- Palladium-Catalyzed Defluorinative Alkylation of gem-Difluorocyclopropanes: Switching Regioselectivity via Simple Hydrazones
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Conventional approaches for Pd-catalyzed ring-opening cross-couplings of gem-difluorocyclopropanes with nucleophiles predominantly deliver the β-fluoroalkene scaffolds (linear selectivity). Herein, we report a cooperative strategy that can completely switch the reaction selectivity to give the alkylated α-fluoroalkene skeletons (branched selectivity). The unique reactivity of hydrazones that enables analogous inner-sphere 3,3′-reductive elimination driven by denitrogenation, as well as the assistance of steric-embedded N-heterocyclic carbene ligand, are the key to switch the regioselectivity. A wide range of hydrazones derived from naturally abundant aryl and alkyl aldehydes are well applicable, and various gem-difluorocyclopropanes, including modified pharmaceutical and biological molecules, can be efficiently functionalized with high value alkylated α-fluorinated alkene motifs under mild conditions.
- Lv, Leiyang,Li, Chao-Jun
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supporting information
p. 13098 - 13104
(2021/05/03)
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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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- Palladium-Catalyzed Formal Hydroalkylation of Aryl-Substituted Alkynes with Hydrazones
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We have developed an unprecedented Pd-catalyzed formal hydroalkylation of alkynes with hydrazones, which are generated in situ from naturally abundant aldehydes, as both alkylation reagents and hydrogen donors. The hydroalkylation proceeds with high regio- and stereoselectivity to form (Z)-alkenes, which are more difficult to generate compared to (E)-alkenes. The reaction is compatible with a wide range of functional groups, including hydroxy, ester, ketone, nitrile, boronic ester, amine, and halide groups. Furthermore, late-stage modifications of natural products and pharmaceutical derivatives exemplify its unique chemoselectivity, regioselectivity, and synthetic applicability. Mechanistic studies indicate the possible involvement of Pd-hydride intermediates.
- Yu, Lin,Lv, Leiyang,Qiu, Zihang,Chen, Zhangpei,Tan, Ze,Liang, Yu-Feng,Li, Chao-Jun
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supporting information
p. 14009 - 14013
(2020/06/10)
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- Nickel-catalyzed alkyl-alkyl cross-coupling reactions of non-activated secondary alkyl bromides with aldehydes as alkyl carbanion equivalents
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A novel nickel-catalyzed alkyl-alkyl cross coupling of non-activated secondary alkyl bromides with aldehydes via hydrazone intermediates has been developed. Aldehydes as alkyl carbanion equivalents replace traditional organometallic reagents. This coupling occurs on the carbon of the hydrazone rather than the nitrogen. In addition, non-activated primary and tertiary alkyl bromides also undergo the cross-coupling reaction to form new C(sp3)-C(sp3) bonds in moderate yields.
- Zhu, Chenghao,Zhang, Junliang
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supporting information
p. 2793 - 2796
(2019/03/06)
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- Insecticidal Triazines and Pyrimidines
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The present invention describes novel triazines, their related pyrimidines and their use in controlling insects. This invention also includes new synthetic procedures, intermediates for preparing the compounds, pesticide compositions containing the compou
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Page/Page column 11-12
(2012/02/03)
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- INSECTICIDAL (1,3,5)-TRIAZINYL PHENYL HYDRAZONES
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(1,3,5)-Triazinyl phenyl hydrazones are effective at controlling insects.
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Page/Page column 7-8
(2009/04/24)
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