achieved via photocatalysis. This protocol exhibits a broad scope of lignin models and excellent compatibility of functionalization reagents, constructing a series of functionalized lignin-based aromatic compounds. Highly selective formation of alkyl radical species through a proton-coupled electrontransfer and β-scission process provides the opportunity to form new C–C and C–N bonds by reaction with
Unconventional Titania Photocatalysis: Direct Deployment of Carboxylic Acids in Alkylations and Annulations
作者:David W. Manley、Roy T. McBurney、Phillip Miller、Russell F. Howe、Shona Rhydderch、John C. Walton
DOI:10.1021/ja306168h
日期:2012.8.22
Under dry, anaerobic conditions, TiO2 photocatalysis of carboxylic add precursors resulted in carbon-carbon bond-forming processes. High yields of dirners were obtained from TiO2 treatment of carboxylic acids alone: On inclusion of electron-deficient alkenes, efficient alkylations were achieved with methoxymethyl and phenoxymethyl radicals. In reactions with maleic anhydride or maleimides, phenoxyacetic acid produced chromenedione derivatives in addition to adducts. These photocatalytic reactions are simple and cheap to perform, and the TiO2 is easily removed by filtration. The anaerobic photocatalysis strategy offers a range of synthetic possibilities.
Titania-Promoted Carboxylic Acid Alkylations of Alkenes and Cascade Addition–Cyclizations
作者:David W. Manley、Roy T. McBurney、Phillip Miller、John C. Walton、Andrew Mills、Christopher O’Rourke
DOI:10.1021/jo4027929
日期:2014.2.7
electron-deficient alkenes. The efficiency of alkylation varied appreciably with substituents in the carboxylic acids. The reactions of aryloxyacetic acids with maleimides resulted in a cascade process in which a pyrrolochromene derivative accompanied the alkylated succinimide. The selectivity for one or other of these products could be tuned to some extent by employing the photoredoxcatalyst under different
使用 TiO 2 的光化学反应和羧酸在干燥厌氧条件下导致几种类型的 C-C 键形成过程与缺电子烯烃。烷基化的效率随羧酸中的取代基而显着变化。芳氧基乙酸与马来酰亚胺的反应导致了一个级联过程,其中吡咯并色烯衍生物伴随着烷基化的琥珀酰亚胺。通过在不同条件下使用光氧化还原催化剂,可以在一定程度上调整这些产品中的一种或其他产品的选择性。通过包含 2-烯基、2-芳基或 2-肟基官能团而适用于分子内闭环的芳氧基乙酸反应相当差。这些系统的反应物消耗和产物形成的概况是通过原位核磁共振监测技术获得的。对一系列不同的催化剂形式进行了效率和易用性测试。所提出的机制,涉及在 TiO2 上的空穴捕获2表面由羧酸盐随后 CO 2损失得到中间体的 EPR 光谱证据的支持。氘标记表明二氧化钛可能从表面羟基提供质子并提供电子和空穴,因此既是催化剂又是反应伙伴。