- Umpolung of Carbonyl Groups as Alkyl Organometallic Reagent Surrogates for Palladium-Catalyzed Allylic Alkylation
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Palladium-catalyzed allylic alkylation of nonstabilized carbon nucleophiles is difficult and remains a major challenge. Reported here is a highly chemo- and regioselective direct palladium-catalyzed C-allylation of hydrazones, generated from carbonyls, as a source of umpolung unstabilized alkyl carbanions and surrogates of alkyl organometallic reagents. Contrary to classical allylation techniques, this umpolung reaction utilizes hydrazones prepared not only from aryl aldehydes but also from alkyl aldehydes and ketones as renewable feedstocks. This strategy complements the palladium-catalyzed coupling of unstabilized nucleophiles with allylic electrophiles by providing an efficient and selective catalytic alternative to the traditional use of highly reactive alkyl organometallic reagents.
- Zhu, Dianhu,Lv, Leiyang,Li, Chen-Chen,Ung, Sosthene,Gao, Jian,Li, Chao-Jun
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- Switch in Selectivity for Formal Hydroalkylation of 1,3-Dienes and Enynes with Simple Hydrazones
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Controlling reaction selectivity is a permanent pursuit for chemists. Regioselective catalysis, which exploits and/or overcomes innate steric and electronic bias to deliver diverse regio-enriched products from the same starting materials, represents a powerful tool for divergent synthesis. Recently, the 1,2-Markovnikov hydroalkylation of 1,3-dienes with simple hydrazones was reported to generate branched allylic compounds when a nickel catalyst was used. As part of the effort, shown here is that a complete switch of Markovnikov to anti-Markovnikov addition is obtained by changing to a ruthenium catalyst, thus providing direct and efficient access to homoallylic products exclusively. Isotopic substitution experiments indicate that no reversible hydro-metallation across the metal-π-allyl system occurred under ruthenium catalysis. Moreover, this protocol is applicable to the regiospecific hydroalkylation of the distal C=C bond of 1,3-enynes.
- Li, Chao-Jun,Lv, Leiyang,Qiu, Zihang,Yu, Lin
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supporting information
p. 6466 - 6472
(2020/03/13)
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- Synthesis and biological activity of some 2-imidazolinylhydrazone derivatives
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A series of N-(imidazolidin-2-ylidene)hydrazones and N-(4,5-dihydro-1H- imidazol-2-yl)-N-methylhydrazones were prepared and examined for α1-, α2-adrenergic and imidazoline I 1, I2 receptors binding affinities as well as cytotoxic activity against human tumor cell lines. Among the compounds tested, 2-naphthaldehyde N-(imidazolidin-2-ylidene)hydrazone (3e) exhibited a significant affinity for both α2-adrenergic and imidazoline I1 receptors (Ki = 94.3 nM and IC50 = 51.7 nM, respectively). Moreover, pyridine-2-carboxaldehyde N-(imidazolidin-2-ylidene) hydrazone (3l) showed the highest binding affinity to α1- adrenoceptors (Ki = 24.6 nM), while quinoline-2-carboxaldehyde N-(imidazolidin-2-ylidene)hydrazone (3m) displayed the highest I2 affinity with a Ki value of 26.7 nM and a high selectivity with respect to α2-adrenergic and imidazoline I1 receptors (Ki = 22470.0 nM and IC50 = 6145.0 nM, respectively). None of the tested N-(4,5-dihydro-1H-imidazol-2-yl)-N- methylhydrazones 4p-u displayed cytotoxic activity.
- Kornicka, Anita,Hudson, Alan L.,Bednarski, Patrick J.
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experimental part
p. 523 - 534
(2010/02/27)
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- A novel synthetic approach to dichlorostyrenes
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We found that N-unsubstituted hydrazones of aromatic aldehydes can be easily converted to the corresponding 1,1-dichlorostyrenes in the reaction with carbon tetrachloride using copper (I) chloride as catalyst. Factors affecting the route of the reaction and yields of the products were investigated. A proposed mechanism for the reaction is discussed. (C) 2000 Published by Elsevier Science Ltd.
- Shastin,Korotchenko,Nenajdenko,Balenkova
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p. 6557 - 6563
(2007/10/03)
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