Chemo, regio, and stereoselective photo-oxygenations: Conformational and substituent effects, biomass valorization, and applications in photomicroreactors

该项目涉及开发新的底物类别、反应条件、微反应器设置以及单线态氧的光氧化过程的后续反应。我们希望研究构象控制对环己烯衍生物在Schenck-ene氧化反应中的反应活性和选择性的影响。合成、理论和操作相结合的努力将引入新的环己烯，它们在温和的条件下进行高度选择性的双氧化。机理研究将致力于双环烯和环烯芳烃中的取代基效应，以阐明构象应变和机理二分法。生成的烯丙基过氧化氢的各种后续反应将在还原剂、氧化剂、催化剂和亲核剂的存在下进行研究，以获得含氧平台分子的广泛化学空间。空气/氧气的连续光氧化为生物质化学品的价化提供了很大的未开发潜力。我们将通过对腰果壳废料中的腰果酚混合物进行的技术、分析和机理综合研究来证明这一概念。液体、气体和光这三个不同的“相”之间的反应通常会受到低分散(混合、光衰减)的影响。因此，我们将继续努力设计和建造新的模块化光反应器，用于停留时间在几分钟范围内的氧气/空气光氧化反应。

This project deals with the development of new substrate classes, reaction conditions, microreactor setups, and follow-up reactions of photooxygenation processes with singlet oxygen. We wish to study the effects of conformational control on the reactivity and selectivity of cyclohexene derivatives in Schenck-ene oxidations. A combined synthetic, theoretical, and operational effort will introduce new anellated cyclohexenes that engage in highly selective dioxygenation under mild conditions. Mechanistic studies will be devoted to substituent effects in bicyclic alkenes and cycloalkenylarenes to elucidate conformational strain and mechanistic dichotomies. Various follow-up reactions of the resultant allylic hydroperoxides will be studied in the presence of reductants, oxidants, catalysts, and nucleophiles to access a wide chemical space of oxygenated platform molecules. Continuous photo-oxidations with air/oxygen offer largely untapped potential for the valorization of biomass chemicals. We will demonstrate this concept in a combined technical, analytical, and mechanistic study with cardanol mixtures from cashew nutshell waste. Reactions between the three distinct "phases" liquid, gas, and light generally suffer from low dispersion (mixing, light attenuation). We will therefore continue our ongoing efforts to design and construct new modular photoreactors for applications to photooxygenations with oxygen/air with residence times in the few min range.