltin reagents in both thermal and photochemical conditions to yield 4-allyl-1, 2-naphthoquinone. The opposite regioselectivity of introduced allylic moiety was observed in both reaction conditions.3. The photochemical reaction of 1, 2-naphthoquinones with allylsilanes afforded [3+2] cycloadducts via diradical intermediate, which was converted to 3-allyl-1, 2-naphthoquinones in moderate to good overall yields by treatment with boron trifluoride, ammonium cerium nitrate or TBAF.