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Burgess Reagent Synthesis is usually done in these steps: First, chlorosulfonyl isocyanate (ClSO₂NCO) is reacted with anhydrous methanol at low temperatures (-78°C to 0°C) in anhydrous diethyl ether or dichloromethane to produce methyl chlorosulfonyl carbamate (ClSO₂NHCOOCH₃). This step requires strict control of moisture content; Next, triethylamine is added dropwise to the reaction system under an inert atmosphere, reacting with the intermediate to form a crystalline solid. The temperature must be maintained below 0°C to prevent side reactions; After the reaction is complete, the triethylamine hydrochloride salt is removed by filtration, and the filtrate is concentrated under reduced pressure to obtain a white to off-white solid crude product. Finally, high-purity Burgess reagent is obtained through recrystallization (commonly using a mixture of anhydrous ether and pentane as the solvent) or column chromatography purification. The entire synthesis process must be strictly protected from moisture, as this reagent is extremely sensitive to water. The yield typically ranges between 60–80%. Its structure can be characterized by ¹H NMR (δ 1.2–1.4 ppm for multiple peaks of triethylmethyl, δ 3.7 ppm for a single peak of methoxy) and IR (strong carbonyl absorption peak near 1720 cm⁻¹). This reagent is widely used as a strong dehydrating agent in organic transformation reactions such as the dehydration of alcohols to alkenes and the dehydration of amides to nitriles.
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Chemical Formula |
C8H18N2O4S |
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Exact Mass |
238 |
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Molecular Weight |
238 |
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m/z |
238 (100.0%), 239 (8.7%), 240 (4.5%) |
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Elemental Analysis |
C, 40.32; H, 7.61; N, 11.76; O, 26.85; S, 13.45 |
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Melting point 76-79 ° C (lit.), Density 1.3023 (rough estimate), Refractive index 1.6300 (estimated), Storage conditions - 20 ° C, Solubility in organic solvents, Morphology crystal powder, Color slightly yellow, Sensitivity, BRN 1432131, InChIKeyYSHOWEKUVWPFNR-UHFFFAOYSA-N, Hazard symbol (GHS), GHS07, Warning word, Hazard description h315-h319-h335, Precautions p264-p280-p302 + p352 + p332 + P313 + p362 + p364-p305 + P351 + P338 + P337 + p313-p261-p305 + P351 + p338-p280a-p304 + p340-p405-p501a, Dangerous goods sign Xi, Hazard category code 36 / 37 / 38, Safety instructions 26-36-37 / 39, WGK Germany 3, F 10-21, TSCA No
Synthesis Method of Burgess Reagent
Burgess Reagent (chemical name: N-(Triethylammonium Sulfon酰) Aminomethanoic Acid Methyl Ester, or Methyl Ester of Methoxycarbonyl Sulfonamide Triethylammonium Inner Salt) is a mild and highly efficient neutral dehydrating agent. Its synthesis process must strictly follow an anhydrous condition to avoid the decomposition of the reagent. The following are the core synthesis steps and key details：
Raw material preparation
The main raw materials include chlorosulfonated isocyanate (ClSO₂NCO), methanol (MeOH), and triethylamine (Et₃N). All solvents (such as benzene and toluene) need to be treated with anhydrous substances (such as molecular sieve drying or sodium wire reflux), and the reaction vessel needs to be thoroughly dried and filled with an inert gas (such as nitrogen) for protection.
The first reaction: Esterification of chlorosulfonated isocyanate and methanol
At a low temperature (0-5°C), slowly add chlorosulfonated isocyanate to anhydrous methanol dropwise to form the intermediate methoxycarbonyl sulfonyl chloride (MeOCOSO₂Cl). This step requires strict control of the addition rate to avoid local overheating and cause side reactions. After the reaction is completed, remove the unreacted methanol by vacuum distillation to obtain the purified intermediate.
The second reaction: Quaternization of the intermediate with triethylamine
Dissolve the intermediate methoxycarbonyl sulfonyl chloride in anhydrous benzene and add triethylamine dropwise under an ice bath. The reaction immediately generates a white precipitate (Burgess Reagent) and releases hydrogen chloride (HCl). Collect the precipitate by filtration and wash it multiple times with cold benzene to remove unreacted triethylamine and by-products. Finally, dry the product at low temperature under vacuum to obtain high-purity Burgess Reagent (melting point 71-72°C).
Storage conditions
The Burgess Reagent is extremely sensitive to air and moisture and should be stored in an inert gas environment below -20℃ to prevent decomposition and loss.
Core Usage of Burgess Reagent
The main application of Burgess Reagent Synthesis is as a dehydrating agent. It promotes the dehydration reactions of functional groups such as alcohols and amides under mild conditions (from low temperature to room temperature), and is particularly suitable for substrates that are sensitive to acids or bases. The following are its typical application scenarios and operational points:
Alcohol dehydration to form alkenes
The Burgess Reagent can efficiently catalyze the cis-dehydration of secondary alcohols, generating double bonds. For example, when synthesizing macrolide compounds, treating β-hydroxy carbonyl compounds with the Burgess Reagent can selectively generate cis-alkenes, avoiding the loss of stereoselectivity caused by traditional methods (such as acid catalysis). During the operation, the substrate is dissolved in anhydrous dichloromethane (DCM), 1.0-1.5 equivalents of the Burgess Reagent are added, and the reaction is stirred at room temperature for several hours to overnight. After the reaction is completed, the product is purified by a silica gel column.
Hydroxyl amide cyclization and dehydration to form oxazoles
For hydroxyl amides (such as derivatives of serine or threonine), the Burgess Reagent can promote intramolecular cyclization, generating 4,5-dihydroxazoles (2-oxazoline). For example, when synthesizing intermediate compounds of antimalarial drugs, treating hydroxyl amides with the Burgess Reagent can efficiently construct the oxazole skeleton. The reaction conditions are similar to those of secondary alcohol dehydration, but the reaction time needs to be controlled to avoid the formation of pyridine-type by-products due to excessive dehydration.
Amine dehydration to form nitriles
The Burgess Reagent can also be used for the dehydration of primary amines to generate nitrile compounds. For example, when synthesizing glutamine derivatives, treating the amine with the Burgess Reagent can selectively generate the nitrile group while retaining other sensitive functional groups (such as ester groups or halogens) within the molecule. This reaction needs to be carried out at a low temperature (0-5°C) to reduce side reactions.
Non-dehydration reaction applications
Recent studies have shown that the Burgess Reagent can also be used in non-dehydration reactions, such as the synthesis of sulfonyl amide esters from 1,2-diol or epoxy alcohols, the synthesis of α- and β-glycosylamines from carbohydrates, and the synthesis of cyclic sulfonamides from 1,2-aminoliques. These reactions utilize the unique reactivity of the Burgess Reagent, expanding its application scope in organic synthesis.
Operating Precautions and Advantages
Anhydrous condition
The Burgess Reagent is extremely sensitive to moisture. All solvents and instruments need to be thoroughly dried, and the reaction should be carried out under inert gas protection.
Mild conditions
Compared with traditional dehydration methods (such as acid catalysis or high-temperature heating), the Burgess Reagent can complete the reaction at low temperatures to room temperature, avoiding substrate decomposition or loss of stereoselectivity.
Stereoselectivity
The dehydration reactions catalyzed by the Burgess Reagent usually have high stereoselectivity, especially suitable for the synthesis of complex molecules.
Post-treatment is simple
After the reaction is completed, the by-products of the Burgess Reagent (such as triethylamine hydrochloride) are easily soluble in water and can be removed through simple extraction or filtration, simplifying the post-treatment steps.
Burgess Reagent Synthesis is a mild and selective dehydrating agent widely used in organic synthesis, especially suitable for the dehydration reaction of alcohols to produce alkenes. Its manufacturing process requires strict adherence to anhydrous conditions to ensure the stability and activity of the reagent. The following is the detailed manufacturing information of Burgess Reagent：
Raw Material Preparation
The main raw materials required for manufacturing Burgess Reagent are as follows:
Chlorosulfonyl isocyanate (ClSO₂NCO)
As the key starting material for the reaction, its purity and anhydrous state must be ensured.
Anhydrous methanol (MeOH)
As the reagent for the esterification reaction, it needs to be treated as anhydrous, such as by molecular sieve drying or sodium wire reflux.
Anhydrous benzene
As the solvent, it must be thoroughly dried to avoid the influence of moisture on the reaction.
Triethylamine (Et₃N)
As the quaternary ammonium reagent, it also needs to be anhydrous.
Manufacturing Steps
Esterification Reaction
At a low temperature (0-15℃), slowly add anhydrous methanol to the mixture of chlorosulfonyl isocyanate and anhydrous benzene. This step requires strict control of the addition speed and reaction temperature to avoid local overheating and resulting side reactions.
After completion, stir at room temperature for several hours to allow the esterification reaction to proceed fully, generating the intermediate methoxycarbonyl sulfonyl chloride (MeOCOSO₂Cl).
Intermediate Purification
After the reaction is complete, remove the unreacted methanol and benzene by vacuum distillation to obtain the purified methoxycarbonyl sulfonyl chloride intermediate. This step requires ensuring the mildness of the distillation conditions to avoid the decomposition of the intermediate.
Quaternary Ammonium Formation Reaction
Dissolve the methoxycarbonyl sulfonyl chloride in anhydrous benzene, and add triethylamine dropwise at a low temperature (0-15℃). Immediately, a white precipitate (Burgess Reagent) forms, releasing hydrogen chloride (HCl).
This step requires strict control of the addition speed and reaction temperature to ensure the smooth progress of the quaternary ammonium formation reaction. After completion, stir at room temperature for several hours to ensure complete reaction.
Product Collection and Purification
After the reaction is complete, collect the precipitate by filtration and wash it multiple times with cold benzene to remove unreacted triethylamine and by-products.
Concentrate the filtrate and dissolve it in anhydrous tetrahydrofuran (THF) for recrystallization to further improve the purity of the product.
Finally, dry the product at low temperature under vacuum to obtain high-purity Burgess Reagent.
Precautions in the Manufacturing Process
Anhydrous Condition
Burgess Reagent is extremely sensitive to moisture. All raw materials and solvents need to be thoroughly dried, and the reaction vessel needs to be dried and filled with inert gas for protection.
Temperature Control
Both the esterification reaction and the quaternary ammonium formation reaction need to be carried out at low temperatures to avoid side reactions and reagent decomposition.
Addition Speed
In the esterification reaction and quaternary ammonium formation reaction, strict control of the addition speed is required to ensure the uniformity and controllability of the reaction.
Product Storage
Burgess Reagent should be stored sealed in an inert gas environment at a low temperature (below -20℃) to avoid decomposition and loss.
Application and Expansion of Manufacturing Information
The manufacturing information of Burgess Reagent Synthesis not only provides an important dehydration agent for organic synthesis, but also expands its application in other fields. For example, Burgess Reagent can be used to synthesize sulfonamide esters from 1,2-diol or epoxy alcohol, synthesize α- and β-glycosylamines from carbohydrates, and synthesize cyclic sulfonamides from 1,2-aminoliques. These applications utilize the unique reaction activity of Burgess Reagent, providing new strategies for the synthesis of complex molecules.
FAQ
1. What is the Burgess reagent?
It is a mild and efficient internal dehydrating agent, with the chemical name methyl chloroformylaminoformate methyl ester. It is used to selectively dehydrate alcohols, 1,2-diol and amides into alkenes, ethylene oxide and nitriles respectively.
2. What are the key synthesis steps of it?
The classical synthetic pathway mainly consists of two steps: Firstly, methyl chloroformate reacts with triethylamine to form the intermediate methyl chloroformate ammonium salt; subsequently, this intermediate reacts with methyl carbamyl formate at low temperature, and finally, a white solid product crystallizes out.
3. What are the most important precautions to take during synthesis and usage?
The key point is to conduct the operation strictly without water. This reagent is extremely sensitive to moisture and is prone to hydrolysis and loss of effectiveness. All reactions must be carried out under the protection of an inert gas (such as nitrogen or argon), using anhydrous solvents and dry glassware.
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