13657-49-3Relevant academic research and scientific papers
Expanding the Family of Hoveyda-Grubbs Catalysts Containing Unsymmetrical NHC Ligands
Paradiso, Veronica,Bertolasi, Valerio,Costabile, Chiara,Caruso, Tonino,D?browski, Micha?,Grela, Karol,Grisi, Fabia
, p. 3692 - 3708 (2017)
A series of Hoveyda-Grubbs second-generation catalysts containing N-alkyl/N′-aryl N-heterocyclic carbene (NHC) ligands were synthesized and investigated in representative olefin metathesis reactions. Steric perturbations of unsymmetrical NHCs were achieved through modulation of the hindrance of alkyl (neopentyl, neophyl, cyclohexyl) and aryl (2-isopropylphenyl, mesityl) substituents at the nitrogen atoms in combination with different backbone configurations (syn and anti). The NHC substitution patterns strongly influence the stability and reactivity of the corresponding complexes. In general, complexes bearing an anti NHC backbone are more stable and more active than their corresponding syn isomers. In both the series, the presence of bulky, highly branched N-alkyl groups tends to give reduced catalytic differences between syn and anti isomers, whereas the nature of the N′-aryl substituent (2-isopropylphenyl or mesityl) gives rise to different activity and/or selectivity. Of note, an N′-mesityl catalyst with anti backbone was found to be highly competent in the ethenolysis of ethyl oleate, achieving up to 90% selectivity for the formation of terminal olefins.
Mixed isobutylphobane/n-heterocyclic carbene ruthenium- Indenylidene complexes: Synthesis and catalytic evaluation in olefin metathesis reactions
Sauvage, Xavier,Zaragoza, Guillermo,Demonceau, Albert,Delaude, Lionel
, p. 1934 - 1948 (2010)
Two new second generation ruthenium(II) dichloride-indenylidene complexes [RuCl2(9- isobutylphosphabicyclo [3.3.1]nonane) (NHC)(3-phen- yl-1-indenylidene)], where NHC=1,3-bis(2,4,6-trimethylphenyl) imidazolin-2-ylidene (SIMes) or its unsaturated imidazol-2-ylidene analogue (IMes), were isolated in high yields upon heating a tetrahydrofuran (THF) solution of the diphosphane complex [RuCl2(isobutylphobane) 2(3-phenyl-1-indenylidene)]with a two-fold excess of the corresponding imidazol- (in)ium-2-carboxylate zwitterions. Both products were characterized by 1H, 13C, and 31P NMR spectroscopy, and the molecular structure of [RuCl2(isobutylphobane) (SIMes)(3-phenyl-1-indenylidene)]was determined by X-ray diffraction analysis. A close inspection of the packing structure revealed the presence of different types of intra- and intermolecular interactions that enhanced the global stability of the crystals, while low temperature NMR experiments showed the existence of two distinct rotational isomers due to the unsymmetrical nature of the phobane ligand. The catalytic activity of both compounds was assessed in olefin metathesis using benchmark ring-opening metathesis polymerization, ring-closing metathesis (RCM), and cross-metathesis reactions, and compared with those of related first and second generation ruthenium-benzylidene and indenylidene catalyst precursors. Kinetic studies confirmed the high thermal stability of the mixed isobutylphobane/ N-heterocyclic carbene complexes, which suffered from a slow initiation efficiency compared to other catalytic systems based on the tricyclohexylphosphane ligand. However, the remarkable robustness of [RuCl2(isobutylphobane) (SIMes)(3-phenyl-1- indenylidene)]was beneficial for performing the RCM of diethyl 2,2-bis(2-methylallyl)malonate. Monitoring the formation of the ruthenium-methylidene active species [RuCl 2(isobutylphobane)- (SIMes) (=CH2)]derived from this precursor further demonstrated its ability to sustain long reaction times and high temperatures required to carry out the RCM of tetrasubstituted olefins.
Enantioselective Synthesis of Functionalized Arenes by Nickel-Catalyzed Site-Selective Hydroarylation of 1,3-Dienes with Aryl Boronates
Marcum, Justin S.,Meek, Simon J.,Taylor, Tiffany R.
supporting information, p. 14070 - 14075 (2020/06/10)
A catalytic method for the site-selective and enantioselective synthesis of functionalized arenes by the intermolecular hydroarylation of terminal and internal 1,3-dienes with aryl pinacolato boronates is reported. The reactions are promoted by 5.0 mol %
Selective α,δ-hydrocarboxylation of conjugated dienes utilizing CO2and electrosynthesis
Buckley, Benjamin R.,Elmorsy, Saad S.,Malkov, Andrei V.,Mashaly, Mohammad A.,Said, Samy B.,Sheta, Ahmed M.
, p. 9109 - 9114 (2020/09/17)
To date the majority of diene carboxylation processes afford the α,δ-dicarboxylated product, the selective mono-carboxylation of dienes is a significant challenge and the major product reported under transition metal catalysis arises from carboxylation at the α-carbon. Herein we report a new electrosynthetic approach, that does not rely on a sacrificial electrode, the reported method allows unprecedented direct access to carboxylic acids derived from dienes at the δ-position. In addition, the α,δ-dicarboxylic acid or the α,δ-reduced alkene can be easily accessed by simple modification of the reaction conditions. This journal is
Preparation method of phenylacetaldehyde
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Paragraph 0055-0064; 0077-0080, (2020/04/17)
The invention discloses a preparation method of phenylacetaldehyde. The method comprises the following steps: taking 1, 4-diphenyl-2-butyne as a raw material, performing Lindelar catalytic hydrogenation reaction to obtain an intermediate 1, 4-diphenyl-2-butene, and performing ozonization and catalytic reduction reaction on the intermediate to obtain phenylacetaldehyde. According to the method, simple raw materials are adopted, through hydrogenation and ozonization conversion, the reaction process is environmentally friendly, the product yield is high, few byproducts are produced, and extremelyhigh atom economy is achieved.
Controllable, Sequential, and Stereoselective C-H Allylic Alkylation of Alkenes
Qin, Ling,Sharique, Mohammed,Tambar, Uttam K.
, p. 17305 - 17313 (2019/11/03)
The direct conversion of C-H bonds into new C-C bonds represents a powerful approach to generate complex molecules from simple starting materials. However, a general and controllable method for the sequential conversion of a methyl group into a fully substituted carbon center remains a challenge. We report a new method for the selective and sequential replacement of three C-H bonds at the allylic position of propylene and other simple terminal alkenes with different carbon groups derived from Grignard reagents. A copper catalyst and electron-rich biaryl phosphine ligand facilitate the formation of allylic alkylation products in high branch selectivity. We also present conditions for the generation of enantioenriched allylic alkylation products in the presence of catalytic copper and a chiral phosphine ligand. With this approach, diverse and complex products with substituted carbon centers can be generated from simple and abundant feedstock chemicals.
Loss and Reformation of Ruthenium Alkylidene: Connecting Olefin Metathesis, Catalyst Deactivation, Regeneration, and Isomerization
Engel, Julien,Smit, Wietse,Foscato, Marco,Occhipinti, Giovanni,T?rnroos, Karl W.,Jensen, Vidar R.
supporting information, p. 16609 - 16619 (2017/11/28)
Ruthenium-based olefin metathesis catalysts are used in laboratory-scale organic synthesis across chemistry, largely thanks to their ease of handling and functional group tolerance. In spite of this robustness, these catalysts readily decompose, via little-understood pathways, to species that promote double-bond migration (isomerization) in both the 1-alkene reagents and the internal-alkene products. We have studied, using density functional theory (DFT), the reactivity of the Hoveyda-Grubbs second-generation catalyst 2 with allylbenzene, and discovered a facile new decomposition pathway. In this pathway, the alkylidene ligand is lost, via ring expansion of the metallacyclobutane intermediate, leading to the spin-triplet 12-electron complex (SIMes)RuCl2 (3R21, SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene). DFT calculations predict 3R21 to be a very active alkene isomerization initiator, either operating as a catalyst itself, via a η3-allyl mechanism, or, after spin inversion to give R21 and formation of a cyclometalated Ru-hydride complex, via a hydride mechanism. The calculations also suggest that the alkylidene-free ruthenium complexes may regenerate alkylidene via dinuclear ruthenium activation of alkene. The predicted capacity to initiate isomerization is confirmed in catalytic tests using p-cymene-stabilized R21 (5), which promotes isomerization in particular under conditions favoring dissociation of p-cymene and disfavoring formation of aggregates of 5. The same qualitative trends in the relative metathesis and isomerization selectivities are observed in identical tests of 2, indicating that 5 and 2 share the same catalytic cycles for both metathesis and isomerization, consistent with the calculated reaction network covering metathesis, alkylidene loss, isomerization, and alkylidene regeneration.
Stability and activity of cis-dichloro ruthenium olefin metathesis precatalysts bearing chelating sulfur alkylidenes
Tzur, Eyal,Ivry, Elisa,Diesendruck, Charles E.,Vidavsky, Yuval,Goldberg, Israel,Lemcoff, N. Gabriel
supporting information, p. 24 - 28 (2014/08/18)
S-Chelated Grubbs type complexes are usually found in their stable cis-dichloro conformation. These precatalysts are usually latent and necessitate external stimuli to promote olefin metathesis reactions. Herein we report the synthesis of new S-chelated ruthenium complexes, by a simple exchange of the benzylidene to an alkylidene chelating ligand. The structure of the complexes was studied by NMR spectroscopy, single crystal X-ray diffraction and DFT calculations. The new complexes were tested in a series of olefin metathesis reactions and were found to be the first cis-dichloro ruthenium precatalysts that are active at room temperature. The observed differences in reactivity and structure between the alkylidene complexes and their benzylidene counterparts highlight the important influence aromaticity may have on the stability and activity of chelated Grubbs type complexes. The findings may also have implications to develop alternative strategies to stabilize, or destabilize, other organometallic complexes bearing relevant chelating ligands.
Unravelling the olefin cross metathesis on solid support. Factors affecting the reaction outcome
Poeylaut-Palena, Andres A.,Mata, Ernesto G.
scheme or table, p. 3947 - 3956 (2010/09/17)
Olefin cross metathesis on solid support under a variety of conditions is described. A comprehensive analysis considering diverse factors governing the reaction outcome gives a series of patterns for the application of this useful methodology in organic synthesis. If the intrasite reaction is not possible, homodimerization of the soluble olefin is crucial. When the homodimer is less reactive than its monomer, reaction outcome depends on the homodimerization rate, which, in turn, depends on the precatalyst used and the reaction conditions. If the site-site interaction is a feasible process, the cross metathesis product is obtained exclusively when the newly-formed double bond is resilient to further metathetic events. Taking into account these considerations, we have demonstrated that excellent results in terms of cross metathesis coupling can be obtained under the optimized conditions, and that microwave irradiation is also an interesting alternative for the development of a practical and energy-efficient cross metathesis on solid support.
