54849-75-1Relevant academic research and scientific papers
Unraveling innate substrate control in site-selective palladium-catalyzed C-H heterocycle functionalization
Choi, Hwanho,Min, Minsik,Peng, Qian,Kang, Dahye,Paton, Robert S.,Hong, Sungwoo
, p. 3900 - 3909 (2016)
Understanding the regioselectivity of C-H activation in the absence of directing groups is an important step towards the design of site-selective C-H functionalizations. The Pd(ii)-catalyzed direct arylation of chromones and enaminones provides an intriguing example where a simple substitution leads to a divergence in substrate-controlled site-selectivity. We describe computational and experimental studies which reveal this results from a switch in mechanism and therefore the selectivity-determining step. We present computational results and experimentally measured kinetic isotope effects and labelling studies consistent with this proposal. The C-H activation of these substrates proceeds via a CMD mechanism, which favors more electron rich positions and therefore displays a pronounced kinetic selectivity for the C3-position. However, C2-selective carbopalladation is also a competitive pathway for chromones so that the overall regiochemical outcome depends on which substrate undergoes activation first. Our studies provide insight into the site-selectivity based on the favorability of two competing CMD and carbopalladation processes of the substrates undergoing coupling. This model can be utilized to predict the regioselectivity of coumarins which are proficient substrates for carbopalladation. Furthermore, our model is able to account for the opposite selectivities observed for enaminone and chromone, and explains how a less reactive coupling partner leads to a switch in selectivity.
Palladium-catalyzed oxidative arylation of chromones via a double C-H activation: An expedient approach to flavones
Kim, Ko Hoon,Lee, Hyun Seung,Kim, Se Hee,Kim, Jae Nyoung
experimental part, p. 2761 - 2764 (2012/07/14)
A palladium-catalyzed oxidative arylation of chromones was examined. A regioselective 2-arylation of chromone was carried out via a double C-H activation process. The procedure provided an expedient approach for the preparation of flavone derivatives.
Semi-empirical and vibrational studies of flavone and some deuterated analogues
Vrielynck, L.,Cornard, J. P.,Merlin, J. C.,Lautie, M. F.
, p. 2177 - 2188 (2007/10/02)
The infrared solid state, Raman solid state and tetrachloride solution spectra of flavone have been obtained.Assignments of most of the vibrational data have been performed by comparison between the spectra of flavone and three isotopic species, deuterated on the A, B and C rings, respectively.The vibrational frequencies for all the investigated compounds have been calculated from the conformational analysis of flavone using the semi-empirical AM1 method and compared with experimental values.The correlation is more or less satisfactory; however, for some vibrational modes, the calculated isotopic shifts agree better with experiment than do the frequencies themselves.Specific vibrational modes which retain a benzene ring mono-substituted and ortho-distributed character have been recognized in the spectra, according to literature data, isotopic frequency shifts and graphic representation of the atomic displacements.
