TCFH-NMI Ketone Synthesis Inspired by Nucleophilicity Scales
Johnson H Ho1, Grant H Miller1, Kasey K Chung1
1Department of Chemistry, Harvey Mudd College, 301 Platt Boulevard, Claremont, California 91711, United States.
Organic Letters
|October 7, 2024
Summary
A new method uses TCFH-NMI to synthesize ketones from carboxylic acids at room temperature. Pyrroles and indoles with high nucleophilicity (N ≥ 10) are effective carbon nucleophiles in this reaction.
Area of Science:
- Organic Chemistry
- Synthetic Chemistry
Background:
- Carboxylic acids are versatile starting materials in organic synthesis.
- Mild and efficient methods for ketone synthesis are highly sought after.
- Existing methods for ketone synthesis often require harsh conditions or specific reagents.
Purpose of the Study:
- To develop a mild, room-temperature method for synthesizing ketones directly from carboxylic acids.
- To explore the utility of N,N,N',N'-Tetramethylchloroformamidinium hexafluorophosphate (TCFH) and N-methylimidazole (NMI) in ketone synthesis.
- To identify suitable carbon nucleophiles for this transformation using the Mayr nucleophilicity scale.
Main Methods:
- Utilized the TCFH-NMI reagent system for activating carboxylic acids.
- Employed the Mayr nucleophilicity scale to quantify and compare the reactivity of various carbon nucleophiles.
- Investigated the reaction of activated carboxylic acids with nucleophiles, focusing on pyrroles and indoles.
Main Results:
- Successfully synthesized ketones directly from carboxylic acids at room temperature using the TCFH-NMI system.
- Identified pyrroles and indoles as effective carbon nucleophiles for this reaction, provided their Mayr nucleophilicity (N) value is 10 or greater.
- Demonstrated the mildness and practicality of the developed synthetic route.
Conclusions:
- The TCFH-NMI reagent system provides a mild and efficient pathway for ketone synthesis from carboxylic acids.
- The Mayr nucleophilicity scale is a valuable tool for predicting and selecting appropriate carbon nucleophiles for this transformation.
- This method offers a practical alternative for synthesizing ketones, particularly those derived from electron-rich heterocycles like pyrroles and indoles.
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