Triethyloxonium tetrafluoroborate

Triethyloxonium tetrafluoroborate structural formula

Structural formula

Business number 04H2
Molecular formula C6H15BF4O
Molecular weight 189.99

Meerwein salt

Numbering system

CAS number:368-39-8

MDL number:MFCD00044423

EINECS number:206-705-1

RTECS number:RR4584700

BRN number:3598090

PubChem number:24889377

Physical property data

1. Properties: Colorless and transparent to yellow or light brown liquid

2. Density (g/mL, 25/4℃): 1.33

3. Relative vapor density (g/mL, air=1): Not available

4. Melting point (ºC): 96-97

5. Boiling point (ºC, normal pressure): Not available


6. Boiling point (ºC, 5.2kPa): Not available

7. Refractive index: Not available

8. Flash point (ºC): Not available


9. Specific rotation (º): Not available

10. Autoignition point or ignition temperature (ºC): Not available

11. Vapor pressure (kPa , 25ºC): Not available

12. Saturated vapor pressure (kPa, 60ºC): Not available

13. Heat of combustion (KJ/mol): Not available

14. Critical temperature (ºC): Not available

15. Critical pressure (KPa): Not available

16. Log value of oil-water (octanol/water) partition coefficient : Unavailable

17. Explosion upper limit (%, V/V): Unavailable

18. Explosion lower limit (%, V/V): Unavailable

19. Solubility: Soluble in CH2Cl2.

Toxicological data

Ecological data

This substance may be harmful to the environment, and special attention should be paid to water bodies.

Molecular structure data

None yet

Compute chemical data

1. Reference value for hydrophobic parameter calculation (XlogP): None

2. Number of hydrogen bond donors: 0

3. Number of hydrogen bond acceptors: 5

4. Number of rotatable chemical bonds: 3

5. Number of tautomers: none

6. Topological molecule polar surface area 1

7. Number of heavy atoms: 12

8. Surface charge: 0

9. Complexity: 44.8

10. Number of isotope atoms: 0

11. Determine the number of atomic stereocenters: 0

12. Uncertain number of atomic stereocenters: 0

13. Determine the number of chemical bond stereocenters: 0

14. Number of uncertain chemical bond stereocenters: 0

15. Number of covalent bond units: 2

Properties and stability

It has strong hygroscopicity and should be stored in a solution of ether and methylene chloride at a low temperature of 0~5 oC. Trimethoxyboron tetrafluoride can be stored directly in a drying oven at low temperature. Because it is not hygroscopic, it can be operated and used in the air for a short time.

Storage method

Should be stored at 2-8℃.

Synthesis method

1. Prepared by the reaction of 3-chloro-1,2-epoxypropane and BF3-OEt2 complex.

2. Three-neck the 2 liters Flask, stirrer, liquid funnel and condenser with drying tube��Put it into an oven at 110℃ to dry, install it while hot, and cool it in a dry nitrogen flow. Add 500 ml of sodium-dried ether and 284 g (252 ml, 2.00 mol) of freshly distilled boron trifluoride ether solution into the flask. Add 140 grams (119 ml, 1.51 mol) of 3-chloropropylene oxide dropwise into the stirring liquid at a rate that maintains vigorous boiling (it takes about 1 hour). After the addition is complete, reflux for 1 hour and leave at room temperature overnight. Replace the stirrer with a suction filter. Aspirate the clear ether above the triethyloxytetrafluoroborate crystals. These operations need to be carried out under nitrogen protection to avoid humid air entering the flask. The crystals were washed with three 500 ml portions of sodium-dried ether. Place the flask into a drying oven. The product is collected in a glass core funnel under nitrogen protection and bottled. Triethyloxytetrafluoroborate is a colorless crystal.


1. Powerful ethylating agent, acid esterification, protein carboxyl modification.

2. Ethylation reagents of oxygen, nitrogen, and sulfur in ethers, thioethers, nitriles, ketones, esters, and amides react with alcohol to form ether. O-ethylation of enol hydroxypyridine. With nitrile generates ethyl secondary amine. Esterify and split thioacetals. Remove N-benzoyl and N-acetyl groups. Reduction of secondary and tertiary amides to equivalent secondary and tertiary amines. Preparation of thiolactone from lactone. Preparation of beta-keto acid ester from ketone azoacetate. Preparation of L-proline.

3.Meerwein salt is a very effective alkyl reagent, which can act on the alkylation reaction of many relatively inert weak nucleophilic functional groups.

Thioethers can be converted into the corresponding sulfonium salts under the action of trimethoxyboron tetrafluoride, thus showing better functional group leaving ability and triggering a series of reactions (Formula 2)[1].

Amide substrate Both O-alkylation and S-alkylation of sulfamide substrates can react well under the action of Meerwein salt, and the generated imine ester has higher reaction Activity, such as in the total synthesis of indolizomycin, the generated imide ester is reduced by sodium borohydride to obtain a nine-membered ring natural product (formula 3)[2].

Meerwein salt energy in aqueous phase Acts on carboxylic acid to achieve esterification reaction (Formula 4)[3]. Under these reaction conditions, the amide group does not undergoO-alkylation. In the absence of aprotic solvents and bases, carboxylic acid amide compounds will only undergo an O-alkylation reaction (Formula 5)[4].

An important preparation of Fisher carbene The method of complexing is to utilize the alkylation ability of triethoxyboron tetrafluoride. With the action of appropriate nucleophiles such as alkyllithium or aryllithium, Fisher’s reagent can be synthesized in one step, and then other reactions can be realized (Formula 6)[5].

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