Stable benzopyrylium tetrafluoroborates, prepared by palladium-catalyzed annulation of aryl triisopropylsilylethynyl ethers with internal alkynes followed by BF3·OEt2 treatment, exhibited solid-state luminescence upon UV irradiation.
Palladium-catalyzed Cycloaddition of Aryl Silylethynyl Ethers with Isocyanates via<i>o</i>-C–H Cleavage
作者:Yasunori Minami、Mayuko Kanda、Tamejiro Hiyama
DOI:10.1246/cl.140452
日期:2014.9.5
Palladium-catalyzed cycloaddition of alkynyl aryl ethers with isocyanates proceeds through o-C–H activation to afford 2-methylidene-2H-1,4-benzoxazin-3(4H)-one derivatives. Deuterium-labeling experiment shows that o-hydrogen is cleaved selectively and migrated to 2-methylidene moiety in the product. Various substrates are applied to this transformation to afford various substituted cycloadducts. 1,4-Bis(alkynoxy)benzenes can be used for the synthesis of multicondensed cycles to afford benzo[1,2-b:4,5-b′]bis[1,4]oxazine-3,8-dione derivatives.
Alkynyl aryl ethers react with internal alkynes through selective ortho C-H activation by a palladium(0) catalyst to give substituted 2-methylidene-2H-chromenes. The alkynoxy group acts as a directing group to promote ortho C-H functionalization. Deuterium-labeling experiments indicated that the arylpalladium hydride complex is a key intermediate via oxidative addition. Various functional groups tolerate
An intramolecular exo‐hydroarylation of 2‐aryloxy‐1,4‐disilylbut‐1‐en‐3‐ynes via ortho‐C−H bond activation under palladium(0) and acid catalysis was found to give 2,3‐bis(silylmethylidene)‐2,3‐dihydrobenzofurans. The two silyl groups present probably promoted the reaction and played a key role in stabilizing the diene moiety in the product. The products readily led to functionalized condensed cycles
Dehydrogenative Carbon–Carbon Bond Formation Using Alkynyloxy Moieties as Hydrogen‐Accepting Directing Groups
作者:Yasunori Minami、Tatsuro Kodama、Tamejiro Hiyama
DOI:10.1002/anie.201505789
日期:2015.9.28
α,ß‐unsaturated esters, or heteroarenes results in the site‐selective cleavage of two CH bonds followed by the formation of CC bonds. In all cases, the alkynyloxygroup acts as a directinggroup for the activation of an ortho CH bond and as a hydrogenacceptor, thus rendering the use of additives such as an oxidant or base unnecessary.