Gerald B. Hammond

Bio: Gerald B. Hammond is an academic researcher from University of Louisville. The author has contributed to research in topics: Catalysis & Nucleophile. The author has an hindex of 43, co-authored 278 publications receiving 6387 citations. Previous affiliations of Gerald B. Hammond include University of Iowa & Dartmouth College.

Ligand Effects and Ligand Design in Homogeneous Gold(I) Catalysis

Abstract: Gold catalysis is considered one of the most important breakthroughs in organic synthesis during the past decade, but a rational understanding of ligand effects in gold catalysis is lacking. Most gold-catalyzed reactions go through three major stages: (i) electronic activation of alkyne (or allene) to generate a vinyl gold intermediate; (ii) protodeauration to generate the product and regenerate the cationic gold catalyst; (iii) decay of the active gold catalyst. Our research provides a clearer understanding of how ligands influence each of the three stages in the gold catalytic cycle. What is even more important, by not focusing on a particular gold-catalyzed reaction, we have been able to categorize most gold-catalyzed reactions and propose a ligand design protocol for each category of gold-catalyzed reactions.

Recent advances in the isolation and reactivity of organogold complexes

Abstract: Homogeneous gold catalysis has been one of the most active research fields in organic chemistry for more than a decade, and it has been also among the most efficient methodologies for forming carbon–carbon or carbon–heteroatom bonds. Recently, a number of organogold intermediates were isolated from stoichiometric reactions, which helps to better understand the mechanisms. Meanwhile, the reactivity of organogold compounds has been attracting the attention of organic chemists in the field. This tutorial review collects the most recent advances in the isolation and reactivity of organogold compounds that may help to open new directions in homogenous gold catalysis.

Synthesis and structural characterization of stable organogold(I) compounds. Evidence for the mechanism of gold-catalyzed cyclizations.

Abstract: The vast majority of homogeneous Au-catalyzed reactions have exploited the propensity of Au to activate unsaturated carbon−carbon bonds as electrophiles. It is generally assumed that a nucleophile attacks a gold-activated carbon−carbon multiple bond to give an alkenyl Au intermediate, notwithstanding the fact that these intermediates are hitherto unknown. We have obtained room temperature stable γ-lactone gold(I) complexes through the reaction of cationic Au(I) reagents with allenoates, under mild conditions. The reactions of one such complex with electrophiles yielded the expected products of Au-catalyzed cyclizations. These results furnish experimental evidence for the mechanism of Au-catalyzed cyclizations.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Introduction of Fluorine and Fluorine-Containing Functional Groups

Abstract: Over the past decade, the most significant, conceptual advances in the field of fluorination were enabled most prominently by organo- and transition-metal catalysis. The most challenging transformation remains the formation of the parent C-F bond, primarily as a consequence of the high hydration energy of fluoride, strong metal-fluorine bonds, and highly polarized bonds to fluorine. Most fluorination reactions still lack generality, predictability, and cost-efficiency. Despite all current limitations, modern fluorination methods have made fluorinated molecules more readily available than ever before and have begun to have an impact on research areas that do not require large amounts of material, such as drug discovery and positron emission tomography. This Review gives a brief summary of conventional fluorination reactions, including those reactions that introduce fluorinated functional groups, and focuses on modern developments in the field.

Hydroamination: direct addition of amines to alkenes and alkynes.

Abstract: 8.4.5. Nitromercuration Reactions 3878 9. Hydroamination of Alkenes and Alkynes under Microwave Irradiation 3878 * To whom correspondence should be addressed. Phone: +49 241 8

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg