Publications by authors named "Janis Louie"

48 Publications

Trends in the Usage of Bidentate Phosphines as Ligands in Nickel Catalysis.

Chem Rev 2020 07 3;120(13):6124-6196. Epub 2020 Jun 3.

Department of Chemistry, University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112, United States.

A critically important process in catalysis is the formation of an active catalyst from the combination of a metal precursor and a ligand, as the efficacy of this reaction governs the amount of active catalyst. This Review is a comprehensive overview of reactions catalyzed by nickel and an added bidentate phosphine, focusing on the steps transforming the combination of precatalyst and ligand into an active catalyst and the potential effects of this transformation on nickel catalysis. Reactions covered include common cross-coupling reactions, such as Suzuki, Heck, Kumada, and Negishi couplings, addition reactions, cycloadditions, C-H functionalizations, polymerizations, hydrogenations, and reductive couplings, among others. Overall, the most widely used nickel precatalyst with free bidentate phosphines is Ni(cod), which accounts for ∼50% of the reports surveyed, distantly followed by Ni(acac) and Ni(OAc), which account for ∼10% each. By compiling the reports of these reactions, we have calculated statistics of the usage and efficacy of each ligand with Ni(cod) and other nickel sources. The most common bidentate phosphines are simple, relatively inexpensive ligands, such as DPPE, DCPE, DPPP, and DPPB, along with others with more complex backbones, such as DPPF and Xantphos. The use of expensive chiral phosphines is more scattered, but the most common ligands include BINAP, Me-Duphos, Josiphos, and related analogs.
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http://dx.doi.org/10.1021/acs.chemrev.9b00682DOI Listing
July 2020

Total Synthesis of Indolizidine Alkaloids via Nickel-Catalyzed (4 + 2) Cyclization.

Org Lett 2020 02 13;22(3):924-928. Epub 2020 Jan 13.

Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-8450 , United States.

A Ni-catalyzed (4 + 2) cycloaddition of alkynes and azetidinones toward piperidinones was used as key reaction in the enantioselective synthesis of naturally occurring indolizidine alkaloids. The reaction benefits from the use of an easily accessible azetidinone as an advanced and divergent intermediate to build the indolizidine core. This methodology has been applied in the total syntheses of (+)-septicine, (+)-ipalbidine, and (+)--antofine to illustrate the applicability of the general approach.
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http://dx.doi.org/10.1021/acs.orglett.9b04479DOI Listing
February 2020

Hierarchical Self-Assembly of a Water-Soluble Organoplatinum(II) Metallacycle into Well-Defined Nanostructures.

Org Lett 2018 11 29;20(22):7020-7023. Epub 2018 Oct 29.

Department of Chemistry , University of Utah , 315 South 1400 East, Room 2020 , Salt Lake City , Utah 84112 , United States.

A water-soluble metallosupramolecular hexagon containing pendant methyl viologen (MV) and trimethylammonium units at the vertices has been synthesized via an organoplatinum(II) ← pyridyl coordination-driven self-assembly reaction. The MV units of the metallacycle were further utilized in the formation of a heteroternary complex with cucurbit[8]uril and a galactose-functionalized naphthalene derivative, yielding a metallacycle-cored carbohydrate cluster that was subsequently ordered into nanospheres and tapes, depending upon the concentration.
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http://dx.doi.org/10.1021/acs.orglett.8b02925DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6385591PMC
November 2018

Orthogonal self-assembly of an organoplatinum(II) metallacycle and cucurbit[8]uril that delivers curcumin to cancer cells.

Proc Natl Acad Sci U S A 2018 08 23;115(32):8087-8092. Epub 2018 Jul 23.

Department of Chemistry, University of Utah, Salt Lake City, UT 84112;

Curcumin (Cur) is a naturally occurring anticancer drug isolated from the plant. It is known to exhibit anticancer properties via inhibiting the STAT3 phosphorylation process. However, its poor water solubility and low bioavailability impede its clinical application. Herein, we used organoplatinum(II) ← pyridyl coordination-driven self-assembly and a cucurbit[8]uril (CB[8])-mediated heteroternary host-guest complex formation in concert to produce an effective delivery system that transports Cur into the cancer cells. Specifically, a hexagon 1, containing hydrophilic methyl viologen (MV) units and 3,4,5-Tris[2-[2-(2-methoxyethoxy)ethoxy]ethoxy]benzoyl groups alternatively at the vertices, has been synthesized and characterized by several spectroscopic techniques. The MV units of 1 underwent noncovalent complexation with CB[8] to yield a host-guest complex 4. Cur can be encapsulated in 4, via a 1:1:1 heteroternary complex formation, resulting in a water-soluble host-guest complex 5. The host-guest complex 5 exhibited 100-fold improved IC values relative to free Cur against human melanoma (C32), melanoma of rodents (B16F10), and hormone-responsive (MCF-7) and triple-negative (MDA-MB231) breast cancer cells. Moreover, strong synergisms of Cur with 1 and 4 with combinatorial indexes of <1 across all of the cell lines were observed. An induced apoptosis with fragmented DNA pattern and inhibited expression of phosphor-STAT3 supported the improved therapeutic potential of Cur in heteroternary complex 5.
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http://dx.doi.org/10.1073/pnas.1803800115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6094119PMC
August 2018

Regioselective Iron-Catalyzed [2 + 2 + 2] Cycloaddition Reaction Forming 4,6-Disubstituted 2-Aminopyridines from Terminal Alkynes and Cyanamides.

J Org Chem 2017 01 13;82(1):234-242. Epub 2016 Dec 13.

Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112, United States.

Iron complexes bound by redox-active pyridine dialdimine (PDAI) ligands catalyze the cycloaddition of two terminal alkynes and one cyanamide. The reaction is both chemo- and regioselective, as only 4,6-disubstituted 2-aminopyridine products are formed in moderate to high yields. Isolation of an iron azametallacycle (4) suggests that catalyst deactivation occurs with a large excess of cyanamide over longer reaction times. Fe-catalyzed cycloaddition allowed for a straightforward synthesis of a variety of aminopyridines, including known estrogen receptor ligands.
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http://dx.doi.org/10.1021/acs.joc.6b02374DOI Listing
January 2017

Hexaaminobenzene as a building block for a Family of 2D Coordination Polymers.

J Am Chem Soc 2017 01 21;139(1):19-22. Epub 2016 Dec 21.

Department of Chemistry and ‡Department of Physics and Astronomy, University of Utah , Salt Lake City, Utah 84112, United States.

A family of 2D coordination polymers were successfully synthesized through "bottom-up" techniques using Ni, Cu, Co, and hexaaminobenzene. Liquid-liquid and air-liquid interfacial reactions were used to realize thick (∼1-2 μm) and thin (<10 nm) stacked layers of nanosheet, respectively. Atomic-force microscopy and scanning electron microscopy both revealed the smooth and flat nature of the nanosheets. Selected area diffraction was used to elucidate the hexagonal crystal structure of the framework. Electronic devices were fabricated on thin samples of the Ni analogue and they were found to be mildly conducting and also showed back gate dependent conductance.
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http://dx.doi.org/10.1021/jacs.6b09889DOI Listing
January 2017

Synergy between Experimental and Computational Chemistry Reveals the Mechanism of Decomposition of Nickel-Ketene Complexes.

J Am Chem Soc 2016 Oct 14;138(42):14083-14091. Epub 2016 Oct 14.

Department of Chemistry, The University of Utah , 315 S 1400 E, Salt Lake City, Utah 84112, United States.

A series of (dppf)Ni(ketene) complexes were synthesized and fully characterized. In the solid state, the complexes possess η-(C,O) coordination of the ketene in an overall planar configuration. They display similar structure in solution, except in some cases, the η-(C,C) coordination mode is also detected. A combination of kinetic analysis and DFT calculations reveals the complexes undergo thermal decomposition by isomerization from η-(C,O) to η-(C,C) followed by scission of the C═C bond, which is usually rate limiting and results in an intermediate carbonyl carbene complex. Subsequent rearrangement of the carbene ligand is rate limiting for electron poor and sterically large ketenes, and results in a carbonyl alkene complex. The alkene readily dissociates, affording alkenes and (dppf)Ni(CO). Computational modeling of the decarbonylation pathway with partial phosphine dissociation reveals the barrier is reduced significantly, explaining the instability of ketene complexes with monodentate phosphines.
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http://dx.doi.org/10.1021/jacs.6b08897DOI Listing
October 2016

An in Situ Approach to Nickel-Catalyzed Cycloaddition of Alkynes and 3-Azetidinones.

J Org Chem 2015 Oct 6;80(20):9951-8. Epub 2015 Oct 6.

Department of Chemistry, University of Utah , 315 South, 1400 East, Salt Lake City, Utah 84112-0850, United States.

An efficient and convenient procedure that generates the active Ni(0) catalyst in situ from cheap, air stable Ni(II) precursors is developed for the [4 + 2]-cycloaddition of alkynes and 3-azetidinones. The reaction affords useful 3-dehydropiperidinones in comparable yields to the reported Ni(0) procedure. Additionally, the cycloaddition with 3-oxetanone afforded the 3-dehydropyranone product. Chiral 2-substituted azetidinones were also tolerated to form substituted dehydropiperidinones in high yield and enantiomeric excess.
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http://dx.doi.org/10.1021/acs.joc.5b01458DOI Listing
October 2015

Advances in nickel-catalyzed cycloaddition reactions to construct carbocycles and heterocycles.

Acc Chem Res 2015 Aug 22;48(8):2354-65. Epub 2015 Jul 22.

Department of Chemistry, University of Utah, 315 South, 1400 East, Salt Lake City, Utah 84112-0850, United States.

Transition-metal catalysis has revolutionized the field of organic synthesis by facilitating the construction of complex organic molecules in a highly efficient manner. Although these catalysts are typically based on precious metals, researchers have made great strides in discovering new base metal catalysts over the past decade. This Account describes our efforts in this area and details the development of versatile Ni complexes that catalyze a variety of cycloaddition reactions to afford interesting carbocycles and heterocycles. First, we describe our early work in investigating the efficacy of N-heterocyclic carbene (NHC) ligands in Ni-catalyzed cycloaddition reactions with carbon dioxide and isocyanate. The use of sterically hindered, electron donating NHC ligands in these reactions significantly improved the substrate scope as well as reaction conditions in the syntheses of a variety of pyrones and pyridones. The high reactivity and versatility of these unique Ni(NHC) catalytic systems allowed us to develop unprecedented Ni-catalyzed cycloadditions that were unexplored due to the inefficacy of early Ni catalysts to promote hetero-oxidative coupling steps. We describe the development and mechanistic analysis of Ni/NHC catalysts that couple diynes and nitriles to form pyridines. Kinetic studies and stoichiometric reactions confirmed a hetero-oxidative coupling pathway associated with this Ni-catalyzed cycloaddition. We then describe a series of new substrates for Ni-catalyzed cycloaddition reactions such as vinylcyclopropanes, aldehydes, ketones, tropones, 3-azetidinones, and 3-oxetanones. In reactions with vinycyclopropanes and tropones, DFT calculations reveal noteworthy mechanistic steps such as a C-C σ-bond activation and an 8π-insertion of vinylcyclopropane and tropone, respectively. Similarly, the cycloaddition of 3-azetidinones and 3-oxetanones also requires Ni-catalyzed C-C σ-bond activation to form N- and O-containing heterocycles.
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http://dx.doi.org/10.1021/acs.accounts.5b00054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6681814PMC
August 2015

Ni(NHC)]-catalyzed cycloaddition of diynes and tropone: apparent enone cycloaddition involving an 8π insertion.

J Am Chem Soc 2014 Dec 5;136(51):17844-51. Epub 2014 Dec 5.

Department of Chemistry, University of Utah , 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States.

A Ni/N-heterocyclic carbene catalyst couples diynes to the C(α)-C(β) double bond of tropone, a type of reaction that is unprecedented for metal-catalyzed cycloadditions with aromatic tropone. Many different diynes were efficiently coupled to afford [5-6-7] fused tricyclic products, while [5-7-6] fused tricyclic compounds were obtained as minor byproducts in a few cases. The reaction has broad substrate scope and tolerates a wide range of functional groups, and excellent regioselectivity is found with unsymmetrical diynes. Theoretical calculations show that the apparent enone cycloaddition occurs through a distinctive 8π insertion of tropone. The initial intramolecular oxidative cyclization of diyne produces the nickelacyclopentadiene intermediate. This intermediate undergoes an 8π insertion of tropone, and subsequent reductive elimination generates the [5-6-7] fused tricyclic product. This initial product undergoes two competing isomerizations, leading to the observed [5-6-7] and [5-7-6] fused tricyclic products.
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http://dx.doi.org/10.1021/ja5105206DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4291811PMC
December 2014

Synthesis, mechanism of formation, and catalytic activity of Xantphos nickel π-complexes.

Chem Commun (Camb) 2014 Dec 30;50(98):15577-80. Epub 2014 Oct 30.

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112, USA.

A general synthetic route to the first Xantphos nickel alkyne and alkene complexes has been discovered. Various Ni π-complexes were prepared and characterized. NMR experiments indicate benzonitrile undergoes ligand exchange with a Xantphos ligand of (Xant)2Ni, a compound that was previously believed to be unreactive. The Ni π-complexes were also shown to be catalytically competent in cross coupling and cycloaddition reactions. (Xant)2Ni is also catalytically active for these reactions when activated by a nitrile or coordinating solvent.
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http://dx.doi.org/10.1039/c4cc07590kDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4343202PMC
December 2014

Mechanistic Evaluation of the Ni(IPr)-Catalyzed Cycloaddition of Alkynes and Nitriles to Afford Pyridines: Evidence for the Formation of a Key -Ni(IPr)(RCN) Intermediate.

Organometallics 2013 Sep;32(17):4952-4960

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States.

A detailed mechanistic evaluation of the Ni(IPr)-catalyzed [2+2+2]-cycloaddition of diynes and nitriles was 2 conducted. Through kinetic analysis of these reactions, observed regioselectivities of the products, and stoichiometric reactions, Ni(IPr)-catalyzed cycloadditions of diynes and nitriles appear to proceed by a heterooxidative coupling mechanism, contrary to other common cycloaddition catalysts. Reaction profiles demonstrated strong dependence in nitrile, resulting in variable nitrile-dependent resting states. Strong coordination and considerable steric bulk of the carbene ligands facilitate selective initial binding of nitrile thereby forcing a heterocoupling pathway. In situ IR data suggests the initial binding of the nitrile resides in a rare, -bound conformation. Following nitrile coordination are a rate-determining hapticity shift of the nitrile and subsequent loss of carbene. Alkyne coordination then leads to heterooxidative coupling, insertion of the pendant alkyne, and reductive elimination to afford pyridine products.
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http://dx.doi.org/10.1021/om400666kDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4159214PMC
September 2013

Nickel-catalyzed cycloaddition of 1,3-dienes with 3-azetidinones and 3-oxetanones.

Angew Chem Int Ed Engl 2013 Nov 23;52(46):12161-5. Epub 2013 Sep 23.

Department of Chemistry, University of Utah, 315 South, 1400 East, Salt Lake City, Utah 84112-0850 (USA) http://www.chem.utah.edu/directory/faculty/louie.html.

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http://dx.doi.org/10.1002/anie.201306869DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4113093PMC
November 2013

The iron-catalyzed construction of 2-aminopyrimidines from alkynenitriles and cyanamides.

Chem Commun (Camb) 2013 Sep;49(70):7735-7

The University of Utah, 315 S. 1400 E. RM. 2020, Salt Lake City, UT 84102, USA.

Several cycloaddition catalysts and reagents were surveyed for their effectiveness toward cyclizing alkynenitriles with cyanamides. Catalytic amounts of FeI2, (iPr)PDAI and Zn were found to effectively catalyze the [2+2+2] cycloaddition of a variety of cyanamides and alkynenitriles to afford bicyclic 2-aminopyrimidines.
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http://dx.doi.org/10.1039/c3cc44422hDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4144345PMC
September 2013

The discovery of [Ni(NHC)RCN]2 species and their role as cycloaddition catalysts for the formation of pyridines.

J Am Chem Soc 2012 Sep 4;134(36):15154-62. Epub 2012 Sep 4.

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA.

The reaction of Ni(COD)(2), IPr, and nitrile affords dimeric [Ni(IPr)RCN](2) in high yields. X-ray analysis revealed these species display simultaneous η(1)- and η(2)-nitrile binding modes. These dimers are catalytically competent in the formation of pyridines from the cycloaddition of diynes and nitriles. Kinetic analysis showed the reaction to be first order in [Ni(IPr)RCN](2), zeroth order in added IPr, zeroth order in nitrile, and zeroth order in diyne. Extensive stoichiometric competition studies were performed, and selective incorporation of the exogenous, not dimer bound, nitrile was observed. Post cycloaddition, the dimeric state was found to be largely preserved. Nitrile and ligand exchange experiments were performed and found to be inoperative in the catalytic cycle. These observations suggest a mechanism whereby the catalyst is activated by partial dimer-opening followed by binding of exogenous nitrile and subsequent oxidative heterocoupling.
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http://dx.doi.org/10.1021/ja3075924DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3480329PMC
September 2012

Iron-catalyzed formation of 2-aminopyridines from diynes and cyanamides.

J Org Chem 2012 Sep 14;77(17):7555-63. Epub 2012 Aug 14.

Department of Chemistry, University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112-0850, USA.

Diynes and cyanamides undergo an iron-catalyzed [2 + 2 + 2] cycloaddition to form highly substituted 2-aminopyridines in an atom-efficient manner that is both high yielding and regioselective. This system was also used to cyclize two terminal alkynes and a cyanamide to afford a 2,4,6-trisubstituted pyridine product regioselectively.
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http://dx.doi.org/10.1021/jo3012418DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3480319PMC
September 2012

An expeditious route to eight-membered heterocycles by nickel-catalyzed cycloaddition: low-temperature C(sp)2-C(sp)3 bond cleavage.

Angew Chem Int Ed Engl 2012 Aug 17;51(34):8602-6. Epub 2012 Jul 17.

Department of Chemistry, University of Utah, 315 South, 1400 East, Salt Lake City, Utah 84112-0850, USA.

A cool break: 3-Azetidinone and a variety of diynes undergo a cycloaddition reaction catalyzed by Ni/IPr to give dihydroazocine compounds (see scheme; IPr=1,3-bis(2,6-diisopropylphenyl)imidazolidene). The reaction involves a challenging C(sp)2-C(sp)3 bond cleavage step, yet, surprisingly, proceeds at low temperature.
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http://dx.doi.org/10.1002/anie.201203521DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3557805PMC
August 2012

A single step approach to piperidines via Ni-catalyzed β-carbon elimination.

Org Lett 2012 Apr 2;14(8):2026-9. Epub 2012 Apr 2.

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84102, USA.

An easy and expeditious route to substituted piperidines is described. A Ni-phosphine complex was used as catalyst for [4 + 2] cycloaddition of 3-azetidinone and alkynes. The reaction has broad substrate scope and affords piperidines in excellent yields and excellent regioselectivity. In the reaction of an enantiopure azetidinone, complete retention of stereochemistry was observed.
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http://dx.doi.org/10.1021/ol300534jDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4138124PMC
April 2012

Palladium-catalyzed arylation of cyanamides.

Org Lett 2012 Jan 5;14(1):322-5. Epub 2011 Dec 5.

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA.

The cross-coupling of alkyl cyanamides with a number of aryl, heteroaryl, and vinyl halide and pseudohalide coupling partners has been developed via a modification of Pd-catalyzed amidation methods. The reactions proceed selectively under mild conditions with reasonable reaction times in moderate to excellent yields.
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http://dx.doi.org/10.1021/ol203069pDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4113087PMC
January 2012

Suzuki-Miyaura coupling of heteroaryl boronic acids and vinyl chlorides.

Chem Commun (Camb) 2012 Jan 14;48(2):203-5. Epub 2011 Nov 14.

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, UT 84112, USA.

A protocol for the Suzuki-Miyaura coupling of heteroaryl boronic acids and vinyl chlorides that minimizes protodeboronation is described. A combination of catalytic amounts of Pd(OAc)(2) and SPhos in conjunction with CsF in isopropanol effectively affords a variety of coupled products. Surprisingly, a dramatic temperature dependence in product selectivity was observed.
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http://dx.doi.org/10.1039/c1cc15990aDOI Listing
January 2012

Nickel-mediated cycloaddition by two sequential C-H activations.

Angew Chem Int Ed Engl 2011 Nov 27;50(46):10768-9. Epub 2011 Sep 27.

Department of Chemistry, University of Utah, Salt Lake City, UT 84112, USA.

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http://dx.doi.org/10.1002/anie.201103621DOI Listing
November 2011

A serendipitous discovery: nickel catalyst for the cycloaddition of diynes with unactivated nitriles.

Angew Chem Int Ed Engl 2011 Nov 20;50(45):10694-8. Epub 2011 Sep 20.

Department of Chemistry, University of Utah, 315 South, 1400 East, Salt Lake City, UT 84112-0850, USA.

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http://dx.doi.org/10.1002/anie.201104475DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3557808PMC
November 2011

Imidazolidene carboxylate bound MBPh4 complexes (M = Li, Na) and their relevance in transcarboxylation reactions.

J Org Chem 2011 Oct 27;76(20):8413-20. Epub 2011 Sep 27.

Department of Chemistry, Henry Eyring Building, University of Utah, 315 S. 1400 E, Salt Lake City, Utah 84112-0850, United States.

Combination of 1,3-bis(2,6-diisopropylphenyl)imidazolum-2-carboxylate (IPrCO(2)) with the Lewis acids MBPh(4), where M = Li or Na, provided two separate complexes. The crystal structures of these complexes revealed that coordination to NaBPh(4) yielded a dimeric species, yet coordination of IPrCO(2) with LiBPh(4) yielded a monomeric species. Combination of 1,3-bis(2,4,6-trimethylphenyl)imidazolum-2-carboxylate (IMesCO(2)) with LiBPh(4) also afforded a dimeric species that was similar in global structure to that of the IPrCO(2)+NaBPh(4) dimer. In all three cases, the cation of the organic salt was coordinated to the oxyanion of the zwitterionic carboxylate. Thermogravimetric analysis of the crystals demonstrated that decarboxylation occurred at lower temperatures than the decarboxylation temperature of the parent NHC·CO(2) (NHC = N-heterocyclic carbene). Kinetic analysis of the transcarboxylation of IPrCO(2) to acetophenone with NaBPh(4) to yield sodium benzoylacetate was performed. First-order dependences were observed for IPrCO(2) and acetophenone, whereas zero -order dependence was observed for NaBPh(4). Direct dicarboxylation was observed when I(t)BuCO(2) was added to MeCN in the absence of added MBPh(4).
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http://dx.doi.org/10.1021/jo201647bDOI Listing
October 2011

Nickel-Catalyzed [2+2+2] Cycloaddition of Diynes and Cyanamides.

European J Org Chem 2011 Jul;2011(20-21):3815-3824

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, USA.

A variety of bicyclic ,-disubstituted 2-aminopyridines have been prepared from diynes and cyanamides by nickel-catalyzed [2+2+2] cycloaddition reactions. The reactions proceeded at room temperature with low catalyst loading to afford 2-aminopyridines in good to excellent yields. The method is amenable to both internal and terminal diynes and proceeds in a regioselective manner. A number of cyanamides with diverse functional group tolerance were used. The intermolecular version employing 3-hexyne and -cyanopyrrolidine also afforded the desired ,-disubstituted 2-aminopyridine in good yield.
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http://dx.doi.org/10.1002/ejoc.201100428DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4208422PMC
July 2011

N-Heterocyclic Carbene Bound Nickel(I) Complexes and Their Roles in Catalysis.

Organometallics 2011 May;30(9):2546-2552

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850.

New paramagnetic Ni(I)(IMes)(2)X (IMes: 1,3-bis-(2,4,6-trimethylphenyl)-imidazol-2-ylidene) were prepared from the reaction of Ni(IMes)(2) with aryl halides. Products that would arise from oxidative addition were not observed. In contrast, Ni(II)(tmiy)(2)(X)(Ar) was formed from the oxidative addition of aryl halides to Ni bound by a sterically-less hindered NHC ligand, tmiy (tetramethylimidazol-2-ylidene). The paramagnetic Ni(I)(IMes)(2)X complexes were compared to known Ni(0) and Ni(II) catalysts for Kumada and Suzuki coupling reactions. Stoichiometric reactions between the Ni(I)(IMes)(2)X complexes with aryl halides and transmetallating agents were also evaluated.
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http://dx.doi.org/10.1021/om200090dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3092490PMC
May 2011

Iron-catalyzed cycloaddition of alkynenitriles and alkynes.

Org Lett 2011 Jun 10;13(11):2936-9. Epub 2011 May 10.

Department of Chemistry, University of Utah, Salt Lake City, Utah 84102, United States.

The combination of Fe(OAc)(2) and an electron-donating, sterically hindered pyridyl bisimine ligand catalyzes the cycloaddition of alkynenitriles and alkynes. A variety of substituted pyridines were obtained in good yields.
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http://dx.doi.org/10.1021/ol2009939DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3203642PMC
June 2011

Ni-catalyzed ketene cycloaddition: a system that resists the formation of decarbonylation side products.

J Am Chem Soc 2011 May 29;133(20):7719-21. Epub 2011 Apr 29.

Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-8450, USA.

Ni-phosphine complexes were used as catalysts for the cycloaddition of various ketenes and diynes. In general, 2,4-cyclohexadienones were formed instead of products arising from decarbonylation of the ketenes.
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http://dx.doi.org/10.1021/ja2007627DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3107595PMC
May 2011

Rhodium-catalyzed decarboxylative cycloaddition route to substituted anilines.

J Org Chem 2011 Jun 2;76(11):4686-91. Epub 2011 May 2.

Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, United States.

A convenient method for preparing substituted anilines via a Rh-catalyzed [2 + 2 + 2] cycloaddition reaction of diynes and 2-oxazolone was discovered. The initial cycloaddition adducts undergo facile decarboxylation of carbon dioxide to afford aniline products. Reaction conditions are mild, and only 3 mol % Rh catalyst is required. High regioselectivity was observed when an unsymmetrical diyne was used as a starting material.
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http://dx.doi.org/10.1021/jo200236hDOI Listing
June 2011

Nickel-catalyzed reactions of vinyl aziridines and aziridinylen-ynes.

Tetrahedron Lett 2008 Nov;49(48):6797-6799

University of Utah, Department of Chemistry, 315 South 1400 East, Salt Lake City, UT, 84112, USA.

Ni/NHC was found to catalyze the rearrangement of vinyl aziridines and aziridinylen-ynes under mild conditions.
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http://dx.doi.org/10.1016/j.tetlet.2008.09.056DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2598760PMC
November 2008
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