Control of the Reactivity of Ketyl Radicals through Acid-Base Interaction with Proton and Metal Ions

我们调查了两个主要的研究课题。一个与光致电子转移（PET）化学有关，另一个与二碘化钐（SmI_2）化学有关。研究了二苯甲酮类化合物与1,3-二甲基-2-对苯基苯并咪唑啉（DMPBI）和2-（2′-羟基苯基）-1,3-二甲基苯并咪唑啉（HPDMBI）的PET反应，发现它们的自由基阳离子发生了区域选择性去质子化。即DMPBI的自由基阳离子给二苯甲酮基一个C_2位质子，而o-HPDMBI的自由基阳离子给苯酚一个C_2位质子。在与上述和相关的苯并咪唑类化合物合作的某些羰基化合物的PET还原反应中，发现给电子芘比相应的蒽类更可靠。对2-卤甲基-2-（3-丁烯基）取代环酮与胺供体的PET反应的研究使我们提出PET生成的基自由基不发生亲核取代，而是与同一分子中的远碳-卤素键进行单电子转移。通过SmI_2与烷氧羰基取代酮、无环氧基取代酮或含碳酸盐基团的酮的反应，扩大了SmI_2促进的分子内酮-酯偶联反应的通用性，得到了预期的环状化合物。在环丙醇衍生物的还原形成和氧化开环过程中发现了新的环化和扩环反应。例如，某些γ-酮酯与SmI_2反应生成的环丙酚经适当的氧化剂处理后可转化为苯并唑波酮。研究了α-溴甲基取代环酮分子内钐Barbier反应生成的环丙醇衍生物的氧化反应。值得注意的是，这些连续的还原和氧化过程都成功地进行了一锅反应。最后，发现了环丙基硅醚的区域选择性开环反应，这取决于所采用的电子转移条件。我们将进一步对上述电子转移体系进行机理研究，以实现对反应途径的精细控制，并尝试开发新型的基于电子转移的功能分子和分子体系。少

We have investigated two major research subjects. One is related to photoinduced electron-transfer (PET) chemistry, and the other is related to samarium diiodide (SmI_2) chemistry. PET reactions of benzophenones with 1,3-dimethyl-2-pehnylbenzimidazoline (DMPBI) or 2-(2'-hydrohyphenyl)-1,3-dimethylbenzimidazoline (HPDMBI) were investigated, and then regioselective deprotonation of their radical cations were discovered. Namely, the radical cation of DMPBI donates a proton at C_2 position to the benzophenone ketyl radicals while the radical cation of o-HPDMBI donates a phenol proton. Electron-donating pyrenes were found to be more reliable sensitizers than the corresponding anthracenes in the PET reductions of certain carbonyl compounds cooperating with above and related benzimidazolines. Investigation of PET reaction of 2-halomethyl-2-(3-butenyl) substituted cyclic ketones with amine donors allowed us to propose that PET generated ketyl radicals do not undergo nucleophilic substitution b … More ut single electron transfer with distant carbon-halogen bonds in the same molecules. Reactions of SmI_2 with alkoxy carbonyl substituted ketones, acycloxy substituted ketones, or ketones possessing carbonate moieties were conducted to expand the versatility of SmI_2 promoted intramolecular ketone-ester coupling reactions, and the expected cyclic compounds were often obtained. Discovery of novel cyclization and ring-expansion reactions involving reductive formation and oxidative ring-opening of cyclopropanol derivatives was noteworthy. For example, cyclopropnaols derived from the reactions of certain γ-keto esters with SmI_2 were converted to benzotropolones by the treatment with appropriate oxidants. Also, oxidation reactions of cyclopropanol derivatives obtained from intramolecular samarium Barbier reactions of α-bromomethyl substituted cyclic ketones were studied. Notably, one-pot reactions of these sequential reduction and oxidation processes were successfully performed. Finally, regioselective ring-opening reactions of cyclopropyl silyl ethers depending on the electron transfer conditions employed were discovered. We will further conduct mechanistic investigations of above electron-transfer systems to achieve fine-control of the reaction pathways, and will try to exploit new types of electron-transfer based functional molecules and molecular systems. Less