Photocatalytic esterification under Mitsunobu reaction conditions mediated by flavin and visible light
作者:M. März、J. Chudoba、M. Kohout、R. Cibulka
DOI:10.1039/c6ob02770a
日期:——
The usefulness of flavin-based aerial photooxidation in esterification underMitsunobu reaction conditions was demonstrated, providing aerial dialkyl azodicarboxylate recycling/generation from the corresponding dialkyl hydrazine dicarboxylate. Simultaneously, activation of triphenylphosphine (Ph3P) by photoinduced electron transfer from flavin allows azo-reagent-free esterification. An optimized system
Flavin Catalysis Employing an N(5)-Adduct: an Application in the Aerobic Organocatalytic Mitsunobu Reaction
作者:Michal März、Martin Babor、Radek Cibulka
DOI:10.1002/ejoc.201900397
日期:2019.6.2
An N(5)‐flavin adduct was utilized in a catalytic Mitsunobureaction with triphenylphosphane (triphenylphosphine), in which flavin acts as a Mitsunobu reagent instead of dialkyl azodicarboxylate. Flavin is used in a catalytic amount after regeneration by dioxygen.
single-electron oxidation. Unexpected stereoselectivity control by the solvent was observed, allowing switching from inversion to retention of configuration during esterification of (S)- or (R)-1-phenylethanol; for example with phenylacetic acid, the ratio shifting from 10 : 90 (retention : inversion) in trifluoromethylbenzene to 99.9 : 0.1 in acetonitrile. Our method uses nitrobenzene to regenerate the flavin
Clear cut: For the title reaction, O2, the ideal oxidant, was used as the only oxidizing reagent. The dimer intermediate (see scheme) and isotopic labeling control experiments with 18O2 partially disclosed the reaction mechanism.
清晰:对于标题反应,使用理想的氧化剂O 2作为唯一的氧化剂。用18 O 2进行的二聚体中间体(参见方案)和同位素标记对照实验部分揭示了反应机理。