Benjamin Ketz - Academia.edu (original) (raw)

Papers by Benjamin Ketz

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 241776: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Chemical Communications, 2005

Experimental General Considerations. All organometallic reactions were performed under an inert a... more Experimental General Considerations. All organometallic reactions were performed under an inert atmosphere of N 2 using standard Schlenk line techniques. Degassing of solvents was achieved via multiple freeze pump thaw cycles. Mesityl imidazole, 2,6-Diisopropyl-phenyl imidazole, and 3-Mesityl-1-(2-oxo-2-phenyl-ethyl)-imidazolium bromide are literature compounds. 1,2 2,6-Diisopropyl-phenyl imidazole was purified via column chromatography (eluting with 9 hexane : 1 CH 2 Cl 2 then 75 hexane : 15 CH 2 Cl 2 : 10 acetone), filtering through activated charcoal, and recrystallizing from heptane. 2-Bromoacetophenone was used as received from Aldrich, and NaN(TMS) 2 was purchased from Aldrich and stored in an inert atmosphere. Ni(COD) 2 was purchased from Strem and stored in a glovebox freezer (-30 °C). Celite was baked out at 140 °C prior to use. Pyridine was purchased as an extra dry solvent from Acros, degassed, and stored over activated molecular sieves. PMAO-IP was purchased from Akzo Nobel and dried in vacuo prior to use; it is refered to as MAO in this report. Chlorobenzene was dried over calcium hydride, degassed, and vacuum transferred. Other reaction solvents were purified by passing through a column of either alumina or molecular sieves and degassing. Deuterated benzene was purchased from Acros, dried over sodium benzophenone, degassed, and vacuum transferred. Deuterated chloroform and bromobenzene were purchased from Acros and used as received. NMR spectra were taken on a Varian Unity Inova 500 MHz NMR, a Varian Unity Inova 600 MHz NMR (15 N NMR only), and a Varian Unity Inova 300 MHz NMR (polymer NMRs). Chemical shifts were referenced to residual solvent peak: chloroform (7.26 ppm, 77 ppm), benzene (7.15 ppm, 128 ppm), bromobenzene (at 100 °C, furthest upfield peak, 7 ppm, 123 ppm). Where applicable, peak assignments were made by gHSQC, gHMBC, gCOSY, and g 15 NHMBC. NMR spectra of polymers were taken of saturated polymer solutions at 100 °C. For 13 C NMR spectra of polymers, 80% odichlorobenzene / 20% d-benzene with a minimal amount of Cr(acac) 3 was used as a solvent, and dbromobenzene was used for 1 H spectra. 13 C spectra were taken with a 90° pulse and inverse gated decoupling. Elemental analyses were performed by Atlantic Microlab, Inc. in Norcross, GA 30091. High temp GPC analysis was performed on a Polymer Laboratories 220 GPC equipped with a refractometer detector; the polystyrene standard peak molecular weights were converted to polyethylene molecular weights. 3 3-(2,6-Diisopropyl-phenyl)-1-(2-oxo-2-phenyl-ethyl)-imidazolium bromide, 1b. 2-Bromoacetophenone (1.84 g) was dissolved in THF (20 mL) and transferred to a solution of 2,6-Diisopropylphenyl imidazole (2.0 g) in THF (20 mL). THF (10 mL) was used to complete the transfer, and the rxn was stirred 4 hr under N 2 , being concentrated to 25 mL. Ether (30 mL) was layered on top, and after 2 days the mixture was filtered to afford off-white powder and crystals. This was recrystallized from CH 2 Cl 2 layered with THF and ether. The crystals were redissolved in CH 2 Cl 2 , mixed with activated charcoal, filtered, and recrystallized in the same manner to afford clear white crystals, which were dried in vacuo (3.4 g, 91%).

ChemInform Abstract: Substituent Effects on the Regioselectivity of the Baeyer-Villiger Oxidation of 7-Oxabicyclo(2.2.1)heptan-2-ones

ChemInform, 1993

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Tetrahedron Letters, 2000

The result of the substitution of trityl chlorides with Grignard reagents was found to be highly ... more The result of the substitution of trityl chlorides with Grignard reagents was found to be highly dependent on the solvent and the nature of the substituents on the trityl group. In THF, electron donating substituents were found to give high yields of Grignard addition while electron withdrawing substituents were found to give mostly reduction to the corresponding triphenyl methane via hydride abstraction from the solvent.

Organometallics, 2004

A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the c... more A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the complex (NHC-enolate)Pd(allyl). At elevated temperatures in acetonitrile, the allyl ligand undergoes a stereoselective η 3 -η 1 -η 3 isomerization in an associative process that is first order in CD 3 CN with ∆H q ) 13.5 ( 0.7 kcal mol -1 and ∆S q ) -17 ( 2 eu. This complex reacts with electrophiles (HCl, CH 3 I) at the enolate position.

Organometallics, 2004

A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the c... more A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the complex (NHC-enolate)Pd(allyl). At elevated temperatures in acetonitrile, the allyl ligand undergoes a stereoselective η 3 -η 1 -η 3 isomerization in an associative process that is first order in CD 3 CN with ∆H q ) 13.5 ( 0.7 kcal mol -1 and ∆S q ) -17 ( 2 eu. This complex reacts with electrophiles (HCl, CH 3 I) at the enolate position.

Synthesis, structure, and olefin polymerization with nickel(ii) N-heterocyclic carbene enolates

Chemical Communications, 2005

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

CCDC 241776: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Chemical Communications, 2005

Experimental General Considerations. All organometallic reactions were performed under an inert a... more Experimental General Considerations. All organometallic reactions were performed under an inert atmosphere of N 2 using standard Schlenk line techniques. Degassing of solvents was achieved via multiple freeze pump thaw cycles. Mesityl imidazole, 2,6-Diisopropyl-phenyl imidazole, and 3-Mesityl-1-(2-oxo-2-phenyl-ethyl)-imidazolium bromide are literature compounds. 1,2 2,6-Diisopropyl-phenyl imidazole was purified via column chromatography (eluting with 9 hexane : 1 CH 2 Cl 2 then 75 hexane : 15 CH 2 Cl 2 : 10 acetone), filtering through activated charcoal, and recrystallizing from heptane. 2-Bromoacetophenone was used as received from Aldrich, and NaN(TMS) 2 was purchased from Aldrich and stored in an inert atmosphere. Ni(COD) 2 was purchased from Strem and stored in a glovebox freezer (-30 °C). Celite was baked out at 140 °C prior to use. Pyridine was purchased as an extra dry solvent from Acros, degassed, and stored over activated molecular sieves. PMAO-IP was purchased from Akzo Nobel and dried in vacuo prior to use; it is refered to as MAO in this report. Chlorobenzene was dried over calcium hydride, degassed, and vacuum transferred. Other reaction solvents were purified by passing through a column of either alumina or molecular sieves and degassing. Deuterated benzene was purchased from Acros, dried over sodium benzophenone, degassed, and vacuum transferred. Deuterated chloroform and bromobenzene were purchased from Acros and used as received. NMR spectra were taken on a Varian Unity Inova 500 MHz NMR, a Varian Unity Inova 600 MHz NMR (15 N NMR only), and a Varian Unity Inova 300 MHz NMR (polymer NMRs). Chemical shifts were referenced to residual solvent peak: chloroform (7.26 ppm, 77 ppm), benzene (7.15 ppm, 128 ppm), bromobenzene (at 100 °C, furthest upfield peak, 7 ppm, 123 ppm). Where applicable, peak assignments were made by gHSQC, gHMBC, gCOSY, and g 15 NHMBC. NMR spectra of polymers were taken of saturated polymer solutions at 100 °C. For 13 C NMR spectra of polymers, 80% odichlorobenzene / 20% d-benzene with a minimal amount of Cr(acac) 3 was used as a solvent, and dbromobenzene was used for 1 H spectra. 13 C spectra were taken with a 90° pulse and inverse gated decoupling. Elemental analyses were performed by Atlantic Microlab, Inc. in Norcross, GA 30091. High temp GPC analysis was performed on a Polymer Laboratories 220 GPC equipped with a refractometer detector; the polystyrene standard peak molecular weights were converted to polyethylene molecular weights. 3 3-(2,6-Diisopropyl-phenyl)-1-(2-oxo-2-phenyl-ethyl)-imidazolium bromide, 1b. 2-Bromoacetophenone (1.84 g) was dissolved in THF (20 mL) and transferred to a solution of 2,6-Diisopropylphenyl imidazole (2.0 g) in THF (20 mL). THF (10 mL) was used to complete the transfer, and the rxn was stirred 4 hr under N 2 , being concentrated to 25 mL. Ether (30 mL) was layered on top, and after 2 days the mixture was filtered to afford off-white powder and crystals. This was recrystallized from CH 2 Cl 2 layered with THF and ether. The crystals were redissolved in CH 2 Cl 2 , mixed with activated charcoal, filtered, and recrystallized in the same manner to afford clear white crystals, which were dried in vacuo (3.4 g, 91%).

ChemInform Abstract: Substituent Effects on the Regioselectivity of the Baeyer-Villiger Oxidation of 7-Oxabicyclo(2.2.1)heptan-2-ones

ChemInform, 1993

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Tetrahedron Letters, 2000

The result of the substitution of trityl chlorides with Grignard reagents was found to be highly ... more The result of the substitution of trityl chlorides with Grignard reagents was found to be highly dependent on the solvent and the nature of the substituents on the trityl group. In THF, electron donating substituents were found to give high yields of Grignard addition while electron withdrawing substituents were found to give mostly reduction to the corresponding triphenyl methane via hydride abstraction from the solvent.

Organometallics, 2004

A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the c... more A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the complex (NHC-enolate)Pd(allyl). At elevated temperatures in acetonitrile, the allyl ligand undergoes a stereoselective η 3 -η 1 -η 3 isomerization in an associative process that is first order in CD 3 CN with ∆H q ) 13.5 ( 0.7 kcal mol -1 and ∆S q ) -17 ( 2 eu. This complex reacts with electrophiles (HCl, CH 3 I) at the enolate position.

Organometallics, 2004

A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the c... more A novel anionic N-heterocyclic carbene was prepared and ligated to [Pd(allyl)Cl] 2 to yield the complex (NHC-enolate)Pd(allyl). At elevated temperatures in acetonitrile, the allyl ligand undergoes a stereoselective η 3 -η 1 -η 3 isomerization in an associative process that is first order in CD 3 CN with ∆H q ) 13.5 ( 0.7 kcal mol -1 and ∆S q ) -17 ( 2 eu. This complex reacts with electrophiles (HCl, CH 3 I) at the enolate position.

Synthesis, structure, and olefin polymerization with nickel(ii) N-heterocyclic carbene enolates

Chemical Communications, 2005