AbstractThe direct benzylation of electrophilic alkenes with alkylbenzenes has been achieved by decatungstate photocatalysis in a high ionic strength medium (5:1 acetonitrile/water mixed solvents, 0.5 M lithium perchlorate). The reaction has been extended to ring‐substituted (Cl, F, CN) toluenes and further alkylbenzenes. Intramolecular selectivity (p‐cymene, 4‐methylanisole) and deuteration effects support the atom transfer character of the process that, however, requires a sufficient stabilization of the intermediate polar exciplex to occur. The reactivity of the decatungstate anion is compared with that of aromatic ketones, the benchmark of photochemical hydrogen/electron transfer processes.magnified image
Arylacetic acids were used as sources of benzyl radicals under tetrabutylammonium decatungstatephotocatalyzed conditions for the benzylation of electron-poor olefins. The reaction proceeds smoothly in a mixed aqueous medium (MeCN/H2O 2/1) in the presence of NaHCO3, NaClO4, and an electron transfer agent (biphenyl). The reaction tolerates a wide variety of functional groups on the aromatic ring (whether
在四丁基铵去癸酸盐光催化条件下,丙烯酸被用作苄基的来源,用于贫电子烯烃的苄基化。在NaHCO 3,NaClO 4和电子转移剂(联苯)的存在下,反应在混合水性介质(MeCN / H 2 O 2/1)中平稳进行。该反应可耐受芳环上的各种官能团(无论是供电子还是吸电子),并可扩展为杂芳族类似物。烯烃具有自由基陷阱和电子受体的双重作用。本方法还可扩展至芳基丙酸(包括非甾体抗炎药布洛芬和氟比洛芬),以及扁桃酸衍生物。
Decatungstate Photocatalyzed Benzylation of Alkenes with Alkylaromatics
AbstractThe direct benzylation of electrophilic alkenes with alkylbenzenes has been achieved by decatungstate photocatalysis in a high ionic strength medium (5:1 acetonitrile/water mixed solvents, 0.5 M lithium perchlorate). The reaction has been extended to ring‐substituted (Cl, F, CN) toluenes and further alkylbenzenes. Intramolecular selectivity (p‐cymene, 4‐methylanisole) and deuteration effects support the atom transfer character of the process that, however, requires a sufficient stabilization of the intermediate polar exciplex to occur. The reactivity of the decatungstate anion is compared with that of aromatic ketones, the benchmark of photochemical hydrogen/electron transfer processes.magnified image