- Metal-Free Intermolecular Coupling of Arenes with Secondary Amides: Chemoselective Synthesis of Aromatic Ketimines and Ketones, and N-Deacylation of Secondary Amides
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The direct transformation of common secondary amides into aromatic ketimines and aromatic ketones with C-C bond formation is described. The reaction can also be used for N-deacylation of secondary amides to release amines. This method consists of in situ amide activation with triflic anhydride and intermolecular capture of the resulting highly electrophilic nitrilium intermediate with an arene. The reaction is applicable to various kinds of secondary amides (electrophiles), but only electron-rich and moderately electron-rich arenes can be used as nucleophiles. Thanks to the use of bench stable arenes instead of reactive and basic organometallics as nucleophiles, the reaction proceeded with high chemoselectivity at the secondary amido group in the presence of a series of sensitive functional groups such as aldehyde, ketone, ester, cyano, nitro, and tertiary amido groups. The reaction can be viewed as a Friedel-Crafts-type reaction using secondary amides as acylating agents or as an intermolecular version of the Bischler-Napieralski reaction.
- Huang, Pei-Qiang,Huang, Ying-Hong,Xiao, Kai-Jiong
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p. 9020 - 9027
(2016/10/17)
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- Efficient Synthesis of Diaryl Ketones by Nickel-Catalyzed Negishi Cross-Coupling of Amides by Carbon–Nitrogen Bond Cleavage at Room Temperature Accelerated by a Solvent Effect
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The first Negishi cross-coupling of amides for the synthesis of versatile diaryl ketones by selective C?N bond activation under exceedingly mild conditions is reported. The cross-coupling was accomplished with bench-stable, inexpensive precatalyst [Ni(PPh3)2Cl2] that shows high functional-group tolerance and enables the synthesis of highly functionalized diaryl ketone motifs. The coupling occurred with excellent chemoselectivity favoring the ketone (cf. biaryl) products. Notably, this process represents the mildest conditions for amide N?C bond activation accomplished to date (room temperature, 10 min). Considering the versatile role of polyfunctional biaryl ketone linchpins in modern organic synthesis, availability, and excellent functional-group tolerance of organozinc reagents, this strategy provides a new platform for amide N?C bond/organozinc cross-coupling under mild conditions.
- Shi, Shicheng,Szostak, Michal
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p. 10420 - 10424
(2016/07/21)
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- Infrared study of polysubstitution effects in benzophenones and acetophenones: contribution of inter and intracycle interaction mechanisms
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The carbonyl stretching frequencies of substituted 2-Me, 2,6-diMe, 2-MeO benzophenones and 2-Me, 2-MeO acetophenones have been measured in diluted CCl4 solutions.Two interaction mechanisms are observed.In X, Y substituted benzophenones with X on the same cycle as the ortho group and Y on the other cycle, it is shown that for X=Y, the effect of Y is greater than that of X except for very strong electron-releasing substituents.In this last case, the observed enhancement is attributed to the joint effects of intercycle interactions excercised on X and Y and of intracycle interaction on X.These results are corroborated by the study of substituted acetophenones in which only the intracycle mechanism can play a role.
- Goethals, G.,Nadio, L.,Uzan, R.
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p. 199 - 204
(2007/10/02)
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