- Light-enabled metal-free pinacol coupling by hydrazine
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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 N2H4, used as a clean non-metallic hydrogen-atom-transfer (HAT) reductant. In this transformation, only traceless non-toxic N2 and H2 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 N2H4, instead of the common single-electron-transfer (SET) process for metal reductants.
- Qiu, Zihang,Pham, Hanh D. M.,Li, Jianbin,Li, Chen-Chen,Castillo-Pazos, Durbis J.,Khaliullin, Rustam Z.,Li, Chao-Jun
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p. 10937 - 10943
(2019/12/23)
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- A novel lanthanum metal-assisted reaction of diaryl ketones and electrophiles
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A novel and efficient lanthanum metal-assisted carbon-carbon bond formation of diaryl ketones and various electrophiles, such as carbonyl compounds, esters, nitriles, and epoxides, has been developed. When diaryl ketones were allowed to react with dialkyl ketones in the presence of lanthanum metal and a catalytic amount of iodine, the cross pinacol coupling reaction proceeded to give the corresponding unsymmetrical 1,2-diols in moderate to good yields. α-Hydroxy ketones were prepared by the lanthanum metal-assisted reaction of diaryl ketones with esters or nitriles, followed by hydrolysis with aq HCl. It is interesting to note that for the epoxides, the coupling reaction proceeded via the Meinwald rearrangement of epoxides to give the corresponding 1,2-diols.
- Umeda, Rui,Ninomiya, Masashi,Nishino, Toshiaki,Kishida, Makoto,Toiya, Shunsuke,Saito, Tomoki,Nishiyama, Yutaka,Sonoda, Noboru
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p. 1287 - 1291
(2015/03/05)
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- A one-pot cross-pinacol coupling/rearrangement procedure
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A new catalytic retro-pinacol/cross-pinacol reaction, followed by subsequent rearrangement or deoxygenation of the intermediately formed vicinal diols, is described. This operationally simple one-pot protocol allows isolation of geminal α,α-diphenyl ketones or 1,1-diphenyl alkenes with high yields and selectivities. Copyright
- Scheffler, Ulf,Mahrwald, Rainer
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p. 1970 - 1975,6
(2012/12/12)
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- Retropinacol/cross-pinacol coupling reactions - A catalytic access to 1,2-unsymmetrical diols
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A new concept to access unsymmetrical 1,2-diols with high yields is reported. This new methodology is based on a retropinacol/cross-pinacol coupling process. This transformation is characterized by its operational simplicity and very mild reaction condi tions.
- Scheffler, Ulf,Stoesser, Reinhard,Mahrwald, Rainer
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supporting information
p. 2648 - 2652,5
(2012/12/12)
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