- Access to Trisubstituted Fluoroalkenes by Ruthenium-Catalyzed Cross-Metathesis
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Although the olefin metathesis reaction is a well-known and powerful strategy to get alkenes, this reaction remained highly challenging with fluororalkenes, especially the Cross-Metathesis (CM) process. Our thought was to find an easy accessible, convenient, reactive and post-functionalizable source of fluoroalkene, that we found as the methyl 2-fluoroacrylate. We reported herein the efficient ruthenium-catalyzed CM reaction of various terminal and internal alkenes with methyl 2-fluoroacrylate giving access, for the first time, to trisubstituted fluoroalkenes stereoselectively. Unprecedent TON for CM involving fluoroalkene, up to 175, have been obtained and the reaction proved to be tolerant and effective with a large range of olefin partners giving fair to high yields in metathesis products. (Figure presented.).
- Nouaille, Augustin,Pannecoucke, Xavier,Poisson, Thomas,Couve-Bonnaire, Samuel
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supporting information
p. 2140 - 2147
(2021/03/06)
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- Controllable Isomerization of Alkenes by Dual Visible-Light-Cobalt Catalysis
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We report herein that thermodynamic and kinetic isomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction further. Transformation of exocyclic alkenes into the corresponding endocyclic products could be efficiently realized by using 4CzIPN and Co(acac)2 in the absence of any additional ligands. Spectroscopic and spectroelectrochemical investigations indicate CoI being involved in the generation of a Co hydride, which subsequently adds to alkenes initiating the isomerization.
- Meng, Qing-Yuan,Schirmer, Tobias E.,Katou, Kousuke,K?nig, Burkhard
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supporting information
p. 5723 - 5728
(2019/04/03)
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- 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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supporting information
p. 16520 - 16524
(2018/11/23)
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- Phosphorus Coordination Chemistry in Catalysis: Air Stable P(III)-Dications as Lewis Acid Catalysts for the Allylation of C-F Bonds
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Modification of C-F bonds with main-group catalysts has typically employed electron-deficient Lewis superacids in high oxidation states, and the challenges of preparing and handling such species have prevented broader adoption of metal-free reduction protocols. Here, we show that a hemilabile ligand coordinated to an easily accessed P(III) center imparts air stability without sacrificing the ability to activate C-F bonds. Catalytic C-C coupling of benzyl fluorides with allylsilanes was achieved using a P(III) complex under benchtop conditions. This application of coordination chemistry principles to main-group Lewis acids reveals a new strategy for controlling catalysis.
- Chitnis, Saurabh S.,Lafortune, James H. W.,Cummings, Haley,Liu, Liu Leo,Andrews, Ryan,Stephan, Douglas W.
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supporting information
p. 4540 - 4544
(2019/01/08)
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- Palladium-Catalyzed Electrochemical Allylic Alkylation between Alkyl and Allylic Halides in Aqueous Solution
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A new route for the direct cross-coupling of alkyl and allylic halides using electrochemical technique has been developed in aqueous media under air. Catalyzed by Pd(OAc)2, the Zn-mediated allylic alkylations proceed smoothly between a full range of alkyl halides (primary, secondary, and tertiary) and substituted allylic halides. Protection-deprotection of acidic hydrogen in the substrates is avoided.
- Lai, Yin-Long,Huang, Jing-Mei
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supporting information
p. 2022 - 2025
(2017/04/28)
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- Monocarboxylation and intramolecular coupling of butenylated arenes via palladium-catalyzed C-H activation process
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A novel and practical reaction for the direct intramolecular oxidative coupling of butenylated arenes is reported. With the catalysis of Pd(OAc)2, reactions of various butenylated arenes and carboxylic acids with Selectfluor reagent in CH3CN solution afforded the corresponding monocarboxylation/cyclization products in good yields under mild conditions. This research demonstrated an economic method with the synthesis of 2-tetralyl carboxylic esters, a valuable class of bioactive compounds.
- Liu, Rui,Lu, Ze-Hai,Hu, Xiao-Hui,Li, Jun-Li,Yang, Xian-Jin
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supporting information
p. 1489 - 1492
(2015/03/30)
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- Wacker-type oxidation and dehydrogenation of terminal olefins using molecular oxygen as the sole oxidant without adding ligand
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An efficient and economical palladium-catalyzed oxidation system has been identified. The oxidation system, characterized by not adding ligand and using molecular oxygen as the sole oxidant, can realize the Tsuji-Wacker oxidation of terminal olefins and especially styrenes to methyl ketones; in addition, this system can achieve tandem Wacker oxidation-dehydrogenation of terminal olefins to α,β-unsaturated ketones.
- Wang, Yu-Fei,Gao, Ya-Ru,Mao, Shuai,Zhang, Yan-Lei,Guo, Dong-Dong,Yan, Zhao-Lei,Guo, Shi-Huan,Wang, Yong-Qiang
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supporting information
p. 1610 - 1613
(2014/04/17)
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- Chemo-, regio-, and stereoselective iron-catalysed hydroboration of alkenes and alkynes
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The highly chemo-, regio-, and stereoselective synthesis of alkyl- and vinyl boronic esters with good functional group tolerance has been developed using in situ activation of a bench-stable iron(ii) pre-catalyst and pinacolborane (16 examples, 45-95% yield, TOF up to 30000 mol h-1). The first iron-catalysed alkene hydrogermylation is also reported.
- Greenhalgh, Mark D.,Thomas, Stephen P.
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supporting information
p. 11230 - 11232
(2013/11/19)
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- Picosecond radical kinetics. Rate constants for ring openings of 2-aryl-substituted cyclopropylcarbinyl radicals
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The kinetics of ring openings of a series of eight (trans-2-arylcyclopropyl)methyl radicals (1) were studied by indirect kinetic methods using Barton's PTOC esters as radical precursors and reaction with PhSeH as the competition reaction. The substituents were CF3, F, Me, and OMe located on both the para and meta positions of the aromatic ring. Syntheses of the radical precursors and the products of the radical reactions are described. Kinetics were determined between -43 and 25°C in four cases (CF3 and OMe substituents) and at 0 and 25°C in the other four cases. The rate constants at 25°C ranged from 1.0 x 1011 s-1 (p-CH3) to 4.1 x 1011 s-1 (p-CF3). The relatively large acceleration of the p-CF3 group, ca. 2.5 times as fast as the parent system with Ar = Ph, correlates well with Adam's ΔD substituent parameters but not with other radical substituent parameters. These calibrated radical rearrangements provide a new set of ultrafast reactions that can be applied in mechanistic probe studies.
- Newcomb,Choi,Toy
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p. 1123 - 1135
(2007/10/03)
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- Structure of ω-Arylalkyl Radicals: A 13C CIDNP Investigation
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Thermolysis of a series of ω-arylalkanoyl m-chlorobenzoyl (and acetyl) peroxides at ca. 100 deg C in cyclohexanone and in hexachloroacetone was studied by using 13C chemically induced dynamic nuclear polarization.Analysis of the observed 13C polarizations indicate that all the three radicals (β-arylethyl, γ-arylpropyl and δ-arylbutyl) have open-chain structures with no evidence for aryl participation resulting in spirocycloalkylcyclohexadienyl radicals.
- Olah, George A.,Krishnamurthy, V. V.,Singh, Brij P.,Iyer, Pradeep S.
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p. 955 - 963
(2007/10/02)
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- COMPLEXES OF TRANSITION METALS IN THE CHEMISTRY OF CONJUGATED SYSTEMS. III. REACTION OF DIENE HYDROCARBONS WITH ORGANOMAGNESIUM COMPOUNDS IN THE PRESENCE OF SALTS AND COMPLEXES OF TRANSITION METALS
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The effect of the structure of the reagents and the nature of the catalyst on the direction and selectivity in the reaction of 1,3-dienes and their derivatives with aromatic Grignard reagents was investigated.It was shown that in the presence of salts and complexes of iron(III) 1,3-alkadienes R1CH=C(R2)C(R3)=CH2 react with arylmagnesium halides to form trans-(E)-1-aryl-1,3-alkadienes, whereas the sterically hindered (R2, R3=CH3) cyclic 1,3-alkadienes and also 1,2-alkadienes give mainly adducts (1:1).Catalysis by the phosphine complexes of nickel(II) leads to the formation of telomeric (2:1) (E)-1-aryl-2,7- and (E,E)-1-aryl-2,6-alkadienes.The results demonstrate the determining role of the stereochemical conditions for the coordination of the diene in the course of the reaction and also the significant contribution from the processes of one-electron reduction of the catalyst.
- Zubritskii, L. M.,Romashchenkova, N. D.,Petrov, A. A.
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p. 2157 - 2167
(2007/10/02)
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