Subtopic Deep Dive
Asymmetric Epoxidation Mechanisms
Research Guide
What is Asymmetric Epoxidation Mechanisms?
Asymmetric epoxidation mechanisms elucidate stereocontrol in reactions like Sharpless epoxidation using titanium-tartrate catalysts and chiral modifiers for enantioselective synthesis of epoxides.
Sharpless and Woodard (1983) proposed the mechanism for titanium-tartrate catalyzed asymmetric epoxidation of allylic alcohols (151 citations). Aggarwal et al. (1998) detailed stereoelectronic effects in sulfur ylide epoxidations with chiral 1,3-oxathianes (127 citations). Davis et al. (2014) reviewed organocatalytic variants, covering scope and mechanisms (144 citations). Over 1,000 papers explore these mechanisms since 1980.
Why It Matters
Chiral epoxides from asymmetric epoxidation serve as key intermediates in synthesizing pharmaceuticals like statins and antiviral drugs. Sharpless epoxidation (Sharpless and Woodard, 1983) enables predictable stereocontrol for industrial-scale production of enantiopure building blocks. Organocatalytic methods by Jørgensen (Davis et al., 2014) and sulfur ylide approaches by Aggarwal (Aggarwal et al., 1998; Illa et al., 2013) reduce catalyst costs and expand substrate scope for green chemistry applications in agrochemicals and materials.
Key Research Challenges
Elucidating Transition States
Determining exact geometries in titanium-tartrate complexes remains difficult due to fluxional species observed via spectroscopy. Sharpless and Woodard (1983) proposed models, but dynamic NMR and computation are needed for validation. Aggarwal et al. (2003) highlighted dual roles of ammonium salts complicating mechanistic probes.
Expanding Substrate Scope
Achieving high enantioselectivity beyond allylic alcohols challenges variant methods. Katsuki and Martín (1996) optimized Sharpless conditions, yet non-allylic alkenes show lower ee values. Davis et al. (2014) noted limitations in organocatalytic epoxidations for electron-deficient substrates.
Catalyst Efficiency Optimization
Balancing turnover numbers with selectivity requires precise chiral ligand design. Aggarwal et al. (1998) used 1,3-oxathianes for aldehydes, but scalability issues persist. Illa et al. (2013) mapped selectivities with cheap sulfides, revealing diastereo- and enantiocontrol dependencies.
Essential Papers
On the mechanism of titanium-tartrate catalyzed asymmetric epoxidation
K. Barry Sharpless, Scott S. Woodard · 1983 · Pure and Applied Chemistry · 151 citations
Abstract
Asymmetric Organocatalytic Epoxidations: Reactions, Scope, Mechanisms, and Applications
Rebecca L. Davis, Julian Stiller, Tricia Naicker et al. · 2014 · Angewandte Chemie International Edition · 144 citations
Abstract Chiral epoxides serve as versatile building blocks in the synthesis of complex organic frameworks. The high strain imposed by the three‐membered ring system makes epoxides prone to a varie...
Part I: Nitroalkenes in the synthesis of heterocyclic compounds
Azim Ziyaei Halimehjani, Irishi N. N. Namboothiri, Seyyed Emad Hooshmand · 2014 · RSC Advances · 133 citations
The applications of nitroalkenes in the synthesis of three- to five-membered O, N and S-heterocycles, including natural products are investigated in this review. These heterocyclic compounds were s...
Catalytic Asymmetric Epoxidation of Aldehydes. Optimization, Mechanism, and Discovery of Stereoelectronic Control Involving a Combination of Anomeric and Cieplak Effects in Sulfur Ylide Epoxidations with Chiral 1,3-Oxathianes
Varinder K. Aggarwal, J. Gair Ford, Sı́lvia Fonquerna et al. · 1998 · Journal of the American Chemical Society · 127 citations
A range of 1,3-oxathianes based on camphorsulfonic acid have been prepared and tested in the catalytic asymmetric epoxidation of carbonyl compounds. It was found that the 1,3-oxathiane derived from...
Practical and Highly Selective Sulfur Ylide-Mediated Asymmetric Epoxidations and Aziridinations Using a Cheap and Readily Available Chiral Sulfide: Extensive Studies To Map Out Scope, Limitations, and Rationalization of Diastereo- and Enantioselectivities
Ona Illa, Mariam Namutebi, Chandreyee Saha et al. · 2013 · Journal of the American Chemical Society · 114 citations
The chiral sulfide, isothiocineole, has been synthesized in one step from elemental sulfur, γ-terpinene, and limonene in 61% yield. A mechanism involving radical intermediates for this reaction is ...
New Insights in the Mechanism of Amine Catalyzed Epoxidation: Dual Role of Protonated Ammonium Salts as Both Phase Transfer Catalysts and Activators of Oxone
Varinder K. Aggarwal, Chrystel Lopin‐Bon, Franck Sandrinelli · 2003 · Journal of the American Chemical Society · 90 citations
Amines have previously been reported to catalyze the epoxidation of alkenes using Oxone (2KHSO(5)+KHSO(4)+K(2)SO(4)), and significant levels of asymmetric induction were observed. From screening a ...
Asymmetric Epoxidation of Allylic Alcohols: the Katsuki–Sharpless Epoxidation Reaction
Tsutomu Katsuki, Victor S. Martı́n · 1996 · Organic reactions · 87 citations
Abstract In 1980, Sharpless and Katsuki discovered a system for the asymmetric epoxidation of primary allylic alcohols that utilizes Ti(OPr‐ i ) 4 , a dialkyl tartrate as a chiral ligand, and tert ...
Reading Guide
Foundational Papers
Start with Sharpless and Woodard (1983, 151 citations) for titanium-tartrate mechanism core. Follow with Aggarwal et al. (1998, 127 citations) for sulfur ylide stereoelectronics and Katsuki and Martín (1996, 87 citations) for practical Sharpless optimization.
Recent Advances
Davis et al. (2014, 144 citations) for organocatalytic scope. Illa et al. (2013, 114 citations) for scalable sulfide catalysts. Zhao et al. (2007, 70 citations) for amine-catalyzed enal epoxidations.
Core Methods
Titanium-tartrate with tBuOOH (Sharpless). Sulfur ylides from chiral sulfides (Aggarwal). Amine/organocatalytic with Oxone or peroxides (Jørgensen, Córdova). Spectroscopic (NMR) and DFT validation of TS.
How PapersFlow Helps You Research Asymmetric Epoxidation Mechanisms
Discover & Search
Research Agent uses searchPapers with query 'Sharpless epoxidation mechanism titanium tartrate' to retrieve Sharpless and Woodard (1983), then citationGraph reveals 151 citing papers including Aggarwal variants, while findSimilarPapers expands to organocatalytic mechanisms like Davis et al. (2014). exaSearch uncovers computational studies on transition states from 250M+ OpenAlex papers.
Analyze & Verify
Analysis Agent applies readPaperContent to parse Sharpless and Woodard (1983) abstracts for transition state models, then verifyResponse with CoVe cross-checks claims against Aggarwal et al. (1998) stereoelectronic effects. runPythonAnalysis plots ee values vs. temperature from extracted data using pandas, with GRADE scoring mechanistic evidence reliability.
Synthesize & Write
Synthesis Agent detects gaps in substrate scope between Sharpless (1983) and organocatalytic methods (Davis et al., 2014), flagging contradictions in ylide mechanisms. Writing Agent uses latexEditText to draft reaction schemes, latexSyncCitations for 10+ references, and latexCompile for publication-ready reviews; exportMermaid visualizes transition state diagrams.
Use Cases
"Analyze ee trends in sulfur ylide epoxidations from Aggarwal papers"
Research Agent → searchPapers 'Aggarwal sulfur ylide epoxidation' → Analysis Agent → readPaperContent (Aggarwal 1998, Illa 2013) → runPythonAnalysis (pandas scatter plot of ee vs. substrate) → matplotlib output of selectivity heatmap.
"Write LaTeX review on Sharpless mechanism variants"
Synthesis Agent → gap detection (Sharpless 1983 vs. Davis 2014) → Writing Agent → latexEditText (mechanism section) → latexSyncCitations (10 papers) → latexCompile → PDF with TikZ epoxide schemes.
"Find code for computational modeling of epoxidation TS"
Research Agent → searchPapers 'asymmetric epoxidation DFT computation' → Code Discovery → paperExtractUrls → paperFindGithubRepo → githubRepoInspect → Gaussian input files for titanium-tartrate TS optimization.
Automated Workflows
Deep Research workflow scans 50+ papers on 'asymmetric epoxidation mechanisms' via searchPapers → citationGraph → structured report with GRADE-scored mechanisms from Sharpless (1983) to Aggarwal (2013). DeepScan applies 7-step CoVe analysis to verify transition states in Katsuki–Sharpless (Katsuki and Martín, 1996), checkpointing spectral evidence. Theorizer generates hypotheses on organocatalytic dual activation from Davis et al. (2014) data.
Frequently Asked Questions
What defines asymmetric epoxidation mechanisms?
Mechanisms explain stereocontrol in epoxidations using chiral catalysts like titanium-tartrate (Sharpless and Woodard, 1983) or sulfur ylides (Aggarwal et al., 1998), focusing on transition states for enantioselectivity.
What are key methods in asymmetric epoxidation?
Sharpless epoxidation uses Ti(OiPr)4, tartrate, and tBuOOH for allylic alcohols (Sharpless and Woodard, 1983; Katsuki and Martín, 1996). Organocatalytic methods employ amines or imidazolidinones with Oxone (Zhao et al., 2007; Davis et al., 2014). Sulfur ylide approaches use chiral sulfides for aldehydes (Aggarwal et al., 1998; Illa et al., 2013).
What are the most cited papers?
Sharpless and Woodard (1983, 151 citations) on titanium-tartrate mechanism. Davis et al. (2014, 144 citations) on organocatalytic epoxidations. Aggarwal et al. (1998, 127 citations) on sulfur ylide stereocontrol.
What open problems exist?
Predicting selectivities for non-allylic substrates and scaling cheap catalysts like isothiocineole (Illa et al., 2013). Resolving fluxional Ti-complex dynamics beyond Sharpless model (1983) via advanced computation.
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