20071-09-4Relevant articles and documents
Fichteman,Orchin
, p. 1281 (1968)
Kauffmann
, p. 2681,2689 (1979)
Effect of Reaction Media on Photosensitized [2+2]-Cycloaddition of Cinnamates
Abramov, Alex,Reiser, Oliver,Díaz Díaz, David
, p. 649 - 656 (2020/05/25)
The outcome of photosensitized [2+2]-cycloaddition reactions of various cinnamates has been compared in different reaction media, including homogeneous organic solutions under inert conditions, degassed water, and aerated physical gels. The reactions were performed under LED blue light (λmax=455 nm) irradiation and [Ir{dF(CF3)ppy}2(dtb-bpy)]PF6 (1.0 mol%) as photocatalyst. The processes were optimized taking into consideration solvent, gelator, and substrate. Comparative kinetics analyses, as well as the effect of the reaction media on the diastereoselectivity of the process, were evaluated during this investigation. In a number of cases, carrying out the reaction in a less polar solvent, like toluene or highly polar solvent, like water had a tremendous impact on the diastereoselectivity of the process, pointing towards an effect on the stabilization of the putative diradical intermediate in this medium. Moreover, while for reactions run in homogeneous solution oxygen needs to be excluded, no erosion in yield is observed when the photoadditions were run in aerated gel media.
Visible light-induced highly selective transformation of olefin to ketone by 2,4,6-triphenylpyrylium cation encapsulated within zeolite Y
Shiraishi, Yasuhiro,Saito, Naoya,Hirai, Takayuki
, p. 773 - 775 (2008/02/03)
2,4,6-Triphenylpyrylium cation encapsulated within zeolite Y promotes highly selective transformation of olefins to ketones with molecular oxygen, under visible light (λ > 400 nm) irradiation at room temperature. The Royal Society of Chemistry 2006.
Thermal Ring-Splitting Reactions of Diarylcyclobutanes: Significance of Steric Effects on Orbital Interactions in Transition States and Biradical Intermediates
Yasuda, Masahide,Yoshida, Kouhei,Shima, Kensuke,Pac, Chyongjin,Yanagida, Shozo
, p. 1943 - 1950 (2007/10/02)
Regiochemistry and rectivities in the thermal ring-splitting reactions of diarylcyclobutanes (1-5) have been studied and shown to depend on the stable conformations and rotational mobilities of the aryl substituents.The reactions of 1 and 2 result in a regiospecific symmetric cleavage to give indene or styrene along with significant isomerization of 2 to 3.In the cases of 3-5 both the symmetric and unsymmetric cleavages competitively occur with decreasing symmetric-to-unsymmetric ratios with an increase in methyl substitution.The olefin products from 4 are mixtures of cis- and trans-2-butene, cis- and trans-β-methylstyrene, and trans-stilbene.Thermochemical analyses combined with product analyses indicate that the symetric cleavage of 1 and the unsymmetric cleavage of 3 proceed with a concerted mechanism, whereas 1,4-biradicals are involved in the other reactions.Structure-reactivity relationships of the present reactions are discussed in terms of mixing of the ?* character in a bonding MO by specific ?-?* interactions, depending on the conformational situations of the aryl groups and in terms of the steric effects which destabilize 1,4-biradicals as well as transition states of the biradical fragmentation to the olefins.