98446-71-0Relevant academic research and scientific papers
THE EFFECT OF ARYL SUBSTITUENTS ON ARYLCARBENE REACTIVITY
Tomioka, Hideo,Tabayashi, Kazuo,Ozaki, Yasuji,Izawa, Yasuji
, p. 1435 - 1440 (2007/10/02)
Substituted (p-MeO, p-Me, H, p-Cl, p-Br, m-Br, m-MeO, 3,4-Cl2, p-CO2Me, m-CN and p-CN) monophenylcarbenes are generated in a binary mixture of substrates (methanol, cis-4-methyl-2-pentene and cyclohexane) and the relative rate of O - H insertion into methanol to stereospecific cyclopropanation of the olefin to C - H insertion into cyclohexane are calculated from the ratios of products and substrates.It is found (i) that the reactivities of the substrates decrease in the order of methanol, olefin and cyclohexane and (ii) that electron-donating substituents generally lead to reaction with the more reactive substrates while the reaction with the less reactive substrates is favoured in the case of electron-withdrawing substituents.These results are interpreted in terms of the change in the electrophilicity of the singlet arylcarbene by the substituents rather than the change in the singlet-triplet equilibrium.
MODIFICATION OF SINGLET CARBENE REACTIVITIES BY SOLVENT
Tomoika, H.,Ozaki, Y.,Izawa, Y
, p. 4987 - 4994 (2007/10/02)
The solvent effect on the reactivity of singlet carbenes has been investigated.Competition reactions between pairs of alcohols for arylcarbenes in various solvents indicates that the O-H insertion selectivity is influenced only by 1,4-dioxane.Thus, phenylcarbene is some 33 times more reactive toward methanol relative to t-butyl alcohol in 90 molpercent dioxane than without solvent.Similar competition reactions between alcohol and olefin indicate that the O-H insertion-addition selectivities of arylcarbenes are considerably altered by dioxane.These results are interpreted as indicating that dioxane stabilizes singlet carbenes by complexing with its ione pairs of electrons.
