1-(1-Ethoxyethyl)-1H-pyrazole-4-boronic acid pinacol ester
[CAS# 1029716-44-6]

Identification

• Classification: Chemical reagent >> Organic reagent >> Ester
• Name: 1-(1-Ethoxyethyl)-1H-pyrazole-4-boronic acid pinacol ester
• Molecular Formula: C₁₃H₂₃BN₂O₃
• Molecular Weight: 266.14
• CAS Registry Number: 1029716-44-6
• EC Number: 689-230-6
• SMILES: B1(OC(C(O1)(C)C)(C)C)C2=CN(N=C2)C(C)OCC

Properties

• Density: 1.06

Safety Data

• Hazard Symbols: GHS02;GHS07 Danger
• Risk Statements: H228-H252-H302-H312-H315-H319-H332-H335
• Safety Statements: P210-P235-P240-P241-P261-P264-P264+P265-P270-P271-P280-P301+P317-P302+P352-P304+P340-P305+P351+P338-P317-P319-P321-P330-P332+P317-P337+P317-P362+P364-P370+P378-P403+P233-P405-P407-P410-P413-P420-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute toxicity	Acute Tox.	4	H302
Specific target organ toxicity - single exposure	STOT SE	3	H335
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H312
Acute toxicity	Acute Tox.	4	H332
Eye irritation	Eye Irrit.	2	H319
Flammable solids	Flam. Sol.	2	H228
Self-heating substances or mixtures	Self-heat.	2	H252

Discovery and Applications

1-(1-Ethoxyethyl)-1H-pyrazole-4-boronic acid pinacol ester is a specialized boronic ester that has gained attention in organic synthesis, particularly in the field of Suzuki-Miyaura cross-coupling reactions. The discovery of this compound has provided chemists with a versatile building block that facilitates the formation of carbon-carbon bonds, a fundamental process in the construction of complex organic molecules.

The synthesis of 1-(1-Ethoxyethyl)-1H-pyrazole-4-boronic acid pinacol ester was driven by the need for more stable and reactive boronic esters that could be efficiently utilized in cross-coupling reactions. Traditional boronic acids, though effective, often suffer from issues such as instability and poor solubility in organic solvents. By incorporating a pinacol ester moiety, which is known for its stability and enhanced solubility, this compound overcomes these limitations, making it a more reliable reagent in various synthetic applications.

The structure of 1-(1-Ethoxyethyl)-1H-pyrazole-4-boronic acid pinacol ester features a pyrazole ring substituted with a boronic acid group protected by a pinacol ester and an ethoxyethyl group at the nitrogen position. This specific configuration not only improves the stability of the boronic acid but also increases the electron density on the pyrazole ring, making it more reactive in cross-coupling reactions. The presence of the ethoxyethyl group further enhances the compound's solubility, facilitating its use in a broader range of organic solvents.

In practical applications, 1-(1-Ethoxyethyl)-1H-pyrazole-4-boronic acid pinacol ester has been widely used in the synthesis of pharmaceuticals, agrochemicals, and materials science. Its role in Suzuki-Miyaura cross-coupling reactions has been particularly prominent, where it serves as a boron-containing reagent that reacts with aryl halides to form biaryl compounds. These biaryl compounds are crucial intermediates in the synthesis of various biologically active molecules and functional materials.

One of the key advantages of using this boronic ester in Suzuki-Miyaura coupling is its ability to provide high yields under mild reaction conditions. The stability of the pinacol ester allows for reactions to be conducted at lower temperatures, reducing the risk of side reactions and decomposition of sensitive functional groups. Additionally, the compound's enhanced solubility in organic solvents ensures better reaction homogeneity, leading to more consistent and reproducible results.

Beyond its use in cross-coupling reactions, 1-(1-Ethoxyethyl)-1H-pyrazole-4-boronic acid pinacol ester has also been explored in the development of novel materials and as a key intermediate in the synthesis of heterocyclic compounds. The versatility of this compound in various synthetic routes highlights its importance as a valuable tool in modern organic chemistry.

The discovery and application of 1-(1-Ethoxyethyl)-1H-pyrazole-4-boronic acid pinacol ester have significantly contributed to the advancement of synthetic methodologies, enabling the efficient construction of complex molecular architectures. Its utility in diverse chemical transformations continues to expand, reflecting its growing importance in both academic research and industrial applications.

References

2019. Synthesis and Characterization of Compounds Potentially Related to the Janus Kinase Inhibitor Baricitinib. Russian Journal of Organic Chemistry, 55(10).
DOI: 10.1134/s1070428019100166