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What Is Selectfluor?
Selectfluor (CAS 140681-55-6) is a electrophilic fluorinating reagent with the molecular formula C7H14B2ClF2N2 and molecular weight 212.86 g/mol. [001]
Physical and Chemical Properties
| Property | Value | Source |
|---|---|---|
| CAS Number | 140681-55-6 | |
| Molecular Formula | C7H14B2ClF2N2 | |
| Molecular Weight | 212.86 g/mol |
How It Works
Selectfluor activates carboxylic acids toward nucleophilic attack by amines (or alcohols) via formation of an O-acylisourea intermediate. In the first step, the carboxylate attacks the central carbon of the carbodiimide (R-N=C=N-R'), forming an unstable O-acylisourea. This activated ester is highly reactive toward amines — the amine attacks the carbonyl carbon, displacing the urea byproduct and forming the amide bond. With EDC·HCl, the urea byproduct is water-soluble (due to the tertiary amine moiety), enabling simple aqueous workup — a key advantage over DCC whose urea byproduct (DCU) requires filtration. When used with additives: HOBt or HOAt (1.1 eq) suppresses racemization by converting the O-acylisourea to the less reactive but more stereoretentive active ester. NHS esters (via EDC/NHS) are stable enough for two-step bioconjugation protocols. The reaction is typically run at pH 5-6 (optimal for carbodiimide activation) in water or DMF, 0 °C to rt, 2-24 h. Key limitation: O→N acyl migration can produce inactive N-acylurea at low amine concentrations — add excess amine or nucleophilic catalyst to suppress this side reaction.
Key Applications
- Electrophilic Fluorination of C-H & C=C Bonds: Selectfluor (Banks, 1992) is the most widely used electrophilic fluorinating reagent — commercialized as a bench-stable crystalline solid (cf. explosive F2 gas). Transfers F+ to enolates, enamines, electron-rich aromatics, and alkenes. Typical: 1.0-1.2 eq in MeCN, rt to 80C. Used for late-stage fluorination of pharmaceutical candidates where electrophilic aromatic substitution is the only viable approach. [004]
- Fluorocyclization & Fluorofunctionalization: Selectfluor mediates fluorocyclization of alkenes tethered to nucleophiles (alcohols, amides, carboxylic acids) to produce fluorinated tetrahydrofurans, lactones, and lactams. The fluorocarbocation intermediate is captured intramolecularly with excellent diastereoselectivity. [004]
- C-H Fluorination of Unactivated Positions: Selectfluor with photoredox catalysts (Ru(bpy)32+, Ir(ppy)3) enables visible-light-mediated C-H fluorination at unactivated sp3 positions. This late-stage C-H fluorination strategy is revolutionizing medicinal chemistry SAR programs by enabling direct installation of fluorine without de novo synthesis. [005]
- Oxidative Transformations: Selectfluor serves as a mild, metal-free oxidant for: sulfide -> sulfoxide, selenide -> selenoxide, and iodide -> hypervalent iodine(III) species. The selectivity of Selectfluor over other oxidants (mCPBA, Oxone) makes it valuable for substrates with multiple oxidizable functional groups. [005]
Handling and Storage
- GHS Hazard: H317: May cause an allergic skin reaction, H319: Causes serious eye irritation, H334: May cause allergy or asthma symptoms or breathing difficulties if inhaled
- Signal Word: Danger
- Pictograms: GHS05, GHS06, GHS07
- Storage: Store at 2-8 °C or as recommended on the Certificate of Analysis. Keep container tightly closed in a cool, dry, well-ventilated area. Protect from moisture and incompatible materials (strong oxidizing agents, acids, bases). For long-term storage, keep under inert gas (N2 or Ar) if the compound is hygroscopic or oxygen-sensitive. Always consult the supplier's Safety Data Sheet (SDS) for lot-specific storage recommendations and shelf-life information.
- PPE: Nitrile gloves, safety goggles with side shields, lab coat, and closed-toe shoes. Work in a well-ventilated fume hood. Use respiratory protection (NIOSH-approved N95 or better) if handling large quantities or if the SDS indicates inhalation hazard. [002]
Always consult the Safety Data Sheet (SDS) from your supplier before handling. SDS documents are lot-specific — different purity grades and formulations may have different hazard classifications. For bulk handling, consult your institution's chemical hygiene plan and perform a job hazard analysis (JHA) before beginning work. Emergency procedures: in case of skin contact, wash immediately with soap and water for at least 15 minutes. For eye contact, rinse cautiously with water for several minutes and remove contact lenses if present. If inhaled, move to fresh air. Seek medical attention if symptoms persist.
Regulatory & Compliance
Chemical Inventories: Selectfluor (CAS 140681-55-6) is listed on major chemical inventories including the TSCA (Toxic Substances Control Act) inventory in the United States, EINECS (European Inventory of Existing Commercial Chemical Substances) in the EU, and similar inventories in Japan (ENCS), China (IECSC), Korea (KECL), and Australia (AICS). The specific regulatory status of CAS 140681-55-6 should be verified with the appropriate national authority before importing into any jurisdiction, as inventory listing status can change with regulatory updates and new chemical assessments.
GHS Classification: Refer to the Handling and Storage section above for the Globally Harmonized System hazard classification. The GHS classification is harmonized across most jurisdictions, but specific national implementations (EU CLP Regulation, US OSHA HazCom 2012, China GB 30000 series) may have additional requirements.
Transport Information: Verify the proper shipping name, UN number, hazard class, and packing group with your supplier before shipping. Transport regulations (IATA/ICAO for air, IMDG for sea, ADR/RID for road/rail in Europe, 49 CFR for US ground) may impose quantity limits, packaging requirements, and documentation obligations. Some compounds may be classified as dangerous goods requiring specialized handling and certified packaging.
Export Control: Selectfluor is a standard research and industrial chemical. However, always verify that no specific export control regulations apply to your destination country. Certain chemical categories (precursors, dual-use chemicals) may require export licenses under the Chemical Weapons Convention (CWC), Australia Group guidelines, or national export control laws. Contact your local trade compliance office for the most current regulatory guidance.
[004] [002]
Frequently Asked Questions
What is the CAS number of Selectfluor?
The CAS Registry Number is 140681-55-6. Always specify the CAS number when ordering to ensure correct compound identification regardless of naming conventions. [001]
What is the molecular weight of Selectfluor?
The molecular weight is 212.86 g/mol based on the molecular formula C7H14B2ClF2N2. Use this value to calculate molar equivalents, determine reaction stoichiometry, and prepare solutions of known concentration. [001]
What is Selectfluor used for?
Selectfluor is used for: Electrophilic Fluorination of C-H & C=C Bonds (Selectfluor (Banks, 1992) is the most widely used electrophilic fluorinating rea...); Fluorocyclization & Fluorofunctionalization (Selectfluor mediates fluorocyclization of alkenes tethered to nucleophiles (alco...); C-H Fluorination of Unactivated Positions (Selectfluor with photoredox catalysts (Ru(bpy)32+, Ir(ppy)3) enables visible-lig...). For detailed protocols, see the Key Applications section above. [002]
How should Selectfluor be stored?
Store at 2-8 °C or as recommended on the Certificate of Analysis. Keep container tightly closed in a cool, dry, well-ventilated area. Protect from moisture and incompatible materials (strong oxidizing agents, acids, bases). For long-term storage, keep under inert gas (N2 or Ar) if the compound is hygroscopic or oxygen-sensitive. Always consult the supplier's Safety Data Sheet (SDS) for lot-specific storage recommendations and shelf-life information.. Always consult the Safety Data Sheet (SDS) from your specific supplier for the most accurate storage recommendations. [002]
Where can I buy Selectfluor?
Selectfluor (CAS 140681-55-6) may be sourced through CoreyChem. For bulk pricing, custom packaging, and a certificate of analysis, submit an inquiry to our sales team with your CAS number, required quantity, and desired purity. [002]
Where to Buy
Selectfluor (CAS 140681-55-6) is not currently listed in the CoreyChem catalog. Contact [email protected] for sourcing assistance. [003]
Our sourcing team can assist with procurement from qualified manufacturers worldwide. Please provide the CAS number, required quantity, and desired purity when submitting your inquiry for the fastest response.
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References & Sources
https://www.tcichemicals.com/US/en/search/?text=140681-55-6
https://pubchem.ncbi.nlm.nih.gov/compound/140681-55-6
https://pubchem.ncbi.nlm.nih.gov/compound/140681-55-6#section=Use-and-Manufacturing
