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

在本研究项目中，我们利用光诱导单电子转移(SET)反应产生的自由基物种，发现了以下区域和立体选择性的合成。α-二酮和烯丙基硅烷/烯丙基锡烷-双官能团试剂在同一分子中具有相同的碳-碳双键同时具有烯丙基硅烷和烯丙基锡烷官能团的CH_3CN溶液辐射，以较好的产率得到了具有烯丙基硅烷部分的α-酮高烯丙基醇。这些结果表明，双官能团试剂的光诱导SET反应形成的阳离子径向的(烷基)C-Sn键而不是(烷基)C-Si键选择性地裂解生成具有烯丙基硅烷基团的烯丙基自由基，生成的烯丙基自由基与半二酮自由基偶联生成α-酮高烯丙基醇。经辐照的混合物用Mg(CO4)2处理得到顺式亚甲基环戊烷-1，2-二醇，而用四丁基氟化铵(TBAF)处理得到反式-1，2-二醇。1，2-萘醌与γ取代的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，均观察到引入的烯丙基部分具有相反的区域选择性。1，2-萘醌与烯丙基硅烷的光化学反应生成[3+2]环加成物，再用三氟化硼、硝酸铈铵或TBAF处理，以中等或较好的总收率转化为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.