6911-81-5Relevant academic research and scientific papers
The Catalytic Asymmetric Intermolecular Prins Reaction
Diáz-Oviedo, C. David,Maji, Rajat,List, Benjamin
supporting information, p. 20598 - 20604 (2021/12/14)
Despite their significant potential, catalytic asymmetric reactions of olefins with formaldehyde are rare and metal-free approaches have not been previously disclosed. Here we describe an enantioselective intermolecular Prins reaction of styrenes and paraformaldehyde to form 1,3-dioxanes, using confined imino-imidodiphosphate (iIDP) Br?nsted acid catalysts. Isotope labeling experiments and computations suggest a concerted, highly asynchronous addition of an acid-activated formaldehyde oligomer to the olefin. The enantioenriched 1,3-dioxanes can be transformed into the corresponding optically active 1,3-diols, which are valuable synthetic building blocks.
Visible light-mediated metal-free double bond deuteration of substituted phenylalkenes
Iakovenko, Roman,Hlavá?, Jan
supporting information, p. 440 - 446 (2021/01/28)
Various bromophenylalkenes were reductively photodebrominated by using 1,3-dimethyl-2-phenyl-1H-benzo-[d]imidazoline (DMBI) and 9,10-dicyanoanthracene. With deuterated DMBI analogs (the most effective was DMBI-d11), satisfactory to excellent isotopic yields were obtained. DMBI-d11 could also be regenerated from the reaction mixtures with a recovery rate of up to 50%. The combination of the photodebromination reaction with conventional methods for bromoalkene synthesis enables sequential monodeuteration of a double bond without the necessity of a metal catalyst. This journal is
Iron(ii)-catalyzed intermolecular aziridination of alkenes employing hydroxylamine derivatives as clean nitrene sources
Berhal, Farouk,Grimaud, Laurence,Kirby, Georgina,Prestat, Guillaume,Vitale, Maxime R.
, p. 9428 - 9432 (2021/12/09)
The iron-catalyzed intermolecular aziridination of alkenes with hydroxylamine derivatives is described. Using simple iron(ii) sources and readily available ligands, the formal (2 + 1) cycloaddition process proved to be efficient on both styrenes and aliphatic alkenes, providing access to a wide range of aziridines. In these particularly sustainable reaction conditions, yields up to 89% could be obtained, with a catalyst loading which could be lowered to 5 mol% when the reaction was performed on large scale. Preliminary mechanistic studies suggest that both concerted and stepwise pathways are operating in this transformation. This journal is
Manganese-catalysed divergent silylation of alkenes
Dong, Jie,Yuan, Xiang-Ai,Yan, Zhongfei,Mu, Liying,Ma, Junyang,Zhu, Chengjian,Xie, Jin
, p. 182 - 190 (2020/12/17)
Transition-metal-catalysed, redox-neutral dehydrosilylation of alkenes is a long-standing challenge in organic synthesis, with current methods suffering from low selectivity and narrow scope. In this study, we report a general and simple method for the manganese-catalysed dehydrosilylation and hydrosilylation of alkenes, with Mn2(CO)10 as a catalyst precursor, by using a ligand-tuned metalloradical reactivity strategy. This enables versatility and controllable selectivity with a 1:1 ratio of alkenes and silanes, and the synthetic robustness and practicality of this method are demonstrated using complex alkenes and light olefins. The selectivity of the reaction has been studied using density functional theory calculations, showing the use of an iPrPNP ligand to favour dehydrosilylation, while a JackiePhos ligand favours hydrosilylation. The reaction is redox-neutral and atom-economical, exhibits a broad substrate scope and excellent functional group tolerance, and is suitable for various synthetic applications on a gram scale. [Figure not available: see fulltext.].
Synthesis and Reactivity of Organometallic Intermediates Relevant to Cobalt-Catalyzed Hydroformylation
Chirik, Paul J.,MacNeil, Connor S.,Mendelsohn, Lauren N.,Pabst, Tyler P.,Zhong, Hongyu
supporting information, p. 8912 - 8916 (2020/04/15)
Intermediates relevant to cobalt-catalyzed alkene hydroformylation have been isolated and evaluated in fundamental organometallic transformations relevant to aldehyde formation. The 18-electron (R,R)-(iPrDuPhos)Co(CO)2H has been stru
Geometric E→Z Isomerisation of Alkenyl Silanes by Selective Energy Transfer Catalysis: Stereodivergent Synthesis of Triarylethylenes via a Formal anti-Metallometallation
Fa?bender, Svenja I.,Molloy, John J.,Mück-Lichtenfeld, Christian,Gilmour, Ryan
, p. 18619 - 18626 (2019/11/16)
An efficient geometrical E→Z isomerisation of alkenyl silanes is disclosed via selective energy transfer using an inexpensive organic sensitiser. Characterised by operational simplicity, short reaction times (2 h), and broad substrate tolerance, the reaction displays high selectivity for trisubstituted systems (Z/E up to 95:5). In contrast to thermal activation, directionality results from deconjugation of the π-system in the Z-isomer due to A1,3-strain thereby inhibiting re-activation. The structural importance of the β-substituent logically prompted an investigation of mixed bis-nucleophiles (Si, Sn, B). These versatile linchpins also undergo facile isomerisation, thereby enabling a formal anti-metallometallation. Mechanistic interrogation, supported by a theoretical investigation, is disclosed together with application of the products to the stereospecific synthesis of biologically relevant target structures.
Hydrogen on Cobalt Phosphide
Delley, Murielle F.,Wu, Zishan,Mundy, M. Elizabeth,Ung, David,Cossairt, Brandi M.,Wang, Hailiang,Mayer, James M.
supporting information, p. 15390 - 15402 (2019/11/02)
Cobalt phosphide (CoP) is one of the most promising earth-abundant replacements for noble metal catalysts for the hydrogen evolution reaction (HER). Critical to HER is the binding of H atoms. While theoretical studies have computed preferred sites and energetics of hydrogen bound to transition metal phosphide surfaces, direct experimental studies are scarce. Herein, we describe measurements of stoichiometry and thermochemistry for hydrogen bound to CoP. We studied both mesoscale CoP particles, exhibiting phosphide surfaces after an acidic pretreatment, and colloidal CoP nanoparticles. Treatment with H2 introduced large amounts of reactive hydrogen to CoP, ca. 0.2 H per CoP unit, and on the order of one H per Co or P surface atom. This was quantified using alkyne hydrogenation and H-atom transfer reactions with phenoxy radicals. Reactive H atoms were even present on the as-prepared materials. On the basis of the reactivity of CoP with various molecular hydrogen donating and accepting reagents, the distribution of binding free energies for H atoms on CoP was estimated to be roughly 51-66 kcal mol-1 (δG°H 0 to -0.7 eV vs H2). Operando X-ray absorption spectroscopy gave preliminary indications about the structure of hydrogenated CoP, showing a slight lattice expansion and no significant change of the effective nuclear charge of Co under H2-flow. These results provide a new picture of catalytically active CoP, with a substantial amount of reactive H atoms. This is likely of fundamental relevance for its catalytic and electrocatalytic properties. Additionally, the approach developed here provides a roadmap to examine hydrogen on other materials.
Organoiron- And Fluoride-Catalyzed Phosphinidene Transfer to Styrenic Olefins in a Stereoselective Synthesis of Unprotected Phosphiranes
Geeson, Michael B.,Transue, Wesley J.,Cummins, Christopher C.
supporting information, p. 13336 - 13340 (2019/09/10)
Catalytic phosphiranation has been achieved, allowing preparation of trans-1-R-2-phenylphosphiranes (R = t-Bu: 1-t-Bu; i-Pr: 1-i-Pr) from the corresponding dibenzo-7-(R)-7-phospha-norbornadiene (RPA, A = C14H10, anthracene) and styre
Why is cis/trans stereoinversion with Li+(THF)4 migration across the phenyl ring of α-lithiostyrene accelerated by two ortho-methyl groups?
Knorr, Rudolf,Lattke, Ernst,Ruhdorfer, Jakob,Ferchland, Kathrin,von Roman, Ulrich
supporting information, p. 1621 - 1631 (2018/02/28)
Common wisdom might anticipate that two methyl groups placed on a molecular migration route should act as an impediment. However, the “conducted tour” migration of Li+(THF)4 across the aryl ring (“π-route”) during the cis/trans stereoinversion of α-arylvinyllithiums had been found to occur with practically equal velocities in the presence of either one or two ortho-alkyl substituents. We now report that the omission of both ortho-methyl groups retards the stereoinversion process. In order to arrive at an answer to the title question, we investigate the aggregation equilibria and microsolvation states of ortho, ortho′-unsubstituted α-lithiostyrenes by means of approved secondary NMR criteria. Beyond such necessary knowledge about the ground-state properties, we provide kinetic evidence showing that the retarded cis/trans stereoinversion of α-lithiostyrene proceeds by the pseudomonomolecular, ionic mechanism with Li+(THF)4 migration.
Additive-modulated switchable reaction pathway in the addition of alkynes with organosilanes catalyzed by supported Pd nanoparticles: Hydrosilylation: versus semihydrogenation
Duan, Yanan,Ji, Guijie,Zhang, Shaochun,Chen, Xiufang,Yang, Yong
, p. 1039 - 1050 (2018/03/05)
We herein report supported Pd nanoparticles on N,O-doped hierarchical porous carbon as a single operation catalyst-enabled additive-modulated reaction pathway for alkynes addition with organosilanes between hydrosilyation and semihydrogenation. In the case of alkynes hydrosilylation, a simple iodide ion as an additive has a promotion effect on the activity and regio- and stereoselectivity, where iodide can coordinate with Pd NPs via strong δ donation to increase the electron density of the Pd atom, resulting in an increased ability for the oxidative addition of hydrosilane as the rate-determining step to make the reaction proceed efficiently to afford vinylsilanes in high yields with excellent regio- and stereoselectivity. For the catalytic transfer semihydrogenation of alkynes, water was introduced to mix with organosilane to form a silanol together with the generation of hydrogen atoms on the Pd NPs surface or the liberation of H2 gas as a reducing agent, whereby the quantitative reduction of alkynes was achieved with exclusive selectivity to alkenes. In both cases, the catalyst could be recycled several times without a significant loss in activity or selectivity. A broad range of alkyl and aryl alkynes with various functional groups are compatible with the reaction conditions. The role the additive exerted in each reaction was extensively investigated through control experiments as well as the kinetic isotopic effect along with spectroscopic characterization. In addition, the respective mechanism operating in both reactions was proposed.
