Redox-Neutral [4 + 2] Annulation of N-Methoxybenzamides with Alkynes Enabled by an Osmium(II)/HOAc Catalytic System
2019
Yang, Jian | Wu, Liexin | Xu, Huiying | Gao, Hui | Zhou, Zhi | Yi, Wei
By making use of a direct C–H activation strategy, an efficient osmium(II)-catalyzed redox-neutral [4 + 2] annulation of N-methoxybenzamides with alkynes has been accomplished. Computational and experimental studies revealed that such transformation leading to the synthesis of the isoquinolone core might follow an Os(II)–Os(IV)–Os(II) catalytic pathway, in which an unusual HOAc-assisted oxidative addition of osmium(II) into the N–O bond to generate the osmium(IV) species was involved as one of the key transition states. Further exploration of divergent C–H activation reaction modes enabled by the osmium(II) catalyst has also been exemplified for one-pot assembly of other either linear or cyclic products.
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