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Updated: Aug 5, 2026
11:51
Facile Preparation of 4-Substituted Quinazoline Derivatives
Published on: February 15, 2016
(3°)- or (4°)-3-Alkylquinolones via Heteroaromatic Claisen Rearrangement
Akash R Gogate1, Morgane Mando1, Andrew T McCabe1
1Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States.
Organic Letters
|July 27, 2026
Summary
Researchers developed a new method to synthesize challenging 3-alkylquinolone structures using nucleophilic aromatic substitution and Claisen rearrangement. This approach offers a novel route to potential anti-infective agents.
Area of Science:
- Organic Chemistry
- Medicinal Chemistry
Background:
- The synthesis of 3-alkylquinolones, particularly those with quaternary centers, is challenging using traditional condensation methods.
- Specific substitution patterns in quinolones are scarce in existing chemical literature.
Purpose of the Study:
- To develop an efficient synthesis for 3- and 4-alkylquinolones.
- To explore a novel synthetic route involving nucleophilic aromatic substitution and heteroaromatic Claisen rearrangement.
- To demonstrate the synthesis of quaternary endochin-like quinolones (4°-ELQs) as potential anti-infective agents.
Main Methods:
- Optimization of nucleophilic aromatic substitution between 2°-allyl alcohols and 4-sulfonylquinolines.
- Utilizing a 3°- or 4°-generating Claisen rearrangement.
- Investigating the energetics and stereoselectivity of the [3,3] sigmatropic rearrangement.
- Assessing the scope and limitations of the two-step synthetic sequence.
Main Results:
- Successful optimization of the nucleophilic aromatic substitution and Claisen rearrangement sequence.
- Detailed understanding of the reaction's energetics and stereoselectivity.
- Demonstrated proof-of-concept synthesis of quaternary endochin-like quinolones (4°-ELQs).
Conclusions:
- The developed two-step sequence provides a viable and novel method for synthesizing challenging 3- and 4-alkylquinolone motifs.
- This synthetic strategy opens a new avenue for developing novel anti-infective compounds.
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01:24[3,3] Sigmatropic Rearrangement of Allyl Vinyl Ethers: Claisen Rearrangement
The Claisen rearrangement is a [3,3] sigmatropic rearrangement of allyl vinyl ethers to unsaturated carbonyl compounds. The rearrangement is a concerted pericyclic reaction proceeding via a chair-like transition state.
01:07Preparation of 1° Amines: Hofmann and Curtius Rearrangement Overview
In the presence of an aqueous base and a halogen, primary amides can lose the carbonyl (as carbon dioxide) and undergo rearrangement to form primary amines. This reaction, called the Hofmann rearrangement, can produce primary amines (aryl and alkyl) in high yields without contamination by secondary and tertiary amines.
02:38Electrophilic Addition to Alkynes: Halogenation
Introduction
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.
02:35Electrophilic Addition to Alkynes: Hydrohalogenation
Electrophilic addition of hydrogen halides, HX (X = Cl, Br or I) to alkenes forms alkyl halides as per Markovnikov's rule, where the hydrogen gets added to the less substituted carbon of the double bond. Hydrohalogenation of alkynes takes place in a similar manner, with the first addition of HX forming a vinyl halide and the second giving a geminal dihalide.
02:45Alkyl Halides
Structural Properties
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
Alkyl halides are halogen-substituted alkanes wherein one or more hydrogen atoms of an alkane is replaced by a halogen atom such as fluorine, chlorine, bromine, or iodine. The carbon atom in an alkyl halide is bonded to the halogen atom, which is sp3-hybridized and exhibits a tetrahedral shape.
Unlike alkyl halides, compounds in which a halogen atom is bonded to an sp2 -hybridized carbon atom of a carbon-carbon double bond (C=C) are called vinyl halides. Whereas aryl...
01:27Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
Robinson annulation is a base-catalyzed reaction for the synthesis of 2-cyclohexenone derivatives from 1,3-dicarbonyl donors (such as cyclic diketones, β-ketoesters, or β-diketones) and α,β-unsaturated carbonyl acceptors. Named after Sir Robert Robinson, who discovered it, this reaction yields a six-membered ring with three new C–C bonds (two σ bonds and one π bond).