Showing papers by "Louis J. Farrugia published in 2012"
TL;DR: The WinGX suite provides a complete set of programs for the treatment of small-molecule single-crystal diffraction data, from data reduction and processing, structure solution, model refinement and visualization, and metric analysis of molecular geometry and crystal packing, to final report preparation in the form of a CIF.
Abstract: The WinGX suite provides a complete set of programs for the treatment of small-molecule single-crystal diffraction data, from data reduction and processing, structure solution, model refinement and visualization, and metric analysis of molecular geometry and crystal packing, to final report preparation in the form of a CIF. It includes several well known pieces of software and provides a repository for programs when the original authors no longer wish to, or are unable to, maintain them. It also provides menu items to execute external software, such as the SIR and SHELX suites of programs. The program ORTEP for Windows provides a graphical user interface (GUI) for the classic ORTEP program, which is the original software for the illustration of anisotropic displacement ellipsoids. The GUI code provides input capabilities for a wide variety of file formats, and extra functionality such as geometry calculations and ray-traced outputs. The programs WinGX and ORTEP for Windows have been distributed over the internet for about 15 years, and this article describes some of the more modern features of the programs.
9,479 citations
TL;DR: In this article, the experimental and theoretical charge densities in the sulfido-bridged cluster compounds Fe2(μ-S2)(CO)6 (1), Fe3(μ3-S)2(CO)9 (2), Mn2(m-S 2)(μ-CO)5(PPh3) (4) have been studied using the quantum theory of atoms in molecules methodology.
39 citations
TL;DR: Enantiopure, Boc-protected alkoxyamines 12 and 13, derived from the readily available homoallylic alcohols 4 via a reaction that involves either inversion or retention of configuration, undergo a diastereoselective Pd-catalyzed ring-closing carbonylative amidation to produce isoxazolidines 16/17.
Abstract: Enantiopure, Boc-protected alkoxyamines 12 and 13, derived from the readily available homoallylic alcohols 4 via a reaction that involves either inversion or retention of configuration, undergo a diastereoselective Pd-catalyzed ring-closing carbonylative amidation to produce isoxazolidines 16/17 (≤50:1 diastereoisomer ratio (d.r.)) that can be readily converted into the N-Boc-protected esters of β-amino-δ-hydroxy acids and their γ-substituted homologues 37. The key carbonylative cyclization proceeds through an unusual syn addition of the palladium and the nitrogen nucleophile across the C[DOUBLE BOND]C bond (19→21), as revealed by the reaction of 15, which afforded isoxazolidine 18 with high diastereoselectivity.
32 citations
TL;DR: The evidence strongly implicates the multipole model as the source of these spurious features and suggests that great caution should be applied in the interpretation of bond paths where the values of ρ(r(b)) and ∇(2)ρ( r(b))) are very low.
Abstract: In a recent publication in this journal, an experimental charge density analysis on the triruthenium cluster Ru3(CO)12 showed unusual C...C bond paths linking the axial carbonyl ligands [Gervasio, G.; Marabello, D.; Bianchi, R.; Forni, A. J. Phys. Chem. A2010, 114, 9368, hereafter GMBF]. These were also observed in one theoretical DFT calculation, and are associated with very low values of ρ(rb) and ∇2ρ(rb). Our independent experimental charge density analysis on Ru3(CO)12 is entirely consistent with GMBF and confirms the presence of these apparent weak interactions in the multipole model density. However, we conclusively demonstrate that these unusual C...C bond paths between the axial carbonyl ligands are in fact artifacts arising from the Hansen-Coppens multipole model, which is used to analyze the experimental data. Numerous relativistic and nonrelativistic gas-phase DFT calculations, using very extensive basis sets and with corrections for dispersion effects, uniformly fail to reproduce these intramo...
23 citations
TL;DR: A one-pot tandem process involving an Overman rearrangement, ring closing enyne metathesis and a hydrogen bonding directed Diels-Alder reaction has been developed for the efficient diastereoselective synthesis of functionalised amino substituted tetralin and indene ring systems.
18 citations
TL;DR: Stereoselective epoxidation and dihydroxylation of the syn-(4aS,10bS)-phenanthridone framework was investigated leading to the preparation of new analogues of 7-deoxypancratistatin.
Abstract: A new synthetic approach has been developed for the preparation of 7-deoxypancratistatin analogues bearing a syn-(4aS,10bS)-phenanthridone ring junction. A one-pot tandem process involving a substrate-directed Overman rearrangement and ring closing metathesis reaction was developed for the stereoselective synthesis of a carbocyclic allylic trichloroacetamide. Conversion to a 6-bromopiperonyl amide, followed by a Heck reaction generated a homoallylic alcohol and completed the syn-(4aS,10bS)-phenanthridone carbon skeleton. Stereoselective epoxidation and dihydroxylation of the syn-(4aS,10bS)-phenanthridone framework was then investigated leading to the preparation of new analogues of 7-deoxypancratistatin.
10 citations
TL;DR: The quality of methylene diphenyl diisocyanate (MDI) products can be compromised by the presence of color, presumed to arise from trace impurities as discussed by the authors.
Abstract: The quality of methylene diphenyl diisocyanate (MDI) products, which are valuable feedstocks in the industrial manufacture of polyurethanes, can be compromised by the presence of color, presumed to arise from trace impurities. One undesired branch in the synthesis chain originates with phosgenation of diaryl ureas, formed from reactions between aryl isocyanates and polyamine precursors. Subsequent key steps include, (i) breakdown of the primary compounds, substituted chloroformamidine-N-carbonyl chlorides (CCC), to give aryl isocyanide dichlorides, ArNCCl2, (ii) an apparent equilibrium connecting CCC with aryl carbodiimides, and (iii) the thermolysis of ArNCCl2 in the presence of MDI. Color formation is associated directly with the last process; it involves several events, including HCl elimination from reaction of ArNCCl2 and MDI, formation of carbon-centered radicals, and a contribution from oxidation at the methylene bridge.
4 citations
Book•
01 Jan 2012
TL;DR: More than just distance from Electron Density studies, the distance between charge density and electron density studies has also been discussed in this article, where a comparison between the molecular orbital and charge density picture is made.
Abstract: More than Just Distances from Electron Density Studies.- Modeling and Analysis of Hydrogen Atoms.- Charge Density Methods in Hydrogen Bond Studies.- Some Main Group Chemical Perceptions in the Light of Experimental Charge Density Investigations.- Electronic Structure and Chemical Properties of Lithium Organics Seen Through the Glasses of Charge Density.- Bond Orders in Metal-Metal Interactions Through Electron Density Analysis.- On the Nature of ss-Agostic Interactions: A Comparison Between the Molecular Orbital and Charge Density Picture.
2 citations
TL;DR: The conformation of the well-ordered cycloheptanone molecule, which normally undergoes facile pseudorotation, is unambiguously defined in the voids of the crystalline inclusion compound.
1 citations
TL;DR: In this paper, N-Boc-protected alkyloxyamines derived from homoallylic alcohols undergo a diastereoselective Pd-catalyzed ring-closing carbonylative amidation reaction to afford isoxazolidines that can be readily converted into β-amino-δ-hydroxy carboxylic acid esters.
Abstract: N-Boc-protected alkyloxyamines derived from homoallylic alcohols undergo a diastereoselective Pd-catalyzed ring-closing carbonylative amidation reaction to afford isoxazolidines that can be readily converted into N-Boc-protected β-amino-δ-hydroxy carboxylic acid esters by cleavage of the O—N bond with Mo(CO)6.
TL;DR: In this article, a one-pot tandem process involving an Overman rearrangement, ring closing enyne metathesis and a hydrogen bonding directed Diels-Alder reaction has been developed for the efficient diastereoselective synthesis of functionalised amino substituted tetralin and indene ring systems.
Abstract: A one-pot tandem process involving an Overman rearrangement, ring closing enyne metathesis and a hydrogen bonding directed Diels–Alder reaction has been developed for the efficient diastereoselective synthesis of functionalised amino substituted tetralin and indene ring systems.