A series of neutral coinage‐metal boryl complexes featuring a side‐on [B=C]− containing ligand have been isolated and characterised. The compounds are isoelectronic with alkene complexes, which are crucial intermediates in catalysis. Both the strength of binding and the propensity for deviation toward η1 coordination are more favourable for Au over Ag and Cu.
Abstract
A series of linear late transition metal (M=Cu, Ag, Au and Zn) complexes featuring a side‐on [B=C]− containing ligand have been isolated and characterised. The [B=C]− moiety is isoelectronic with the C=C system of an alkene. Comparison across the series shows that in the solid‐state, deviation between the η2 and η1 coordination mode occurs. A related zinc complex containing two [B=C]− ligands was prepared as a further point of comparison for the η1 coordination mode. The bonding in these new complexes has been interrogated by computational techniques (QTAIM, NBO, ETS‐NOCV) and rationalised in terms of the Dewar–Chatt–Duncanson model. The combined structural and computational data provide unique insight into catalytically relevant linear d10 complexes of Cu, Ag and Au. Slippage is proposed to play a key role in catalytic reactions of alkenes through disruption and polarisation of the π‐system. Through the preparation and analysis of a consistent series of group 11 complexes, we show that variation of the metal can impact the coordination mode and hence substrate activation.
https://ift.tt/3uc5vhY
A high‐throughput method was developed using a colorimetric indicator displacement assay (IDA) to quantify the alkene stereochemistry present within mixtures to an accuracy of 2–3 %. Within a series of 96‐well plates, alkenes were dihydroxylated and the resulting diols were subjected to an IDA with an indicator and a boronic acid to determine the amount of threo and/or erythro vicinal diols present.
Abstract
A colorimetric indicator displacement assay (IDA) amenable to high‐throughput experimentation was developed to determine the percentage of cis and trans alkenes. Using 96‐well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis or trans alkenes, depending upon their syn‐ or anti‐addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis and trans alkenes. Blind mixtures of cis and trans alkenes were made, resulting in an average error of ±2 % in the percentage of cis or trans alkenes, and implementing E2 and Wittig reactions gave errors of ±3 %. Furthermore, we developed variants of the IDA for which the color may be tuned to optimize the response for the human eye.
https://ift.tt/3liButi
A strategy is presented for nickel‐ catalyzed asymmetric reductive carbo‐carboxylation of alkenes with CO2. A variety of aryl (pseudo)halides react to produce oxindole‐3‐acetic acid derivatives bearing a C3‐quaternary stereocenter. Notably, synthesis of a range of bioactive pyrroloindolines was achieved.
Abstract
Reductive carboxylation of organo (pseudo)halides with CO2 is a powerful method to provide carboxylic acids quickly. Notably, the catalytic reductive carbo‐carboxylation of unsaturated hydrocarbons via CO2 fixation is a highly challenging but desirable approach for structurally diverse carboxylic acids. There are only a few reports and no examples of alkenes via transition metal catalysis. We report the first asymmetric reductive carbo‐carboxylation of alkenes with CO2 via nickel catalysis. A variety of aryl (pseudo)halides, such as aryl bromides, aryl triflates and inert aryl chlorides of particular note, undergo the reaction smoothly to give important oxindole‐3‐acetic acid derivatives bearing a C3‐quaternary stereocenter. This transformation features mild reaction conditions, wide substrate scope, facile scalability, good to excellent chemo‐, regio‐ and enantioselectivities. The method highlights the formal synthesis of (−)‐Esermethole, (−)‐Physostigmine and (−)‐Physovenine, and the total synthesis of (−)‐Debromoflustramide B, (−)‐Debromoflustramine B and (+)‐Coixspirolactam A; thereby, opening an avenue for the total synthesis of chiral natural products with CO2.
https://ift.tt/3rJAKPv
https://preview.redd.it/0t8f2wg96ey61.png?width=2556&format=png&auto=webp&s=72b4c103f3a0bc4fd896efdc27f36b72e4e14ed7
And the 1 ended up on the ene not the yne according to the below youtube video
https://preview.redd.it/dzybqpqe6ey61.png?width=824&format=png&auto=webp&s=0516661ca3a39aab0b286236dc09d06d178a2567
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c03454
Hui-Yi Yang, Ya-Hong Yao, Ming Chen, Zhi-Hui Ren, and Zheng-Hui Guan
https://ift.tt/3ocrt2b
Hi! I'm halfway done through my Chemistry 1 book and I'm just curious why the suffix -ylene is sometimes used instead of -ene for alkyls with a double bond. I looked it up and found that -ylene is actually obsolete but I wonder why it is still used in textbooks. I appreciate any clarifications! Thanks :)
I know that there is probably some reasoning that makes sense for why E is the trans alkene and Z is the cis alkene, but it still really bothers me. Like I mean cmon, the letter Z is in the shape of a trans alkene! Why is it not the trans one? E is also the shape of a cis alkene! They're reversed! Someone definitely missed out an opportunity here.
A three‐component 1,2‐aminoarylation of vinyl ethers, enamides, ene‐carbamates and vinyl thioethers by synergistic photoredox and nickel catalysis is reported. 2,2,2‐Trifluoroethoxy carbonyl protected α‐amino‐oxy acids are used as amidyl radical precursors. anti ‐Markovnikov addition of the amidyl radical to the alkene and subsequent Ni‐mediated radical/transition metal cross over lead to the corresponding 1,2‐aminoarylation product. The radical cascade, that can be conducted under practical and mild conditions, features high functional group tolerance and broad substrate scope. Stereoselective 1,2‐aminoarylation is achieved using a L‐(+)‐lactic acid derived vinyl ether as the substrate, offering a novel route for the preparation of protected enantiopure α‐arylated β‐amino alcohols. In addition, 1,2‐aminoacylation of vinyl ethers is achieved by using an acyl succinimide as the electrophile for the Ni‐mediated radical coupling.
https://ift.tt/2QGffSA
The C–C bond formation reaction represents a fundamental and important transformation in synthetic chemistry, and exploring new types of C–C bond formation reactions is recognized as appealing, yet challenging. Herein, we disclose the first example of rhodium‐catalyzed dealkenylative arylation of alkenes with arylboronic compounds, thereby providing an unconventional access to bi(hetero)aryls with excellent chemo‐selectivity. In this method, C(aryl)–C(alkenyl) and C(alkenyl)–C(alkenyl) bonds in various alkenes and 1,3‐dienes can be cleaved via a hydrometalation and followed by beta‐carbon elimination pathway for Suzuki‐Miyaura reaction. Furthermore, a series of novel organic fluorescent molecules with excellent photophysical properties has been efficiently constructed with this protocol.
https://ift.tt/3xTlDr2
Robust [NiFe] hydrogenase 1 (Hyd1) from Escherichia coli is shown to have non‐native, H2‐dependent activity for FMN and FAD reduction. It is a promising recycling system for FMNH2 or FADH2 supply to flavoenzymes for chemical synthesis when coupled with an Old Yellow Enzyme ene‐reductase.
Abstract
A new activity for the [NiFe] uptake hydrogenase 1 of Escherichia coli (Hyd1) is presented. Direct reduction of biological flavin cofactors FMN and FAD is achieved using H2 as a simple, completely atom‐economical reductant. The robust nature of Hyd1 is exploited for flavin reduction across a broad range of temperatures (25–70 °C) and extended reaction times. The utility of this system as a simple, easy to implement FMNH2 or FADH2 regenerating system is then demonstrated by supplying reduced flavin to Old Yellow Enzyme “ene‐reductases” to support asymmetric alkene reductions with up to 100 % conversion. Hyd1 turnover frequencies up to 20.4 min−1 and total turnover numbers up to 20 200 were recorded during flavin recycling.
https://ift.tt/38KXibI
Control over dynamic motion at the molecular level and stimuli‐responsiveness are important issues for making nano‐motors, nano‐actuators or nano‐sensors. Elucidation of dynamics of molecular rotational motion is an essential part and still challenging area of research. In this report, demonstration of reversible diastereomeric interconversion of a molecular rotor composed of overcrowded butterfly‐shape alkene ( FDF ) is given. Its inherent dual rotatory motion (two rotors, one stator) with interconversion between two diastereomers, chiral trans ‐ FDF and meso cis ‐ FDF forms, has been examined in detail upon varying temperatures and solvents. The free energy profile of 180 ° revolution of one rotor part has a bimodal shape with unevenly positioned maxima (i.e. transition states). FDF in aromatic solvents adopts preferentially meso cis ‐conformation, while in non‐aromatic solvents a chiral trans ‐conformation is more abundant. Additionally, moderate correlations between the trans ‐ FDF / cis ‐ FDF ratio and solvent parameters, such as refractive index, polarizability, and viscosity were found. The results presented here have implementations in several fields of organic chemistry, such as design of artificial molecular machines, asymmetric/stereoselective reactions and solvent properties scales.
https://ift.tt/3dTX3y8
A novel Pd(II)‐catalyzed enantioselective oxycarbonyl‐ation of alkenes has been established herein. The ligand with an ethyl group at the C‐6 position of Pyox plays a significant role in the intermolecular oxypalladation process, leading to high reactivity and excellent enantioselective control. Compared to the conventional methods, the reaction itself features alkenes as easily prepared starting materials, mild and operationally simple reaction conditions, and insensitivities to air and water. Moreover, this method allows for broad alkene substrate scope, excellent regio‐ and enantio‐selectivities, scalabilities and a wide array of applications, and provides a useful route for the convenient and straightforward synthesis of chiral β ‐hydroxy alkylcarboxylic acids/esters.
https://ift.tt/2R5upRz
Methyl groups are ubiquitous in biologically active molecules. Thus, new tactics to introduce this alkyl fragment into polyfunctional structures are of significant interest. With this goal in mind, a direct method for the Markovnikov hydromethylation of alkenes is reported. This method exploits the degenerate metathesis reaction between the titanium methylidene unveiled from Cp2Ti(m‐Cl)(m‐CH2)AlMe2 (Tebbe’s reagent) and unactivated alkenes. Protonolysis of the resulting titanacyclobutanes in situ effects hydromethylation in a chemo‐, regio‐, and site‐selective manner. The broad utility of this method is demonstrated across a series of mono‐ and di‐substituted alkenes containing pendant alcohols, ethers, amides, carbamates and basic amines.
https://ift.tt/2Q75X2t
Basically the title of the post. In naming alkenes, is it always necessary to designate E/Z? What do you do if you have 2 of the same group on one of your double bonded carbons?
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c01022
Kun Liu and Armido Studer
https://ift.tt/3fcf0ZK
The highly diastereoselective Fe‐catalyzed anaerobic Markovnikov‐selective hydration of alkenes using nitroarenes as oxygenation reagents is reported.
Abstract
Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama‐type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe‐catalyzed anaerobic Markovnikov‐selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov‐selectivity. The method features large functional group tolerance and is also applicable for late‐stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
https://ift.tt/3sFG9Zc
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c03077
Samuel N. Gockel, Travis L. Buchanan, and Kami L. Hull
https://ift.tt/3cUUOdk
A photoredox‐catalyzed iminoalkenylation of γ‐alkenyl O‐acyl oximes has been developed. Readily available alkenylboronic acids serve as alkenylation reagents, leading to densely functionalized pyrrolines. Both (E)‐ and (Z)‐cinnamylpyrrolines are accessible depending on the reaction solvent. Two stereocenters are established with complete diastereoselectivity and only one diastereomer is isolated. PC=photocatalyst, SET=single‐electron transfer, EnT=energy transfer.
Abstract
A photoredox‐catalyzed iminoalkenylation of γ‐alkenyl O‐acyl oximes has been developed. Readily available alkenylboronic acids serve as alkenylation reagents, leading to densely functionalized pyrrolines. Both (E)‐ and (Z)‐cinnamylpyrrolines are accessible depending on the reaction solvent. In dichloromethane, (E)‐cinnamylpyrrolines are produced through a photoredox‐mediated single‐electron‐transfer process. In tetrahydrofuran, (Z)‐cinnamylpyrrolines are generated by photocatalytic contra‐thermodynamic E‐to‐Z isomerization of (E)‐cinnamylpyrrolines though an energy‐transfer pathway. Two stereocenters are established with complete diastereoselectivity and only one diastereomer is isolated.
https://ift.tt/3rvrUFE
Hello all, I'm hydrogenating an alkene, the compound also has a primary hydroxyl group present. The alkene is hydrogenating fine but my alcohol is also being oxidized to an aldehyde. Does anyone have an suggestions to prevent this? 10%pd/c at r.t.
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c02629
Benxiang Zhang, Jiayan He, Yi Li, Tao Song, Yewen Fang, and Chaozhong Li
https://ift.tt/3u8OmVW
The photocatalytic hydroboration of alkenes and alkynes is reported. The use of newly‐designed copper photocatalysts with B 2 Pin 2 permits the formation a boryl radical, which is used for hydroboration of a large panel of alkenes and alkynes. The hydroborated products were isolated in high yields, with excellent diastereoselectivities and a high functional group tolerance under mild conditions. The hydroboration reactions were developed under continuous flow conditions to demonstrate their synthetic utility. The reaction mechanism was studied and suggested an oxidation reaction between an in situ formed borate and the Cu‐photocatalyst in its excited state for the boryl radical formation.
https://ift.tt/3diZclx
Journal of the American Chemical SocietyDOI: 10.1021/jacs.1c02747
Nicholas L. Reed, Grace A. Lutovsky, and Tehshik P. Yoon
https://ift.tt/2OUESig
The influence of the acid site density on the diffusivities of alkanes and alkenes through the 8‐ring windows of SAPO‐34 was probed using a complementary set of ab initio MD simulations and experimental techniques (PFG‐NMR and TAP pulse‐response measurements). The presence of Brønsted acid sites was found to have a clear promotional effect on alkene diffusion but it does not influence alkane diffusion.
Abstract
The diffusion of saturated and unsaturated hydrocarbons is of fundamental importance for many zeolite‐catalyzed processes. Transport of small alkenes in the confined zeolite pores can become hindered, resulting in a significant impact on the ultimate product selectivity and separation. Herein, intracrystalline light olefin/paraffin diffusion through the 8‐ring windows of zeolite SAPO‐34 is characterized by a complementary set of first‐principle molecular dynamics simulations, PFG‐NMR experiments, and pulse‐response temporal analysis of products measurements, yielding information at different length and time scales. Our results clearly show a promotional effect of the presence of Brønsted acid sites on the diffusion rate of ethene and propene, whereas transport of alkanes is found to be insensitive to the presence of acid sites. The enhanced diffusivity of unsaturated hydrocarbons is ascribed to the formation of favorable π–H interactions with acid protons, as confirmed by IR spectroscopy measurements. The acid site distribution is proven to be an important design parameter for optimizing product distributions and separations.
https://ift.tt/2NifFxu
By means of a synergistic theoretical and experimental approach, Veronique Van Speybroeck et al. show in their Research Article (DOI: 10.1002/anie.202017025) that the presence of Brønsted acid sites promotes ethene diffusion through the cages of H‐SAPO‐34, whereas ethane diffusion remains invariant for the acid site density. The interaction of ethene with the acid sites (yellow dots) facilitates the diffusion through the catalyst, leading to a shorter diffusion path (blue pathway) compared to ethane which follows a random trajectory (orange pathway.
https://ift.tt/3rds97g
Tertiary amines can be used as substrates for the highly regioselective intermolecular hydroaminoalkylation of alkenes in the presence of a cationic titanium catalyst generated in situ from tetrabenzyltitanium and Ph3C[B(C6F5)4]. While in most cases, the involved C−H bond activation reaction occurs at N‐methyl groups, N‐methylazepane and N‐methylpyrrolidine also undergo alkylation at the methylene group in position α to the nitrogen atom.
Abstract
The first cationic titanium catalyst system for the intermolecular hydroaminoalkylation of alkenes with various tertiary alkylamines is presented. Corresponding reactions which involve the addition of the α‐C−H bond of a tertiary amine across the C−C double bond of an alkene take place at temperatures close to room temperature with excellent regioselectivity to deliver the branched products exclusively. Interestingly, for selected amines, α‐C−H bond activation occurs not only at N‐methyl but also at N‐methylene groups.
https://ift.tt/3shwbwY
A series of neutral coinage‐metal boryl complexes featuring a side‐on [B=C]− containing ligand have been isolated and characterised. The compounds are isoelectronic with alkene complexes, which are crucial intermediates in catalysis. Both the strength of binding and the propensity for deviation toward η1 coordination are more favourable for Au over Ag and Cu.
Abstract
A series of linear late transition metal (M=Cu, Ag, Au and Zn) complexes featuring a side‐on [B=C]− containing ligand have been isolated and characterised. The [B=C]− moiety is isoelectronic with the C=C system of an alkene. Comparison across the series shows that in the solid‐state, deviation between the η2 and η1 coordination mode occurs. A related zinc complex containing two [B=C]− ligands was prepared as a further point of comparison for the η1 coordination mode. The bonding in these new complexes has been interrogated by computational techniques (QTAIM, NBO, ETS‐NOCV) and rationalised in terms of the Dewar–Chatt–Duncanson model. The combined structural and computational data provide unique insight into catalytically relevant linear d10 complexes of Cu, Ag and Au. Slippage is proposed to play a key role in catalytic reactions of alkenes through disruption and polarisation of the π‐system. Through the preparation and analysis of a consistent series of group 11 complexes, we show that variation of the metal can impact the coordination mode and hence substrate activation.
https://ift.tt/3uc5vhY
Reductive carboxylation of organo (pseudo)halides with CO 2 is a powerful method to provide carboxylic acids quickly. Notably, the catalytic reductive carbo‐carboxylation of unsaturated hydrocarbons via CO 2 fixation is a highly challenging but desirable approach for structurally diverse carboxylic acids. However, there are only a few reports but no examples of alkenes via transition‐metal catalysis. Herein, we report the first asymmetric reductive carbo‐carboxylation of alkenes with CO 2 via nickel catalysis. A variety of aryl (pseudo)halides, such as aryl bromides, aryl triflates and inert aryl chlorides of particular note, undergo the reaction smoothly to give important oxindole‐3‐acetic acid derivatives bearing a C3‐quaternary stereocenter. This transformation features mild reaction conditions, wide substrate scope, facile scalability, good to excellent chemo‐, regio‐ and enantio‐selectivities. Importantly, the method is highlighted by the formal synthesis of (‐)‐Esermethole, (‐)‐Physostigmine and (‐)‐Physovenine, as well as the total synthesis of (‐)‐Debromoflustramide B, (‐)‐Debromoflustramine B and (+)‐Coixspirolactam A, opening an avenue for the total synthesis of chiral natural products with CO 2 .
https://ift.tt/3rJAKPv
A colorimetric indicator displacement assay (IDA) amenable to high‐throughput experimentation was developed to determine the percentage of cis‐ and trans‐alkenes. Using 96‐well plates two steps are performed: a reaction plate for dihydroxylation of the alkenes followed by an IDA screening plate consisting of an indicator and a boronic acid. The dihydroxylation generates either erythro or threo vicinal diols from cis‐ or trans‐alkenes depending upon their syn‐ or anti‐addition mechanisms. Threo diols preferentially associate with the boronic acid due to the creation of more stable boronate esters, thus displacing the indicator to a greater extent. The generality of the protocol was demonstrated using seven sets of cis‐ and trans‐alkenes. Further, blind mixtures of cis‐ and trans‐alkenes were made resulting in an average error of ± 2% in the percentage of cis‐ or trans‐alkenes, and implementing E2 and Wittig reactions gave errors of ± 3%. Furthermore, we developed variants of the IDA that alter the color changes to optimize the response to the human eye.
https://ift.tt/3liButi
