2445-83-2Relevant articles and documents
ORIENTATION EFFECTS IN THE PECHMANN REACTION SYNTHESIS OF 5,6-DIMETHYLCOUMARIN AND AN EXAMINATION OF ORTHO-PROXIMITY EFFECTS IN 13C NMR SPECTROSCOPY
Osborne, A. G.
, p. 2021 - 2025 (1981)
In the Pechmann reaction with malic acid, m-cresol and 3,4-xylenol give mixtures of alkylcoumarins containing about 10percent of the 5- and 5,6-isomers respectively. 7-Alkylcoumarins only are obtained from the reaction with ethylacetoacetate.A study of ortho-proximity effects on the 13C NMR of dimethylcoumarins is reported, and the results have been correlated with similar effects in other aromatic and heteroaromatic systems.
Cycloreversion performance of coumarin and hetero-coumarin dimers under aerobic conditions: Unexpected behavior triggered by UV-A light
Bieniek, Nikolai,Hampp, Norbert,Inacker, Sebastian
, p. 17703 - 17712 (2021/08/30)
Photochemical [2+2]-cycloadditions of coumarin-like monomers are the textbook paradigms of photo-formation and photo-cleavage reactions. The electronic conjugation length of monomers and dimers is quite different which results in almost fully separated UV/Vis absorption bands in the UV-A and UV-C. This feature enables the selective light-controlled conversion between monomeric and dimeric forms by the choice of the appropriate wavelengths. Several applications are based on this kind of reversible photo linker without absorption in the visible range. But which is the best molecule from the coumarin family for such an application? Within this study, we compared the photochemical cleavage behavior of twelve coumarin-type cyclobutane dimers. In particular, the influence of isomer structure and substitution pattern was studied. Two dimers with an unexpected high quantum yield for cyclobutane cleavage were identified. This behavior is explained through the differing ring strain of the cyclobutane moiety. Electron donating substitutions of the framework, e.g. with a methoxy function (+M-effect), leads to a decreased oxidation potential, making the dimers sensitive towards oxidative dimer splitting. This result disqualifies coumarins, e.g. attached to a polymer backbone via an ether bond, often in the 7-position, because of their instabilities and side reactions in an aerobic environment. The methylated dimers (+I-effect) show excellent stability towards this undesired side reaction as well as a high cleavage efficiency upon irradiation with 265 nm. All twelve investigated dimers are ranked for their quantum efficiency and rate constant for cleavage at 265 nm, as well as their oxygen tolerance. As the most promising derivative within our scope for applications the methylated coumarin dimer was identified.
Synthesis method of coumarin derivatives
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Paragraph 0054-0056, (2020/09/23)
The invention provides a synthesis method of coumarin derivatives. The synthesis method comprises the following steps: adding polyphosphoric acid PPA and a solvent N,N-dimethylformamide DMF, sequentially adding substituted salicylaldehyde and acetic anhydride, and carrying out a heating stirring reaction for 3-6 h under nitrogen protection; and after the reaction is finished, separating and purifying to obtain the coumarin derivative pure products. The synthesis method disclosed by the invention is disclosed for the first time, is short in reaction time, simple to operate, low in catalyst usage amount, cheap, easy to obtain and relatively good in derivative yield, not only provides a new method for synthesizing coumarin derivatives, but also provides more possibilities for large-scale production of products and improvement of production efficiency.
