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。一个是与光诱导电子转移(PET)化学有关的，另一个是与二碘化钐(SMI_2)化学有关的。研究了二苯甲酮类化合物与1，3-二甲基-2-烯基苯并咪唑啉(DMPBI)或2-(2‘-hydrohyphenyl)-1，3-dimethylbenzimidazoline(HPDMBI)的PET反应，发现它们的自由基阳离子发生了区域选择性的去质子化反应。也就是说，DMPBI的自由基阳离子给二苯甲酮酮自由基提供了C_2位的质子，而o-HPDMBI的自由基阳离子给出了苯酚质子。在与上述化合物及相关的苯并咪唑类化合物的PET还原反应中，电子供体的吡喃比相应的菲是更可靠的敏化剂。研究了2-卤甲基-2-(3-丁烯基)取代环酮与胺供体的正电子发射光谱，提出了正电子对苯二甲酸乙二醇酯生成的酮基不会发生…亲核取代反应。同一分子中碳-卤键较远的单电子转移较多。为了扩大SMI_2促进的酮-酯偶联反应的通用性，人们将SMI_2与烷氧基甲酰基取代酮、酰氧基取代酮或含碳酸酯基团的酮进行反应，得到了预期的环状化合物。值得注意的是发现了涉及环丙醇衍生物的还原形成和氧化开环的新的环化和扩环反应。例如，通过适当的氧化剂处理，某些γ-酮酸酯与SMI2反应产生的环丙酚被转化为苯并三氮杂环丙酮。此外，还研究了α-溴甲基取代环酮分子内Sm-Barbier反应得到的环丙醇衍生物的氧化反应。值得注意的是，成功地进行了这些顺序还原和氧化过程的一锅反应。最后，发现环丙基硅醚的区域选择性开环反应依赖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，并将努力开发新型的基于电子转移的功能分子和分子体系。较少

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