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Light-enabled metal-free pinacol coupling by hydrazine

Efficient carbon–carbon bond formation is of great importance in modern organic synthetic chemistry. The pinacol coupling discovered over a century ago is still one of the most efficient coupling reactions to build the C–C bond in one step. However, traditional pinacol coupling often requires over-s...

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Detalles Bibliográficos
Autores principales: Qiu, Zihang, Pham, Hanh D. M., Li, Jianbin, Li, Chen-Chen, Castillo-Pazos, Durbis J., Khaliullin, Rustam Z., Li, Chao-Jun
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Royal Society of Chemistry 2019
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7066673/
https://www.ncbi.nlm.nih.gov/pubmed/32190250
http://dx.doi.org/10.1039/c9sc03737c
Descripción
Sumario:Efficient carbon–carbon bond formation is of great importance in modern organic synthetic chemistry. The pinacol coupling discovered over a century ago is still one of the most efficient coupling reactions to build the C–C bond in one step. However, traditional pinacol coupling often requires over-stoichiometric amounts of active metals as reductants, causing long-lasting metal waste issues and sustainability concerns. A great scientific challenge is to design a metal-free approach to the pinacol coupling reaction. Herein, we describe a light-driven pinacol coupling protocol without use of any metals, but with N(2)H(4), used as a clean non-metallic hydrogen-atom-transfer (HAT) reductant. In this transformation, only traceless non-toxic N(2) and H(2) gases were produced as by-products with a relatively broad aromatic ketone scope and good functional group tolerance. A combined experimental and computational investigation of the mechanism suggests that this novel pinacol coupling reaction proceeds via a HAT process between photo-excited ketone and N(2)H(4), instead of the common single-electron-transfer (SET) process for metal reductants.