13399-33-2Relevant academic research and scientific papers
Contra-Thermodynamic Positional Isomerization of Olefins
Zhao, Kuo,Knowles, Robert R.
supporting information, p. 137 - 144 (2022/01/19)
A light-driven method for the contra-thermodynamic positional isomerization of olefins is described. In this work, stepwise PCET activation of a more substituted and more thermodynamically stable olefin substrate is mediated by an excited-state oxidant an
Stereospecific Iron-Catalyzed Carbon (sp2)-Carbon (sp2) Cross-Coupling of Aryllithium with Vinyl Halides
Chen, Peng,Peng, Xiao-Shui,Wang, Zhi-Yong,Wong, Henry N. C.
supporting information, p. 4385 - 4390 (2021/06/27)
We present herein an efficient synthetic protocol involving iron-catalyzed cross-coupling of organolithium compounds with vinyl halides as key coupling partners. More than 30 examples were obtained with moderate to good yields and high stereoselectivities. The practicality of this method is evidenced by a gram-scale synthesis. In addition, a preliminary mechanistic investigation was also performed.
Extending the Substrate Scope in the Hydrogenation of Unfunctionalized Tetrasubstituted Olefins with Ir-P Stereogenic Aminophosphine-Oxazoline Catalysts
Biosca, Maria,Salomó, Ernest,De La Cruz-Sánchez, Pol,Riera, Antoni,Verdaguer, Xavier,Pàmies, Oscar,Diéguez, Montserrat
supporting information, p. 807 - 811 (2019/01/26)
Air-stable and readily available Ir-catalyst precursors modified with MaxPHOX-type ligands have been successfully applied in the challenging asymmetric hydrogenation of tetrasubstituted olefins under mild reaction conditions. Gratifyingly, these catalyst precursors are able to efficiently hydrogenate not only a range of indene derivatives (ee's up to 96%) but also 1,2-dihydronapthalene derivatives and acyclic olefins (ee's up to 99%), which both constitute the most challenging substrates for this transformation.
Cyclopentene Annulations of Alkene Radical Cations with Vinyl Diazo Species Using Photocatalysis
Sarabia, Francisco J.,Li, Qiankun,Ferreira, Eric M.
supporting information, p. 11015 - 11019 (2018/07/30)
A direct (3+2) cycloaddition between alkenes and vinyl diazo reagents using either Cr or Ru photocatalysis is described. The intermediacy of a radical cation species enables a nucleophilic interception by vinyl diazo compounds, a departure from their trad
Direct catalytic cross-coupling of alkenyllithium compounds
Hornillos, Valentn,Giannerini, Massimo,Vila, Carlos,Faans-Mastral, Martn,Feringa, Ben L.
, p. 1394 - 1398 (2015/02/19)
A catalytic method for the direct cross-coupling of alkenyllithium reagents with aryl and alkenyl halides is described. The use of a catalyst comprising Pd2(dba)3/XPhos allows for the stereoselective preparation of a wide variety of substituted alkenes in high yields under mild conditions. In addition (1-ethoxyvinyl)lithium can be efficiently converted into substituted vinyl ethers which, after hydrolysis, give readily access to the corresponding methyl ketones in a one pot procedure.
Enantioselective synthesis of cis-1,2-disubstituted cyclopentanes and cyclohexanes by Suzuki-Miyaura cross-coupling and iridium-catalyzed asymmetric hydrogenation
Schumacher, Andreas,Schrems, Marcus G.,Pfaltz, Andreas
, p. 13502 - 13509 (2012/01/05)
A series of 1,2-disubstituted cyclohexene derivatives was prepared through Suzuki-Miyaura cross-coupling of 2-bromo-1-cyclohexenecarbaldehyde or 2-carbomethoxy-1-cyclohexen-1-yl triflate with arylboronates. These tetra-substituted cyclic alkenes were subjected to Ir-catalyzed asymmetric hydrogenation. In this way cis-1-methoxymethyl-2-arylcyclohexanes were obtained in high yield with excellent enantio- and diastereoselectivities (up to >99%ee, >99%cis) by using phosphinomethyloxazolines as ligands. Asymmetric hydrogenation of analogous cyclopentene derivatives, prepared by Suzuki-Miyaura cross-coupling, proved to be more difficult and proceeded with lower enantioselectivities of up to 88%ee. The synthetic potential of this cross-coupling/asymmetric-hydrogenation strategy was demonstrated by an enantioselective route to chiral hexahydrofluorenones. Alkene interest: Starting from arylboronates, a variety of cyclic, tetra-substituted olefins was prepared by Suzuki-Miyaura cross-coupling (see scheme). Subsequent Ir-catalyzed asymmetric hydrogenation with phosphanylmethyloxazoline ligand complexes led to cis-disubstituted cycloalkane derivatives in high yield and excellent enantio- and distereoselectivities. Copyright
Looking for a paradigm for the reactivity of phenonium ions
Protti, Stefano,Dondi, Daniele,Mella, Mariella,Fagnoni, Maurizio,Albini, Angelo
experimental part, p. 3229 - 3237 (2011/07/08)
The addition of a photogenerated phenyl cation to an alkene offers an entry, under mild conditions, to the phenethyl cation/phenonium ion system in organic solvents. Taking advantage of this, a product study has been carried out in parallel with a computational characterization of the intermediates. Thus, 4-methoxy- and 4-dimethyaminophenyl cations have been photogenerated from the corresponding chlorobenzenes in the presence of mono- to tetrasubstituted olefins in polar or protic media. The chemistry that occurs has been correlated with the degree of anchimeric assistance offered by the phenyl group, as predicted by calculations. Two limiting situations arise, the first one when starting from mono- or 1,2-disubstituted alkenes. In these cases, calculations evidence a large stabilization of the intermediate (phenonium character), particularly with electron-donating substituents on the aromatic ring, and the main products in acetonitrile are phenethyl chlorides. Variation of the ion-stabilizing solvent such as trifluoroethanol (TFE) leads to alkyl and hydride migration before chloride addition. In contrast, with less electron-rich aromatics and highly substituted alkenes the stabilization of the intermediate is modest and the typical reaction is deprotonation to yield an allylbenzene or, in TFE, the formation of a phenethyl ether. In between these two extremes, there are intermediate cases, more easily directed by a change in the conditions. These generalizations and the mildness of the method help to assess the synthetic potential of this reaction. Copyright
Synthesis of polysubstituted alkenes by Heck vinylation or Suzuki cross-coupling reactions in the presence of a tetraphosphane-palladium catalyst
Berthiol, Florian,Doucet, Henri,Santelli, Maurice
, p. 1091 - 1096 (2007/10/03)
Through the use of [PdCl(C3H5)]2/cis,cis,cis-1,2,3, 4-tetrakis[(diphenylphosphanyl)methyl]cyclopentane as a catalyst, a range of vinyl bromides undergo Suzuki cross-couplings with arylboronic acids in good yields. Furthermore, the catalyst can be used at low loadings, even for reactions of sterically hindered substrates. Mediated by this catalyst, stilbene and 1,1-diphenylethylene undergo Heck reactions with aryl halides to give triarylethylene derivatives. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Number and Structure of Solvolysis Intermediates. Part 1. A Comparison of Nucleophilic Reactions on in situ Generated Carbocations with Solvolysis Reactions for 2,2-Dimethyl-1-(p-methoxyphenyl)propyl Cation
Kinoshita,, Tomomi,Yokoi, Takakazu,Takeuchi, Ken'ichi,Okamoto, Kunio
, p. 101 - 105 (2007/10/02)
2,2-Dimethyl-1-(p-methoxyphenyl)propyl cation has been generated by treatment of the corresponding chloride with AgSbF6 in SO2-CH2Cl2 (20percent CD2Cl2) at -98 deg C and its 13C NMR spectrum observed.The reactions of the generated carbocation with methanol or phenol give products with a rearranged carbon atom skeleton and non-rearranged products with complete racemization, as expected for a typical carbocation reaction, whereas the solvolysis of the corresponding p-nitrobenzoate in phenol affords exclusively the non-rearranged products with partial retention of configuration.Such distinctions between generated carbocation reactions and the solvolysis reactions indicate that no dissociated (free) carbocation intermediate intervenes even in this solvolysis system, i.e., it is one of a few systems which have been hitherto confirmed to proceed via multiple intermediate stages.
Substituent Effects upon Efficiency of Excited-State Acetophenones Produced on Thermolysis of 3,4-Diaryl-3,4-dimethyl-1,2-dioxetanes
Richardson, William H.,Stiggal-Estberg, Diana L.,Chen, Zhangping,Baker, John C.,Burns, David M.,Sherman, David G.
, p. 3143 - 3150 (2007/10/02)
The effects of meta and para substituents upon the triplet (αT) and singlet (αS) efficiencies in the thermolysis of 3,4-diaryl-3,4-dimethyl-1,2-dioxetanes 3, 3-aryl-3,4,4-trimethyl-1,2-dioxetanes 4, and 3-aryl-3-(bromomethyl)-4,4-dimethyl-1,2-dioxetanes 5 are reported.Triplet efficiencies for series 3 dioxetanes, where the two proketone moieties are identical, are sensitive to aryl substituent changes.Attempted correlation of log αT with Hammett-type substituents constants failed, and the best correlation of log αT was with the lowest triplet energy of the acetophenones T) = (0.77+/-0.19)ET1(ArCOCH3)-55.05+/-14.00, r=0.834, Sy*x=+/-0.336>.This type of correlation was previously observed with 3-aryl-3-methyl- and 3-aryl-3-methyl-3,3-(2,2'-biphenyldiyl)-1,2-dioxetanes, where the slopes (S values) are 0.38+/-0.14 and 0.52+/-0.08, respectively.In these two dioxetane series, the triplet energies of the companion proketones (formaldehyde and fluorenone) to ArCOCH3 are approximately equal to and less than ET1(ArCOCH3).For the 4 and 5 series dioxetanes, there was no change in triplet efficiency with various aryl substituents, where the average αT values are 29.1+/-2.4percent for 4 and 28.1+/- 0.7percent for 5.For these two dioxetane series, the triplet energy of the companion proketone (acetone) is higher than ET1(ArCOCH3).With regard to triplet efficiencies, all of these dioxetane series fall into two categories: (i) where the companion proketones possess triplet energies approximately equal to or less than ET1(ArCOCH3) and where αT is dependent upon substituent changes in the ArCOCH3 moiety; (ii) where the companion proketone possesses a triplet energy higher than ET1(ArCOCH3) and αT is independent of substitution changes in the ArCOCH3 moiety.An exciplex or encounter complex process is proposed to explain the apparent communication between the two proketone moieties in category i dioxetanes.Activation parameters for series 3-5 were typical of most other tetrasubstituted dioxetanes.The ρ values for ?+ correlations of series 3 and 4 plus 5 dioxetanes are -0.285 +/- 0.033 and -0.20 +/- 0.05, respectively, which is consistent with a 1,4-dioxy biradical decomposition process.
