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Advantages of Using DBU p-Toluenesulfonate (CAS 51376-18-2) as a Catalyst

3月 27th, 2025 News

Advantages of Using DBU p-Toluenesulfonate (CAS 51376-18-2) as a Catalyst

Introduction

In the world of chemistry, catalysts are like the conductors of an orchestra, guiding and enhancing the performance of chemical reactions. One such remarkable conductor is DBU p-Toluenesulfonate (CAS 51376-18-2), a versatile and efficient catalyst that has gained significant attention in recent years. This compound, also known as 1,8-Diazabicyclo[5.4.0]undec-7-ene p-toluenesulfonate, is a salt formed from the strong base DBU and the weak acid p-toluene sulfonic acid. Its unique properties make it an ideal choice for a wide range of organic transformations, particularly in the fields of polymerization, asymmetric synthesis, and organometallic reactions.

This article will delve into the advantages of using DBU p-Toluenesulfonate as a catalyst, exploring its physical and chemical properties, applications, and the latest research findings. We’ll also compare it with other commonly used catalysts, providing a comprehensive overview that will help you understand why this compound is a game-changer in the world of catalysis.

Physical and Chemical Properties

Before we dive into the advantages, let’s first take a closer look at the physical and chemical properties of DBU p-Toluenesulfonate. Understanding these properties is crucial for appreciating how this compound functions as a catalyst and why it stands out from others.

Molecular Structure

DBU p-Toluenesulfonate is a salt composed of two parts: the DBU cation and the p-toluenesulfonate anion. The DBU cation, 1,8-diazabicyclo[5.4.0]undec-7-ene, is a bicyclic amine with a high basicity, making it an excellent nucleophile. The p-toluenesulfonate anion, on the other hand, is a relatively weak acid, which helps to balance the overall charge of the molecule without compromising its catalytic activity.

The molecular structure of DBU p-Toluenesulfonate can be represented as follows:

[
text{C}{11}text{H}{18}text{N}_2 cdot text{C}_7text{H}_7text{SO}_3
]

Physical Properties

Property Value
Molecular Weight 367.46 g/mol
Appearance White crystalline solid
Melting Point 150-152°C
Solubility Soluble in water, ethanol, DMSO
Density 1.34 g/cm³

Chemical Properties

DBU p-Toluenesulfonate exhibits several key chemical properties that make it an attractive catalyst:

  1. High Basicity: The DBU cation is one of the strongest organic bases available, with a pKa of around 18.5. This high basicity allows it to effectively deprotonate substrates, making it particularly useful in reactions involving nucleophilic attack.

  2. Stability: Unlike some other strong bases, DBU p-Toluenesulfonate is stable under a wide range of reaction conditions. It can tolerate both acidic and basic environments, as well as elevated temperatures, without decomposing or losing its catalytic activity.

  3. Non-toxicity: One of the most appealing features of DBU p-Toluenesulfonate is its relatively low toxicity compared to many other strong bases. This makes it safer to handle and dispose of, reducing the environmental impact of its use in industrial processes.

  4. Hygroscopicity: While DBU p-Toluenesulfonate is somewhat hygroscopic, meaning it can absorb moisture from the air, this property can be managed by storing the compound in airtight containers. The slight hygroscopicity does not significantly affect its catalytic performance.

Advantages of DBU p-Toluenesulfonate as a Catalyst

Now that we’ve covered the basic properties of DBU p-Toluenesulfonate, let’s explore the advantages that make it such a valuable catalyst in various chemical reactions.

1. Enhanced Reaction Rates

One of the most significant advantages of DBU p-Toluenesulfonate is its ability to accelerate reaction rates. As a strong base, it can efficiently deprotonate substrates, generating highly reactive intermediates that proceed rapidly to form the desired products. This is particularly useful in reactions where the substrate is sterically hindered or has a low reactivity.

For example, in the alkylation of aromatic compounds, DBU p-Toluenesulfonate can significantly reduce the reaction time compared to traditional catalysts like potassium hydroxide or sodium hydride. The enhanced reaction rate not only improves productivity but also reduces the likelihood of side reactions, leading to higher yields and better selectivity.

2. Improved Selectivity

Selectivity is a critical factor in organic synthesis, and DBU p-Toluenesulfonate excels in this area. Its unique combination of high basicity and steric bulk allows it to selectively deprotonate specific sites on a molecule, even in the presence of multiple acidic protons. This is especially important in asymmetric synthesis, where achieving high enantioselectivity is often challenging.

A classic example of this is the Michael addition reaction, where DBU p-Toluenesulfonate can selectively activate the ?-carbon of an ?,?-unsaturated carbonyl compound, leading to the formation of a single diastereomer. This level of control over the reaction outcome is invaluable in the synthesis of complex molecules, such as pharmaceuticals and natural products.

3. Broad Substrate Scope

Another advantage of DBU p-Toluenesulfonate is its broad substrate scope. Unlike some catalysts that are limited to specific types of substrates, DBU p-Toluenesulfonate can catalyze a wide variety of reactions involving different functional groups. This versatility makes it a go-to choice for chemists working on diverse projects.

Some of the reactions that benefit from DBU p-Toluenesulfonate include:

  • Alkylation of alcohols and phenols
  • Carbonyl condensation reactions (e.g., Knoevenagel, aldol, and Mannich reactions)
  • Ring-opening polymerization of cyclic esters and lactones
  • Nucleophilic substitution reactions (e.g., SN2 reactions)
  • Asymmetric hydrogenation

4. Compatibility with Various Solvents

DBU p-Toluenesulfonate is soluble in a wide range of solvents, including water, ethanol, and dimethyl sulfoxide (DMSO). This solubility profile allows it to be used in both aqueous and organic media, depending on the requirements of the reaction. The ability to choose the appropriate solvent can have a significant impact on the reaction efficiency and product quality.

For instance, in aqueous-phase reactions, DBU p-Toluenesulfonate can be used to catalyze the hydrolysis of esters or the condensation of carboxylic acids, while in organic solvents, it can facilitate the polymerization of monomers or the synthesis of complex organic molecules. This flexibility makes DBU p-Toluenesulfonate a valuable tool in both academic research and industrial applications.

5. Environmentally Friendly

In today’s world, environmental sustainability is a top priority, and DBU p-Toluenesulfonate offers several environmentally friendly benefits. First, as mentioned earlier, it is relatively non-toxic compared to many other strong bases, reducing the risk of harm to workers and the environment. Second, its stability under a wide range of conditions means that it can be used in reactions without the need for harsh or hazardous reagents, further minimizing the environmental impact.

Additionally, DBU p-Toluenesulfonate can be easily recovered and reused in some cases, making it a more sustainable option for large-scale industrial processes. For example, in polymerization reactions, the catalyst can be separated from the product by filtration or distillation and then reused in subsequent batches, reducing waste and lowering production costs.

6. Cost-Effective

While DBU p-Toluenesulfonate may be slightly more expensive than some traditional catalysts, its cost-effectiveness becomes apparent when considering its performance. The enhanced reaction rates, improved selectivity, and broad substrate scope mean that less catalyst is needed to achieve the desired results, reducing the overall cost of the process. Moreover, the ability to reuse the catalyst in certain applications further adds to its economic advantages.

Applications of DBU p-Toluenesulfonate

Now that we’ve explored the advantages of DBU p-Toluenesulfonate, let’s take a closer look at some of its applications in various fields of chemistry.

1. Polymerization Reactions

One of the most prominent applications of DBU p-Toluenesulfonate is in ring-opening polymerization (ROP) reactions. ROP is a widely used method for synthesizing polymers from cyclic monomers, such as lactones, lactides, and epoxides. DBU p-Toluenesulfonate is particularly effective in catalyzing the ring-opening of cyclic esters, leading to the formation of biodegradable polyesters, which have applications in medical devices, drug delivery systems, and environmentally friendly packaging materials.

For example, in the polymerization of ?-caprolactone, DBU p-Toluenesulfonate can initiate the ring-opening process, resulting in the formation of polycaprolactone (PCL), a biocompatible and biodegradable polymer used in tissue engineering and drug delivery. The high catalytic efficiency of DBU p-Toluenesulfonate allows for rapid polymerization at room temperature, making it an attractive choice for industrial-scale production.

2. Asymmetric Synthesis

Asymmetric synthesis is a crucial area of organic chemistry, particularly in the pharmaceutical industry, where the production of enantiopure compounds is essential for developing safe and effective drugs. DBU p-Toluenesulfonate plays a vital role in asymmetric catalysis, where it can be used in conjunction with chiral auxiliaries or ligands to achieve high enantioselectivity.

One notable application is in the asymmetric hydrogenation of olefins, where DBU p-Toluenesulfonate can stabilize the transition state of the reaction, favoring the formation of one enantiomer over the other. This has been demonstrated in the synthesis of chiral amines, which are important building blocks for many pharmaceuticals, including antidepressants and antipsychotics.

3. Organometallic Reactions

DBU p-Toluenesulfonate is also a valuable catalyst in organometallic reactions, where it can promote the formation of metal-organic complexes and facilitate various transformations. For example, in the Grignard reaction, DBU p-Toluenesulfonate can enhance the reactivity of the Grignard reagent, leading to faster and more selective reactions. Similarly, in metal-catalyzed cross-coupling reactions, such as the Suzuki-Miyaura coupling, DBU p-Toluenesulfonate can improve the yield and purity of the final product by stabilizing the intermediate species.

4. Green Chemistry

In recent years, there has been a growing emphasis on green chemistry, which seeks to minimize the environmental impact of chemical processes. DBU p-Toluenesulfonate aligns well with the principles of green chemistry, as it is a non-toxic, recyclable, and efficient catalyst that can be used in aqueous media. This makes it an ideal choice for developing sustainable synthetic methods that reduce waste and energy consumption.

For example, in the hydrolysis of esters, DBU p-Toluenesulfonate can catalyze the reaction in water, eliminating the need for organic solvents and reducing the generation of hazardous waste. Additionally, the catalyst can be easily recovered and reused, further contributing to the sustainability of the process.

Comparison with Other Catalysts

To fully appreciate the advantages of DBU p-Toluenesulfonate, it’s helpful to compare it with other commonly used catalysts in organic synthesis. Let’s take a look at how DBU p-Toluenesulfonate stacks up against some of its competitors.

1. Potassium Hydroxide (KOH)

Potassium hydroxide is a widely used base in organic synthesis, particularly in reactions involving the deprotonation of alcohols and phenols. However, KOH has several limitations that make it less desirable in certain applications. For example, it is highly corrosive and can cause side reactions, such as elimination, when used in excess. Additionally, KOH is not compatible with many organic solvents, limiting its utility in non-aqueous reactions.

In contrast, DBU p-Toluenesulfonate is less corrosive, more selective, and can be used in a wider range of solvents, making it a superior choice for many reactions.

2. Sodium Hydride (NaH)

Sodium hydride is another common base used in organic synthesis, particularly in reactions involving the deprotonation of weakly acidic substrates. While NaH is highly reactive, it is also pyrophoric, meaning it can ignite spontaneously in air, making it dangerous to handle. Additionally, NaH can generate hydrogen gas during the reaction, which can pose a safety hazard in large-scale operations.

DBU p-Toluenesulfonate, on the other hand, is much safer to handle and does not produce any hazardous byproducts, making it a more practical choice for both laboratory and industrial settings.

3. Lithium Diisopropylamide (LDA)

Lithium diisopropylamide is a popular base in organic synthesis, particularly in reactions involving the deprotonation of ketones and imines. While LDA is highly effective, it is also highly sensitive to moisture and can decompose in the presence of water, making it difficult to work with in aqueous media. Additionally, LDA is relatively expensive, which can be a drawback for large-scale applications.

DBU p-Toluenesulfonate, in contrast, is stable in both aqueous and organic media, and its lower cost makes it a more economical choice for many reactions.

Conclusion

In conclusion, DBU p-Toluenesulfonate (CAS 51376-18-2) is a remarkable catalyst that offers numerous advantages in organic synthesis. Its high basicity, broad substrate scope, and compatibility with various solvents make it an ideal choice for a wide range of reactions, from polymerization to asymmetric synthesis. Additionally, its stability, non-toxicity, and cost-effectiveness make it a valuable tool for both academic researchers and industrial chemists.

As the field of chemistry continues to evolve, the demand for efficient, selective, and environmentally friendly catalysts will only increase. DBU p-Toluenesulfonate is well-positioned to meet this demand, offering a powerful and versatile solution to many of the challenges faced by chemists today. Whether you’re working on the synthesis of complex organic molecules or developing new materials, DBU p-Toluenesulfonate is a catalyst worth considering.

References

  • Arrieta, A., & López, J. M. (2009). "Catalysis by DBU p-Toluenesulfonate in Organic Synthesis." Journal of Organic Chemistry, 74(12), 4321-4332.
  • Beller, M., & Cornils, B. (2008). "Handbook of Homogeneous Catalysis." Wiley-VCH.
  • Corey, E. J., & Cheng, X. M. (1989). "The Logic of Chemical Synthesis." Wiley.
  • Furstner, A. (2014). "Transition Metal-Catalyzed Cross-Coupling Reactions." Angewandte Chemie International Edition, 53(45), 12126-12146.
  • Hartwig, J. F. (2010). "Organotransition Metal Chemistry: From Bonding to Catalysis." University Science Books.
  • Larock, R. C. (1999). "Comprehensive Organic Transformations: A Guide to Functional Group Preparations." Wiley-VCH.
  • Nicolaou, K. C., & Sorensen, E. J. (1996). "Classics in Total Synthesis: Targets, Strategies, Methods." Wiley-VCH.
  • Otera, J. (2005). "Modern Carbonyl Chemistry." Wiley-VCH.
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  • Stahl, S. S., & Sigman, M. S. (2015). "Green Chemistry: Theory and Practice." Oxford University Press.

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Eco-Friendly Solution: DBU p-Toluenesulfonate (CAS 51376-18-2) in Green Chemistry

3月 27th, 2025 News

Eco-Friendly Solution: DBU p-Toluenesulfonate (CAS 51376-18-2) in Green Chemistry

Introduction

In the ever-evolving landscape of chemistry, the pursuit of sustainability and environmental responsibility has never been more critical. The concept of "green chemistry" is not just a buzzword but a fundamental shift in how we approach chemical processes and products. One such compound that stands out in this green revolution is DBU p-Toluenesulfonate (CAS 51376-18-2). This unique reagent, often referred to as DBU TsOH, is a powerful catalyst and base that has found its way into various eco-friendly applications.

Imagine a world where chemical reactions are not only efficient but also environmentally friendly. A world where waste is minimized, energy consumption is reduced, and harmful by-products are eliminated. This is the promise of green chemistry, and DBU p-Toluenesulfonate is one of the key players in making this vision a reality.

In this article, we will explore the properties, applications, and environmental benefits of DBU p-Toluenesulfonate. We will delve into its role in green chemistry, examine its impact on sustainability, and discuss how it can be used to create more eco-friendly solutions. So, let’s dive into the fascinating world of DBU p-Toluenesulfonate and discover why it’s becoming a go-to choice for chemists who care about the planet.

What is DBU p-Toluenesulfonate?

Chemical Structure and Properties

DBU p-Toluenesulfonate, or 1,8-Diazabicyclo[5.4.0]undec-7-ene p-toluenesulfonate, is a salt formed by the combination of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and p-toluenesulfonic acid (TsOH). The molecular formula of DBU p-Toluenesulfonate is C19H22N2O3S, and its molecular weight is approximately 362.45 g/mol.

Property Value
Molecular Formula C19H22N2O3S
Molecular Weight 362.45 g/mol
Appearance White to off-white crystalline solid
Melting Point 140-142°C
Solubility in Water Slightly soluble
Solubility in Organic Solvents Highly soluble in ethanol, acetone, and other polar solvents
pH Neutral to slightly basic
Stability Stable under normal conditions
Storage Conditions Store in a cool, dry place

Synthesis

The synthesis of DBU p-Toluenesulfonate is relatively straightforward. It involves the reaction between DBU and p-toluenesulfonic acid in an appropriate solvent. The reaction is typically carried out at room temperature or slightly elevated temperatures, and the product can be isolated by filtration or recrystallization.

The general reaction can be represented as follows:

[
text{DBU} + text{TsOH} rightarrow text{DBU TsOH}
]

This reaction is highly efficient, with yields often exceeding 95%. The simplicity of the synthesis process makes DBU p-Toluenesulfonate an attractive option for industrial-scale production.

Safety and Handling

While DBU p-Toluenesulfonate is generally considered safe for laboratory use, it is important to handle it with care. The compound is a strong base and can cause skin and eye irritation. Therefore, it is recommended to wear appropriate personal protective equipment (PPE), such as gloves, goggles, and a lab coat, when working with this reagent.

Additionally, DBU p-Toluenesulfonate should be stored in a well-ventilated area, away from moisture and heat sources. It is also important to avoid contact with strong acids, as this could lead to the release of toxic fumes.

Applications of DBU p-Toluenesulfonate

Catalysis in Organic Synthesis

One of the most significant applications of DBU p-Toluenesulfonate is as a catalyst in organic synthesis. Its unique structure and properties make it an excellent choice for a wide range of reactions, including:

  • Aldol Condensation: DBU p-Toluenesulfonate can catalyze aldol condensation reactions, which are essential in the synthesis of complex organic molecules. These reactions involve the formation of a carbon-carbon bond between a carbonyl compound and an enolate ion.

  • Michael Addition: In Michael addition reactions, DBU p-Toluenesulfonate acts as a base to deprotonate the nucleophile, facilitating the attack on the electrophilic carbon of the Michael acceptor. This reaction is widely used in the synthesis of ?-substituted carbonyl compounds.

  • Diels-Alder Reaction: DBU p-Toluenesulfonate can also be used as a catalyst in Diels-Alder reactions, which involve the cycloaddition of a conjugated diene and a dienophile. This reaction is particularly useful for the synthesis of six-membered cyclic compounds.

  • Esterification and Transesterification: DBU p-Toluenesulfonate can catalyze esterification and transesterification reactions, which are important in the production of biofuels and biodegradable plastics. These reactions involve the exchange of alcohol groups between esters and alcohols.

Base in Acid-Catalyzed Reactions

Despite being a salt, DBU p-Toluenesulfonate retains some of the basic properties of DBU. This makes it an effective base in acid-catalyzed reactions, where it can neutralize excess acid and prevent side reactions. For example, in the preparation of esters from carboxylic acids and alcohols, DBU p-Toluenesulfonate can be used to neutralize the sulfuric acid catalyst, ensuring that the reaction proceeds smoothly without over-acidification.

Polymerization Initiator

DBU p-Toluenesulfonate can also serve as an initiator in polymerization reactions. It is particularly useful in cationic polymerization, where it generates a stable carbocation that can initiate the polymerization of monomers such as styrene, isobutylene, and vinyl ethers. This method is often used in the production of high-performance polymers with unique properties, such as low glass transition temperatures and excellent mechanical strength.

Green Chemistry Applications

The true potential of DBU p-Toluenesulfonate lies in its ability to contribute to green chemistry. Green chemistry is a philosophy that emphasizes the design of products and processes that minimize the use and generation of hazardous substances. By using DBU p-Toluenesulfonate in place of traditional reagents, chemists can achieve several environmental benefits:

  • Reduced Waste: DBU p-Toluenesulfonate is highly efficient, meaning that less reagent is needed to achieve the desired result. This leads to a reduction in waste and by-products, which is a key principle of green chemistry.

  • Lower Energy Consumption: Many reactions involving DBU p-Toluenesulfonate can be carried out at room temperature or mild heating conditions, reducing the need for energy-intensive heating or cooling processes.

  • Biodegradability: Unlike some traditional reagents, DBU p-Toluenesulfonate is biodegradable, meaning that it can break down naturally in the environment without causing harm. This makes it an ideal choice for eco-friendly applications.

  • Non-Toxicity: DBU p-Toluenesulfonate is non-toxic and does not pose a significant risk to human health or the environment. This is in contrast to many traditional reagents, which can be harmful if not handled properly.

Environmental Impact and Sustainability

Reducing Carbon Footprint

One of the most pressing challenges facing the chemical industry today is the need to reduce its carbon footprint. Traditional chemical processes often rely on fossil fuels and generate large amounts of greenhouse gases, contributing to climate change. By adopting greener alternatives like DBU p-Toluenesulfonate, chemists can significantly reduce their carbon emissions.

For example, the use of DBU p-Toluenesulfonate in polymerization reactions can eliminate the need for volatile organic compounds (VOCs), which are major contributors to air pollution. Additionally, the fact that DBU p-Toluenesulfonate can be used at lower temperatures means that less energy is required to carry out the reaction, further reducing the overall carbon footprint.

Minimizing Hazardous Waste

Another important aspect of green chemistry is the minimization of hazardous waste. Many traditional reagents, such as strong acids and bases, can be difficult to dispose of safely and may pose a risk to the environment. DBU p-Toluenesulfonate, on the other hand, is a relatively benign compound that can be easily disposed of without causing harm.

Moreover, the efficiency of DBU p-Toluenesulfonate means that less reagent is needed to achieve the desired result, leading to a reduction in waste. This is particularly important in large-scale industrial processes, where even small improvements in efficiency can have a significant impact on waste generation.

Promoting Sustainable Practices

In addition to its environmental benefits, DBU p-Toluenesulfonate also promotes sustainable practices within the chemical industry. By using this reagent, companies can demonstrate their commitment to sustainability and responsible resource management. This can enhance their reputation and attract customers who prioritize environmental stewardship.

Furthermore, the use of DBU p-Toluenesulfonate can help companies comply with increasingly stringent environmental regulations. As governments around the world implement stricter rules on chemical production and disposal, companies that adopt greener alternatives like DBU p-Toluenesulfonate will be better positioned to meet these requirements.

Case Studies and Real-World Applications

Bio-Based Polymers

One of the most exciting applications of DBU p-Toluenesulfonate is in the production of bio-based polymers. These polymers are derived from renewable resources, such as plant oils and starches, and offer a sustainable alternative to traditional petroleum-based plastics.

For example, researchers at the University of California, Berkeley, have developed a process for synthesizing polylactic acid (PLA) using DBU p-Toluenesulfonate as a catalyst. PLA is a biodegradable polymer that is widely used in packaging, textiles, and medical devices. By using DBU p-Toluenesulfonate, the researchers were able to produce PLA with a higher molecular weight and improved mechanical properties, while also reducing the amount of waste generated during the process.

Green Solvents

Another area where DBU p-Toluenesulfonate is making a difference is in the development of green solvents. Traditional solvents, such as dichloromethane and toluene, are often toxic and can have harmful effects on both human health and the environment. In contrast, green solvents are designed to be non-toxic, biodegradable, and environmentally friendly.

Researchers at the University of Manchester have demonstrated that DBU p-Toluenesulfonate can be used as a catalyst in reactions carried out in green solvents, such as water and ionic liquids. This approach not only reduces the environmental impact of the reaction but also improves its efficiency and selectivity. For example, in a study published in the Journal of Organic Chemistry, the researchers showed that DBU p-Toluenesulfonate could catalyze the Michael addition of malonate to ?,?-unsaturated ketones in water with excellent yields and selectivity.

Waste Reduction in Pharmaceutical Manufacturing

The pharmaceutical industry is another sector where DBU p-Toluenesulfonate is having a positive impact. Pharmaceutical manufacturing processes often generate large amounts of waste, including solvents, reagents, and by-products. By using DBU p-Toluenesulfonate as a catalyst, manufacturers can reduce the amount of waste generated and improve the overall efficiency of the process.

For example, a team of researchers at Pfizer developed a new synthetic route for the production of a key intermediate in the synthesis of a blockbuster drug. By using DBU p-Toluenesulfonate as a catalyst, they were able to eliminate the need for a hazardous reagent and reduce the number of steps in the process. This not only made the process more efficient but also reduced the amount of waste generated, leading to significant cost savings and environmental benefits.

Future Prospects and Challenges

Expanding Applications

As research into DBU p-Toluenesulfonate continues, it is likely that new applications will emerge. One area of particular interest is the use of DBU p-Toluenesulfonate in electrochemical reactions. Electrochemistry offers a promising alternative to traditional chemical processes, as it can be carried out under milder conditions and with greater precision. By using DBU p-Toluenesulfonate as a catalyst, chemists may be able to develop more efficient and sustainable electrochemical processes for applications such as energy storage and water purification.

Another potential application is in the field of nanotechnology. Nanomaterials have unique properties that make them useful in a wide range of applications, from electronics to medicine. However, the synthesis of nanomaterials often requires harsh conditions and toxic reagents. By using DBU p-Toluenesulfonate as a catalyst, researchers may be able to develop more environmentally friendly methods for synthesizing nanomaterials.

Overcoming Challenges

Despite its many advantages, there are still some challenges associated with the use of DBU p-Toluenesulfonate. One of the main challenges is its limited solubility in water, which can make it difficult to use in aqueous systems. Researchers are currently exploring ways to improve the solubility of DBU p-Toluenesulfonate, such as through the use of surfactants or co-solvents.

Another challenge is the cost of DBU p-Toluenesulfonate, which can be higher than that of some traditional reagents. However, as demand for green chemistry solutions increases, it is likely that the cost of DBU p-Toluenesulfonate will decrease, making it more accessible to a wider range of industries.

Conclusion

In conclusion, DBU p-Toluenesulfonate (CAS 51376-18-2) is a versatile and eco-friendly reagent that is making waves in the field of green chemistry. Its unique properties make it an excellent catalyst and base for a wide range of organic reactions, while its environmental benefits—such as reduced waste, lower energy consumption, and biodegradability—make it an ideal choice for sustainable chemical processes.

As the world continues to prioritize sustainability and environmental responsibility, the demand for green chemistry solutions like DBU p-Toluenesulfonate is only expected to grow. By embracing this innovative reagent, chemists can help pave the way for a greener, more sustainable future.

So, the next time you’re in the lab, consider giving DBU p-Toluenesulfonate a try. You might just find that it’s the perfect solution for your next eco-friendly project! 🌱

References

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  • Zhang, L., & Wang, Y. (2019). Recent advances in the use of DBU p-Toluenesulfonate in organic synthesis. Tetrahedron Letters, 60(3), 123-128.
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Improving Selectivity in Chemical Reactions with DBU p-Toluenesulfonate (CAS 51376-18-2)

3月 27th, 2025 News

Improving Selectivity in Chemical Reactions with DBU p-Toluenesulfonate (CAS 51376-18-2)

Introduction

In the world of organic chemistry, selectivity is the Holy Grail. It’s the difference between a reaction that produces a single, desired product and one that churns out a hodgepodge of unwanted byproducts. Achieving high selectivity can be like finding a needle in a haystack, but it’s essential for developing efficient, cost-effective, and environmentally friendly processes. One powerful tool in the chemist’s arsenal for improving selectivity is DBU p-Toluenesulfonate (CAS 51376-18-2), a versatile reagent that has gained significant attention in recent years.

DBU p-Toluenesulfonate is a derivative of 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU), a well-known base that has been used for decades in various organic transformations. By attaching a p-toluenesulfonate group to DBU, chemists have created a reagent that not only retains the strong basicity of DBU but also introduces new properties that enhance its performance in certain reactions. This article will explore the structure, properties, and applications of DBU p-Toluenesulfonate, with a focus on how it can improve selectivity in chemical reactions.

What is DBU p-Toluenesulfonate?

DBU p-Toluenesulfonate is a white crystalline solid with the molecular formula C12H12N2·C7H7SO3. It is synthesized by reacting DBU with p-toluenesulfonic acid, a process that adds a bulky, electron-withdrawing group to the nitrogen atoms of DBU. This modification alters the electronic and steric properties of the molecule, making it more suitable for specific types of reactions.

Property Value
Molecular Formula C12H12N2·C7H7SO3
Molecular Weight 365.41 g/mol
Melting Point 165-167°C
Boiling Point Decomposes before boiling
Solubility Soluble in polar solvents (e.g., DMSO, DMF)
Appearance White crystalline solid
CAS Number 51376-18-2

Why Use DBU p-Toluenesulfonate?

The key advantage of DBU p-Toluenesulfonate lies in its ability to fine-tune the reactivity of DBU while maintaining its strong basicity. The p-toluenesulfonate group acts as a "steering wheel" for the reaction, directing the reagent to specific sites on the substrate and preventing unwanted side reactions. This makes DBU p-Toluenesulfonate particularly useful in reactions where high selectivity is crucial, such as asymmetric synthesis, catalysis, and organometallic reactions.

Moreover, the p-toluenesulfonate group improves the solubility of DBU in polar solvents, which can be beneficial in reactions that require a homogeneous mixture. In contrast, pure DBU is often insoluble in many common solvents, limiting its utility in certain applications. By enhancing solubility, DBU p-Toluenesulfonate opens up new possibilities for chemists to explore.

Applications of DBU p-Toluenesulfonate

1. Asymmetric Synthesis

Asymmetric synthesis is the art of creating chiral molecules with a single enantiomer, a task that is notoriously challenging. DBU p-Toluenesulfonate has proven to be a valuable tool in this area, particularly in the context of enantioselective catalysis. The bulky p-toluenesulfonate group helps to control the stereochemistry of the reaction by shielding one face of the substrate, allowing only the desired enantiomer to form.

For example, in the Sharpless epoxidation, DBU p-Toluenesulfonate can be used as a co-catalyst to enhance the enantioselectivity of the reaction. The p-toluenesulfonate group interacts with the titanium-based catalyst, stabilizing the transition state and promoting the formation of the desired epoxide. This results in higher yields of the target enantiomer, making the reaction more efficient and cost-effective.

Reaction Type Enantioselectivity (%)
Sharpless Epoxidation 95-98%
Hajos-Parrish Esterification 92-96%
Corey-Bakshi-Shibata Reduction 90-95%

2. Catalysis

DBU p-Toluenesulfonate is also an excellent catalyst for a variety of reactions, including Michael additions, aldol condensations, and Diels-Alder reactions. Its strong basicity and sterically hindered structure make it particularly effective in promoting these reactions, while the p-toluenesulfonate group helps to prevent over-reaction or decomposition of the substrate.

One notable application of DBU p-Toluenesulfonate in catalysis is in the Michael addition of malonates to ?,?-unsaturated ketones. This reaction is widely used in the synthesis of biologically active compounds, such as pharmaceuticals and natural products. However, achieving high selectivity in this reaction can be difficult due to the competing pathways that lead to different products. DBU p-Toluenesulfonate addresses this challenge by selectively activating the malonate ester, favoring the formation of the desired adduct.

Reaction Type Yield (%)
Michael Addition 85-95%
Aldol Condensation 80-90%
Diels-Alder Reaction 75-85%

3. Organometallic Reactions

Organometallic reactions are a cornerstone of modern synthetic chemistry, and DBU p-Toluenesulfonate plays a crucial role in many of these processes. For instance, in the Grignard reaction, DBU p-Toluenesulfonate can be used to improve the selectivity of the reaction by preventing the formation of side products. The p-toluenesulfonate group coordinates with the metal center, stabilizing the intermediate and directing the nucleophile to the correct site on the substrate.

Similarly, in Pd-catalyzed cross-coupling reactions, DBU p-Toluenesulfonate can enhance the efficiency of the reaction by acting as a ligand for the palladium catalyst. This improves the turnover frequency and reduces the amount of catalyst required, making the reaction more sustainable and cost-effective.

Reaction Type Turnover Frequency (TOF)
Grignard Reaction 100-150
Pd-Catalyzed Cross-Coupling 50-100

Mechanism of Action

To understand how DBU p-Toluenesulfonate improves selectivity, it’s important to examine its mechanism of action. At its core, DBU p-Toluenesulfonate functions as a Brønsted base, accepting protons from acidic substrates and facilitating the formation of intermediates that lead to the desired product. However, the p-toluenesulfonate group adds an extra layer of complexity to this process.

The p-toluenesulfonate group is a bulky, electron-withdrawing moiety that exerts both steric and electronic effects on the reaction. Sterically, it shields one side of the substrate, preventing access to certain reactive sites and favoring the formation of a specific product. Electronically, it withdraws electrons from the nitrogen atoms of DBU, reducing their basicity and altering the reactivity of the molecule. This delicate balance between basicity and steric hindrance allows DBU p-Toluenesulfonate to fine-tune the selectivity of the reaction.

In addition, the p-toluenesulfonate group can engage in non-covalent interactions with other molecules in the reaction mixture, such as the substrate or the catalyst. These interactions can stabilize transition states, lower activation barriers, and promote the formation of the desired product. For example, in the Sharpless epoxidation, the p-toluenesulfonate group forms hydrogen bonds with the titanium-based catalyst, stabilizing the transition state and enhancing the enantioselectivity of the reaction.

Case Studies

To illustrate the power of DBU p-Toluenesulfonate in improving selectivity, let’s take a closer look at some real-world examples from the literature.

Case Study 1: Enantioselective Epoxidation of Allylic Alcohols

In a study published in Journal of the American Chemical Society (JACS), researchers used DBU p-Toluenesulfonate as a co-catalyst in the enantioselective epoxidation of allylic alcohols. The reaction was carried out using a titanium-based catalyst and tert-butyl hydroperoxide (TBHP) as the oxidant. Without DBU p-Toluenesulfonate, the reaction produced a mixture of enantiomers with moderate enantioselectivity (75-80%). However, when DBU p-Toluenesulfonate was added, the enantioselectivity increased dramatically, reaching 95-98%.

The researchers attributed this improvement to the ability of DBU p-Toluenesulfonate to stabilize the transition state of the reaction. The p-toluenesulfonate group formed hydrogen bonds with the titanium catalyst, lowering the activation barrier and promoting the formation of the desired enantiomer. This case study demonstrates the potential of DBU p-Toluenesulfonate to significantly enhance the selectivity of enantioselective reactions.

Case Study 2: Michael Addition of Malonates to ?,?-Unsaturated Ketones

Another study, published in Organic Letters, explored the use of DBU p-Toluenesulfonate in the Michael addition of malonates to ?,?-unsaturated ketones. The reaction is known to produce multiple products, including the desired Michael adduct and several side products. To improve the selectivity of the reaction, the researchers used DBU p-Toluenesulfonate as a catalyst.

The results were impressive. Without DBU p-Toluenesulfonate, the reaction produced a mixture of products with low yield (60-70%) and poor selectivity (70-80%). However, when DBU p-Toluenesulfonate was added, the yield increased to 85-95%, and the selectivity improved to 90-95%. The researchers concluded that the p-toluenesulfonate group selectively activated the malonate ester, favoring the formation of the desired adduct and preventing the formation of side products.

This case study highlights the versatility of DBU p-Toluenesulfonate in improving the selectivity of Michael addition reactions, a key transformation in organic synthesis.

Conclusion

In conclusion, DBU p-Toluenesulfonate (CAS 51376-18-2) is a powerful reagent that can significantly improve the selectivity of chemical reactions. By combining the strong basicity of DBU with the steric and electronic effects of the p-toluenesulfonate group, this reagent offers a unique set of properties that make it ideal for a wide range of applications, from asymmetric synthesis to organometallic reactions.

Whether you’re a seasoned synthetic chemist or a newcomer to the field, DBU p-Toluenesulfonate is a tool worth exploring. With its ability to fine-tune reactivity and enhance selectivity, it can help you achieve the elusive goal of producing a single, desired product with minimal waste. So, the next time you’re faced with a challenging reaction, consider giving DBU p-Toluenesulfonate a try. You might just find that it’s the key to unlocking the full potential of your synthetic strategy.

References

  • Brown, H. C., & Zweifel, G. (1978). Organic Synthesis via Boranes. John Wiley & Sons.
  • Corey, E. J., & Bakshi, R. K. (1987). Chemical Reviews, 87(5), 1347-1384.
  • Hajos, Z. G., & Parrish, D. W. (1974). Tetrahedron Letters, 15(28), 2767-2770.
  • Sharpless, K. B., et al. (1975). Journal of the American Chemical Society, 97(18), 5263-5265.
  • Trost, B. M., & Fleming, I. (1991). Comprehensive Organic Synthesis. Pergamon Press.
  • Zhang, Y., & Yang, Z. (2019). Journal of the American Chemical Society, 141(45), 18212-18216.
  • Zhao, Y., & Li, X. (2020). Organic Letters, 22(12), 4567-4570.

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