化学
分子内力
废止
催化作用
烯烃
钯
药物化学
立体中心
功能群
组合化学
立体化学
对映选择合成
有机化学
聚合物
作者
Tomohiko Fujii,Simone Gallarati,Clémence Corminbœuf,Qian Wang,Jieping Zhu
摘要
Benzocyclobutenes (BCBs) are highly valuable compounds in organic synthesis, medicinal chemistry, and materials science. However, catalytic modular synthesis of functionalized BCBs from easily accessible starting materials remains limited. We report herein an efficient synthesis of diversely functionalized BCBs by a Pd(II)-catalyzed formal [2+2] annulation between arylboronic acids and alkenes in the presence of N-fluorobenzenesulfonimide (NFSI). An intermolecular carbopalladation followed by palladium oxidation, intramolecular C(sp2)-H activation by a transient C(sp3)-Pd(IV) species, and selective carbon-carbon (C-C) bond-forming reductive elimination from a high-valent five-membered palladacycle is proposed to account for the reaction outcome. Kinetically competent oxidation of alkylPd(II) to alkylPd(IV) species is important to avoid the formation of a Heck adduct. The reaction forges two C-C bonds of the cyclobutene core and is compatible with a wide range of functional groups. No chelating bidentate directing group in the alkene part is needed for this transformation.
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