Browse
Submit Data
Databases
API
Help

Dataset Information

19 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

The Transition Metal Catalyzed [π2s + π2s + σ2s + σ2s] Pericyclic Reaction: Woodward-Hoffmann Rules, Aromaticity, and Electron Flow.

ABSTRACT: We have shown that the fundamental step responsible for enantioinduction in the inner-sphere asymmetric Tsuji allylic alkylation is C-C bond formation through a seven-membered pericyclic transition state. We employ an extensive series of quantum mechanics (QM) calculations to delineate how the electronic structure of the Pd-catalyzed C-C bond forming process controls the reaction. Phase inversion introduced by d orbitals renders the Pd-catalyzed [π2s + π2s + σ2s + σ2s] reaction symmetry-allowed in the ground state, proceeding through a transition state with Craig-Möbius-like σ-aromaticity. Lastly, we connect QM to fundamental valence bonding concepts by deriving an ab initio "arrow-pushing" mechanism that describes the flow of electron density through the reaction.

SUBMITTER: Cusumano AQ

PROVIDER: S-EPMC8549492 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

Tracking the Transition from Pericyclic to Pseudopericyclic Reaction Mechanisms Using Multicenter Electron Delocalization Analysis: The [1,3] Sigmatropic Rearrangement.

Project description:Herein, the power of multicenter electron delocalization analysis to elucidate the intricacies of concerted reaction mechanisms is brought to light by tracking the transition of [1,3] sigmatropic rearrangements from the high-barrier pericyclic mechanism in 1-butene to the barrierless pseudopericyclic mechanism in 1,2-diamino-1-nitrosooxyethane. This transition has been progressively achieved by substituting the migrating group, changing the donor and acceptor atoms, and functionalizing the alkene unit with weak and strong electron-donating and electron-withdrawing groups. Fourteen [1,3] sigmatropic reactions with electronic energy barriers ranging from 1 to 89 kcal/mol have been investigated. A very good correlation has been found between the barrier and the four-center electron delocalization at the transition state, the latter calculated for the atoms involved in the four-centered ring adduct formed along the reaction path. Surprisingly, the barrier has been found to be independent of the bond strength between the migrating group and the donor atom so that only the changes induced in the multicenter bonding control the kinetics of the reaction. Additional insights into the effect of atom substitution and group functionalization have also been extracted from the analysis of the multicenter electron delocalization profiles along the reaction path and qualitatively supported by the topological analysis of the electron density.

| S-EPMC8693182 | biostudies-literature

Synthesis of hindered biphenyls by sequential non-transition metal-catalyzed reaction/palladium-catalyzed cross-couplings.

Project description:The sequential reaction of 1,2-dihalobenzenes with aryl lithiums followed by palladium-catalyzed cross-coupling reactions with Grignard reagents and arylboronic acids is described. This sequential reaction provides a convenient and expeditious access to tri-ortho substituted biaryl derivatives.

| S-EPMC2350223 | biostudies-literature

Photoredox Catalysis Unlocks Single-Electron Elementary Steps in Transition Metal Catalyzed Cross-Coupling.

Project description:Since initial reports, cross-coupling technologies employing photoredox catalysts to access novel reactivity have developed with increasing pace. In this Outlook, prominent examples from the recent literature are organized on the basis of the elementary transformation enabled by photoredox catalysis and are discussed in the context of relevant historical precedent in stoichiometric organometallic chemistry. This treatment allows mechanistic similarities inherent to odd-electron transition metal reactivity to be generalized to a set of lessons for future reaction development.

| S-EPMC4882737 | biostudies-other

Pericyclic reactions catalyzed by chorismate-utilizing enzymes.

Project description:One of the fundamental questions of enzymology is how catalytic power is derived. This review focuses on recent developments in the structure--function relationships of chorismate-utilizing enzymes involved in siderophore biosynthesis to provide insight into the biocatalysis of pericyclic reactions. Specifically, salicylate synthesis by the two-enzyme pathway in Pseudomonas aeruginosa is examined. The isochorismate-pyruvate lyase is discussed in the context of its homologues, the chorismate mutases, and the isochorismate synthase is compared to its homologues in the MST family (menaquinone, siderophore, or tryptophan biosynthesis) of enzymes. The tentative conclusion is that the activities observed cannot be reconciled by inspection of the active site participants alone. Instead, individual activities must arise from unique dynamic properties of each enzyme that are tuned to promote specific chemistries.

| S-EPMC3164438 | biostudies-literature

Computational Insight Concerning Catalytic Decision Points of the Transition Metal Catalyzed [2 + 2 + 1] Cyclocarbonylation Reaction of Allenes.

Project description:Rhodium and molybdenum catalyzed allenic [2 + 2 + 1] cycloaddition reactions give 4-alkylidene and ?-alkylidene cylopentenones, respectively. The selective reaction of one double bond of the allene over another is controlled by the transition metal and not the substrate structure. Calculations were performed to explain this unique control element using the B3LYP functional as implemented in Gaussian 03. The 6-31G(d) basis set was applied to all elements except rhodium, which is described with the LANL2 effective core potential and the LANL2DZ basis set. The product-determining step for both reaction pathways is oxidative addition of the metal to the alkynyl allene to form the corresponding metallocycles B and B'. The transition state calculations strongly suggest that geometry constraints imposed by the metal in the transition state are the key controlling factor of the double bond selectivity. The transition state structure of rhodium-catalyzed oxidative addition has a distorted square planar geometry that affords a lower transition state energy when coordinated to the distal double bond of the allene. In turn, the distorted trigonal bipyramidal geometry of molybdenum in the transition state structure imposes conformational constraints upon binding to the distal double on the allene and thus leads to the energetically preferred complexation and reaction with the proximal double bond.

| S-EPMC4441411 | biostudies-literature

Extension of the Simmons-Smith reaction to metal-carbynes: efficient synthesis of metallacyclopropenes with σ-aromaticity.

Project description:The Simmons-Smith reaction offers a direct route for conversion of an alkene into a cyclopropane with a zinc carbenoid as the active intermediate. Zinc carbenoids, however, have never delivered a methylene unit to substrates with metal-carbon multiple bonds. Herein, we describe this type of reaction and the construction of three-membered rings has now been applied in organometallic systems by combining classical zinc carbenoid reagents with a range of structurally and electronically diverse metal carbynes. A variety of metallacyclopropene derivatives prepared in this way represent rare examples with σ-aromaticity in an unsaturated three-membered ring. The structures of such products are supported by experimental observations and theoretical calculations.

| S-EPMC8162146 | biostudies-literature

Metal-Free ATRP Catalyzed by Visible Light in Continuous Flow.

Project description:ATRP of methyl methacrylate catalyzed by Eosin Y, an inexpensive and an environmental benign dye, was performed in a continuous flow reactor made of FEP tubing and irradiated by visible light green LEDs. The reaction under flow conditions was significantly more rapid and controlled compared to that in batch giving 90% of polymerization after only 3 h of irradiation. The formed polymers in flow have M n measured by GPC and DOSY NMR in accordance with the theoretical values and show low dispersities (Ð < 1.5). The livingness of the polymers has been confirmed by LED on and LED off experiments and by the synthesis of block copolymers. The protocol described herein serves as a "proof of concept" of using Eosin Y as a photocatalyst for controlled polymerization and of using 1D and 2D NMR for polymer characterization. The protocol could be replicated in the future for other reversible-deactivation radical polymerizations.

| S-EPMC7505802 | biostudies-literature

Lewis acid catalyzed inverse-electron-demand Diels-Alder reaction of tropones.

Project description:Lewis acid catalyzed inverse-electron-demand Diels-Alder reaction of tropone derivatives was developed. Up to 97% ee was obtained for the chiral dinucleus BINOL-aluminum complex catalyzed reaction between tropones and ketene diethyl acetal to give bicyclo[3.2.2] ring structures, which opens up a unique way of making chiral seven-membered rings.

| S-EPMC2810398 | biostudies-literature

Evaluating transition-metal-catalyzed transformations for the synthesis of laulimalide.

Project description:Laulimalide is a structurally unique 20-membered marine macrolide displaying microtubule stabilizing activity similar to that of paclitaxel and the epothilones. The use of atom-economical transformations such as a Rh-catalyzed cycloisomerization to form the endocyclic dihydropyran, a dinuclear Zn-catalyzed asymmetric glycolate aldol reaction to prepare the syn 1,2-diol, and an intramolecular Ru-catalyzed alkene-alkyne coupling to build the macrocycle enabled us to synthesize laulimalide via an efficient and convergent pathway. The designed synthetic route also allowed us to prepare an analogue of the natural product that possesses significant cytotoxic activity.

| S-EPMC2791108 | biostudies-literature

Investigation of transition metal-catalyzed nitrene transfer reactions in water.

Project description:Transition metal-catalyzed nitrene transfer is a powerful method for incorporating new CN bonds into relatively unfunctionalized scaffolds. In this communication, we report the first examples of site- and chemoselective CH bond amination reactions in aqueous media. The unexpected ability to employ water as the solvent in these reactions is advantageous in that it eliminates toxic solvent use and enables reactions to be run at increased concentrations with lower oxidant loadings. Using water as the reaction medium has potential to expand the scope of nitrene transfer to encompass a variety of biomolecules and highly polar substrates, as well as enable pH control over the site-selectivity of CH bond amination.

| S-EPMC6657797 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data