General Description

1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride is an organic salt with unique properties, including excellent thermal stability, good solubility in organic solvents, and notable catalytic activity. It has found widespread use in organic synthesis, especially in the catalytic cycloisomerization of 2-(iodoethynyl)aryl esters. However, caution must be exercised when handling this compound due to its potential safety hazards, including toxicity, skin and eye damage, and risks to aquatic life. Proper storage, handling, and personal protective equipment are crucial to mitigate these risks. In summary, 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride's unique properties make it a valuable tool in organic synthesis, but its potential safety hazards necessitate cautious handling and adherence to safety protocols.

Figure 1. 1,3-Bis (2,6-diisopropylphenyl) imidazolium chloride

Properties

1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride is a chemical compound with various interesting properties. This organic salt has gained attention in recent years due to its unique characteristics and potential applications in different fields. Firstly, 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride exhibits excellent thermal stability. It can withstand high temperatures without decomposition or degradation, making it suitable for use in thermal processes and reactions. Secondly, 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride possesses good solubility in common organic solvents, such as dichloromethane, chloroform, and acetone. This solubility property allows for easy handling and incorporation into various reaction systems. Additionally, 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride displays notable catalytic activity. It can act as an efficient catalyst in several organic transformations, including cross-coupling reactions, C-H activation, and Suzuki-Miyaura coupling, among others. Its catalytic performance can be attributed to the unique coordination properties of the imidazolium cation. In summary, 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride possesses excellent thermal stability, solubility in organic solvents, catalytic activity, and low toxicity. ¹

Applications

1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride, also known as "SIPr-HCl," is a popular N-heterocyclic carbene (NHC) ligand that has been widely used in organic synthesis. Specifically, it has been utilized in the catalytic cycloisomerization of 2-(iodoethynyl)aryl esters to generate 3-iodo-2-acyl benzofurans. a transformation, [1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene] gold(I) complex acts as a catalyst, promoting the formation of a new ring via a [1,2]-iodine shift and a C-O ring-closure step. The addition of a ketone functionality into the new ring is achieved through a C-C bond-formation process, with a β-iodo-substituted gold vinylidene serving as the intermediate species. One of the key advantages of using SIPr-HCl as the NHC ligand in this reaction is its ability to tolerate different substitution patterns at the phenol moiety, as well as a wide range of groups at the carboxylic fragment. This includes not only alkyl but also alkenyl, aryl, and heteroaryl groups, providing greater flexibility in substrate selection. Overall, the use of 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride in conjunction with [1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene] gold(I) complex has proven to be a valuable tool in the synthesis of 3-iodo-2-acyl benzofurans, offering a highly selective and efficient approach to this important class of compounds. ²

Safety

1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride is a chemical compound that requires careful handling due to its potential safety hazards. This substance is known to be fatal if swallowed, meaning that ingestion can lead to severe health consequences or even death. Therefore, it is crucial to prevent any accidental ingestion and ensure proper storage and handling procedures. In addition to the risks associated with ingestion, 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride can cause skin irritation upon contact. It may also induce an allergic skin reaction, highlighting the importance of using appropriate personal protective equipment such as gloves and lab coats when working with this compound. Furthermore, this chemical can cause serious eye damage and irritation. When inhaled, 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride may cause respiratory irritation. Adequate ventilation should be provided in areas where this compound is handled to prevent the inhalation of hazardous fumes or dust particles. It is worth noting that this substance is highly toxic to aquatic life, posing a significant environmental risk. Even small amounts released into water bodies can have long-lasting detrimental effects on aquatic organisms. Overall, due to its various safety hazards including toxicity, potential skin and eye damage, as well as risks to aquatic life, cautious handling, and adherence to safety protocols are paramount when working with 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride. ³

Reference

1. PubChem. COMPOUND SUMMARY: 1,3-Bis(2,6-diisopropylphenyl)imidazolium chloride. National Library of Medicine. 2005, PubChem CID: 2734913.

2. Fernández-Canelas P, Rubio E, González JM. Oxyacylation of Iodoalkynes: Gold(I)-Catalyzed Expeditious Access to Benzofurans. Org Lett. 2019 Aug 16;21(16):6566-6569.

3. Summary of Classification and Labelling: European Chemicals Agency, EC / List no. 627-434-9.