124070-55-9Relevant academic research and scientific papers
Dynamic ?-Bonding of Imidazolyl Substituent in a Formally 16-Electron Cp Ru(2-P, N)+ Catalyst Allows Dramatic Rate Increases in (E)-Selective Monoisomerization of Alkenes
Paulson, Erik R.,Moore, Curtis E.,Rheingold, Arnold L.,Pullman, David P.,Sindewald, Ryan W.,Cooksy, Andrew L.,Grotjahn, Douglas B.
, p. 7217 - 7231 (2019)
Alkene isomerization can be an atom-economical approach to generating a wide range of alkene intermediates for synthesis, but fully equilibrated mixtures of disubstituted internal alkenes typically contain significant amounts of the positional as well as geometric (E and Z) isomers. Most classical catalyst systems for alkene isomerization struggle to kinetically control either positional or E/Z isomerism. We report coordinatively unsaturated, formally 16-electron Cp Ru catalyst 5, which facilitates simultaneous regio- A nd stereoselective isomerization of linear 1-alkenes to their internal analogues, providing consistent yields of (E)-2-alkenes greater than 95%. Because nitrile-free catalyst 5 is more than 400 times faster than previously published nitrile-containing analogues 2 + 2a, very reasonable 0.1-0.5 mol % loadings of 5 complete ambient-temperature reactions within 15 min to 4 h. UV-vis, NMR, and computational studies depict the imidazolyl fragment on the phosphine as a hemilabile, four-electron donor in 2-P,N coordination. For the first time, we show direct experimental evidence that the PN ligand has accepted a proton from the substrate by characterizing the intermediate Cp Ru[??3-allyl][1-P)P-N+H], which highlights the essential role of the bifunctional ligand in promoting rapid and selective alkene isomerizations. Moreover, kinetic studies and computations reveal the role of alkene binding in selectivity of unsaturated catalyst 5.
General catalyst control of the monoisomerization of 1-alkenes to trans -2-alkenes
Larsen, Casey R.,Erdogan, Gulin,Grotjahn, Douglas B.
, p. 1226 - 1229 (2014)
After searching for the proper catalyst, the dual challenges of controlling the position of the double bond, and cis/trans-selectivity in isomerization of terminal alkenes to their 2-isomers are finally met in a general sense by mixtures of (C5Me5)Ru complexes 1 and 3 featuring a bifunctional phosphine. Typically, catalyst loadings of 1 mol % of 1 and 3 can be employed for the production of (E)-2-alkenes at 40-70 C. Catalyst comprising 1 and 3 avoids more than any other known example the thermodynamic equilibration of alkene isomers, as the trans-2-alkenes of both nonfunctionalized and functionalized alkenes are generated.
Terminal alkene monoisomerization catalysts and methods
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Page/Page column 58; 59, (2017/08/07)
The invention provides novel catalysts and methods of using catalysts for controlling the position of a double bond and cis/trans-selectivity in isomerization of terminal alkenes to their 2-isomers. Catalysts such as (pentamethylcyclopentadienyl)Ru formulas 1 and 3 having a bifunctional phosphine can be used in the methods. A catalyst loading of 1 mol % of formulas 1+3 can be employed for the production of (E)-2-alkenes at 40-70° C.; lower temperatures can be used with higher catalyst loading. Acetonitrile-free catalysts can be used at lower loadings, room temperature, and in less than a day to accomplish the same results as catalysts 1+3. The novel catalyst systems minimize thermodynamic equilibration of alkene isomers, so that the trans-2-alkenes of both non-functionalized and functionalized alkenes can be generated.
ARYLOXYACETYLINDOLES AND ANALOGS AS ANTIBIOTIC TOLERANCE INHIBITORS
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, (2016/08/10)
The disclosure provides compounds and pharmaceutical compositions of aryloxyacetylindoles compounds and analogs useful for treating chronic and acute bacterial infections. Certain of the compounds are compounds of general Formula (I) (I) or a pharmaceutically acceptable salt or prodrug thereof. Certain compounds of this disclosure are MvfR inhibitors. MvfR inhibitors reduce the formation of antibiotic tolerant bacterial strains and are useful for treating Gram-negative bacterial infections and reducing the virulence of Pseudomonas aeruginosa. Methods of treating bacterial infections in a subject, including Pseudomonas aeruginosa infections, are also provided by the disclosure.
Synthetic studies on the nhatrangins: Stereoselective access to an advanced aldehyde intermediate
Raffier, Ludovic,Piva, Olivier
, p. 1124 - 1131 (2013/03/28)
Two different strategies have been considered to achieve the first total synthesis of nhatrangins A and B. The first approach based on a cross metathesis (CM) reaction was unsuccessful. The second, which combined a highly stereoselective alkylation, a diastereoselective aldolization, and finally an esterification, furnished an advanced aldehyde intermediate bearing the three contiguous stereogenic centres and the expected side-chain. Two strategies have been considered for the stereoselective synthesis of nhatrangins A and B. A sequence involving diastereoselective alkylation and aldolization employing ephedrine derivatives as chiral auxiliaries was the most efficient approach to deliver a key aldehyde framework. Copyright
One-pot multicomponent coupling methods for the synthesis of diastereo- and enantioenriched (Z)-trisubstituted allylic alcohols
Kerrigan, Michael H.,Jeon, Sang-Jin,Chen, Young K.,Salvi, Luca,Carroll, Patrick J.,Walsh, Patrick J.
supporting information; experimental part, p. 8434 - 8445 (2009/10/23)
(Z)-Trisubstituted allylic alcohols are widespread structural motifs in natural products and biologically active compounds but are difficult to directly prepare. Introduced herein is a general one-pot multicomponent coupling method for the synthesis of (Z)-α,α,β-trisubstituted allylic alcohols. (Z)-Trisubstituted vinylzinc reagents are formed in situ by initial hydroboration of 1-bromo-1-alkynes. Addition of dialkylzinc reagents induces a 1,2-metalate rearrangement that is followed by a boron-to-zinc transmetalation. The resulting vinylzinc reagents addto a variety of prochiral aldehydes to produce racemic (Z)-trisubstitut ed allylic alcohols. When enantioenriched aldehyde substrates are employed, (Z)-trisubstituted allylic alcohols are isolated with high dr (>20:1in many cases). For example, vinylation of enantioenriched benzyl-prote cted α- and β-hydroxy propanal derivatives furnished the expected anti-Felkin addition products via chelation control. Surprisingly, silyl-protected α-hydroxy aldehydes also afford anti-Felkin addition products. A protocol for the catalytic asymmetric addition of (Z)-trisubstituted vinylzinc reagents to prochiral aldehydes with a (-)-MIB-based catalyst has also been developed. Several additives were investigatedas inhibitors of the Lewis acidic alkylzinc halide byproducts, which pr omote the background reaction to form the racemate. R-Ethyl and R-cyclohexyl (Z)-trisubstituted allylic alcohols can now be synthesized with excellent levels of enantioselectivity in the presence of diamine inhibitors.
