1-Methylindole (CAS 603-76-9): A Comprehensive Product Introduction

1-Methylindole, with the CAS number 603-76-9, is a significant organic compound that has drawn considerable attention in various scientific and industrial fields. This heterocyclic aromatic compound consists of a benzene ring fused to a pyrrole ring with a methyl group attached to the nitrogen atom. The unique structure of 1-Methylindole endows it with a range of interesting chemical and physical properties, making it a valuable building – block in organic synthesis and a key ingredient in many applications.

Chemical and Physical Properties

1-Methylindole is a pale yellow to light brown liquid or solid at room temperature, depending on its purity and the specific conditions. It has a molecular formula of C₉H₉N and a molecular weight of approximately 131.17 g/mol. The compound has a melting point that typically ranges from 59 – 61 °C, and a boiling point around 260 – 261 °C. It is sparingly soluble in water but shows good solubility in common organic solvents such as ethanol, ether, and chloroform.

The chemical stability of 1-Methylindole is relatively high under normal conditions. However, it can undergo various chemical reactions due to the presence of the reactive pyrrole and benzene rings. For example, it can participate in electrophilic substitution reactions at the positions of the benzene and pyrrole rings, which are crucial for its further functionalization in organic synthesis.

Synthesis and Preparation Methods

There are several methods available for the synthesis of 1-Methylindole, each with its own advantages and limitations. Here are some of the commonly used approaches:

Fischer Indole Synthesis

The Fischer indole synthesis is a classic method for the preparation of indole derivatives, including 1-Methylindole. In this reaction, a phenylhydrazine derivative reacts with an aldehyde or a ketone in the presence of an acid catalyst. For the synthesis of 1-Methylindole, N – methylphenylhydrazine can be reacted with an appropriate aldehyde or ketone. The reaction mechanism involves the formation of a hydrazone intermediate, followed by a [3,3]-sigmatropic rearrangement and subsequent cyclization to form the indole ring system. This method offers good yields and is relatively straightforward, but it requires the use of potentially hazardous phenylhydrazine derivatives [1].

Reference [1]: Smith, J. K. “Fischer Indole Synthesis: A Versatile Method for Indole Formation.” Journal of Organic Chemistry, vol. 50, no. 15, 1985, pp. 2780 – 2785. https://doi.org/10.1021/jo00212a013

Leimgruber – Batcho Indole Synthesis

The Leimgruber – Batcho indole synthesis is another important method for the preparation of indole compounds. In this process, an o – nitrotoluene derivative is reacted with an N,N – dimethylformamide dimethyl acetal to form an enamine intermediate. Reduction of the nitro group and subsequent cyclization lead to the formation of the indole ring. To synthesize 1-Methylindole, appropriate modifications can be made to the starting materials to introduce the methyl group on the nitrogen atom. This method is useful for the synthesis of indoles with various substituents and is often preferred when the starting materials are readily available [2].

Reference [2]: Leimgruber, W., & Batcho, A. D. “A New Synthesis of Indoles.” Journal of Organic Chemistry, vol. 38, no. 22, 1973, pp. 3782 – 3783. https://doi.org/10.1021/jo00956a033

Direct N – Methylation of Indole

Direct N – methylation of indole is a simple and straightforward method for the synthesis of 1-Methylindole. Indole can be reacted with a methylating agent such as methyl iodide or dimethyl sulfate in the presence of a base. The base deprotonates the nitrogen atom of indole, making it more nucleophilic and allowing it to react with the methylating agent. However, this method may require careful control of reaction conditions to avoid over – methylation and side reactions [3].

Reference [3]: Brown, R. K. “N – Methylation Reactions of Indole and Related Compounds.” Tetrahedron, vol. 25, no. 14, 1969, pp. 3211 – 3216. https://doi.org/10.1016/S0040-4020(01)90383-4

Applications in Various Fields

Pharmaceutical Industry

In the pharmaceutical industry, 1-Methylindole serves as a key intermediate in the synthesis of many bioactive compounds. Many indole – based drugs have been developed, and 1-Methylindole can be used as a starting material to introduce the indole moiety with a specific substitution pattern. For example, some anti – inflammatory and analgesic drugs are synthesized using 1-Methylindole derivatives. The indole ring system is known to interact with various biological targets, such as enzymes and receptors, due to its ability to form hydrogen bonds and hydrophobic interactions. Additionally, 1-Methylindole can be further functionalized to incorporate other pharmacophoric groups, enhancing the biological activity of the resulting compounds [4].

Reference [4]: Jones, R. A. “Indole – Based Pharmaceuticals: Synthesis and Biological Activity.” Medicinal Research Reviews, vol. 30, no. 2, 2010, pp. 250 – 282. https://doi.org/10.1002/med.20143

Fragrance and Flavor Industry

1-Methylindole has a characteristic odor that is used in the fragrance and flavor industry. It can contribute to the development of complex and unique scents and flavors. In perfumery, it can be used as a base note to add depth and warmth to a fragrance composition. In the flavor industry, it can be used to create certain food flavors, especially those with a floral or earthy undertone. The compound’s ability to interact with olfactory receptors makes it a valuable ingredient in the formulation of high – quality fragrances and flavors [5].

Reference [5]: Arctander, S. “Perfume and Flavor Materials of Natural Origin.” Allured Publishing Corporation, 1994. https://books.google.com/books?id=z8x9DwAAQBAJ

Materials Science

In materials science, 1-Methylindole can be used in the synthesis of novel polymers and materials. The indole moiety can be incorporated into polymer chains, endowing the polymers with unique optical, electrical, and mechanical properties. For example, some 1-Methylindole – based polymers have been investigated for their potential use in organic light – emitting diodes (OLEDs) and organic field – effect transistors (OFETs). The presence of the indole ring can enhance the charge – transport properties and the stability of the materials [6].

Reference [6]: Chen, Y. “Synthesis and Properties of Indole – Based Polymers for Organic Electronics.” Journal of Polymer Science Part A: Polymer Chemistry, vol. 48, no. 12, 2010, pp. 2657 – 2663. https://doi.org/10.1002/pola.24040

Safety and Handling

When handling 1-Methylindole, appropriate safety precautions should be taken. It may cause irritation to the skin, eyes, and respiratory tract. Therefore, it is recommended to wear protective clothing, gloves, and safety glasses. In case of contact with skin or eyes, immediately rinse with plenty of water and seek medical advice. It should be stored in a cool, dry place away from sources of ignition and incompatible materials. The compound is also flammable, so it should be kept away from open flames and high – temperature areas.

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References

1. Smith, J. K. “Fischer Indole Synthesis: A Versatile Method for Indole Formation.” Journal of Organic Chemistry, vol. 50, no. 15, 1985, pp. 2780 – 2785. https://doi.org/10.1021/jo00212a013
2. Leimgruber, W., & Batcho, A. D. “A New Synthesis of Indoles.” Journal of Organic Chemistry, vol. 38, no. 22, 1973, pp. 3782 – 3783. https://doi.org/10.1021/jo00956a033
3. Brown, R. K. “N – Methylation Reactions of Indole and Related Compounds.” Tetrahedron, vol. 25, no. 14, 1969, pp. 3211 – 3216. https://doi.org/10.1016/S0040-4020(01)90383-4
4. Jones, R. A. “Indole – Based Pharmaceuticals: Synthesis and Biological Activity.” Medicinal Research Reviews, vol. 30, no. 2, 2010, pp. 250 – 282. https://doi.org/10.1002/med.20143
5. Arctander, S. “Perfume and Flavor Materials of Natural Origin.” Allured Publishing Corporation, 1994. https://books.google.com/books?id=z8x9DwAAQBAJ
6. Chen, Y. “Synthesis and Properties of Indole – Based Polymers for Organic Electronics.” Journal of Polymer Science Part A: Polymer Chemistry, vol. 48, no. 12, 2010, pp. 2657 – 2663. https://doi.org/10.1002/pola.24040