- An easy route to N,N-diarylhydrazines by Cu-catalyzed arylation of pyridine-2-carbaldehyde hydrazones with aryl halides
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A copper-catalyzed C-N coupling reaction is described for the preparation of pyridine-2-carbaldehyde N,N-diarylhydrazones by the arylation of N-mono- or -non-substituted hydrazones with aryl bromides/iodides, and the subsequent conversion of the hydrazones into N,N-diarylhydrazines by a transimination process with an aqueous solution of H2NNH2. The reaction features the use of CuI as the catalyst without the need for external ligands. This methodology provides a convenient alternative to the synthesis of structurally diverse N,N-diarylhydrazines from simple, easily accessible precursors. Copyright
- Wu, Wei,Li, Xin-Le,Fan, Xin-Heng,Yang, Lian-Ming
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p. 862 - 867
(2013/03/28)
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- Groups 5 and 6 terminal hydrazido(2-) complexes: Nβ substituent effects on ligand-to-metal charge-transfer energies and oxidation states
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Brightly colored terminal hydrazido(2-) (dme)MCl3(NNR 2) (dme = 1,2-dimethoxyethane; M = Nb, Ta; R = alkyl, aryl) or (MeCN)WCl4(NNR2) complexes have been synthesized and characterized. Perturbing the electronic environment of the β (NR 2) nitrogen affects the energy of the lowest-energy charge-transfer (CT) transition in these complexes. For group 5 complexes, increasing the energy of the Nβ lone pair decreases the ligand-to-metal CT (LMCT) energy, except for electron-rich niobium dialkylhydrazides, which pyramidalize Nβ in order to reduce the overlap between the Nb=N α π bond and the Nβ lone pair. For W complexes, increasing the energy of Nβ eventually leads to reduction from formally [WVI≡N-NR2] with a hydrazido(2-) ligand to [WIV=N=NR2] with a neutral 1,1-diazene ligand. The photophysical properties of these complexes highlight the potential redox noninnocence of hydrazido ligands, which could lead to ligand- and/or metal-based redox chemistry in early transition metal derivatives.
- Tonks, Ian A.,Durrell, Alec C.,Gray, Harry B.,Bercaw, John E.
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p. 7301 - 7304
(2012/06/16)
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