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Synthesis of heterocyclic compounds
Research Guide
What is Synthesis of heterocyclic compounds?
Synthesis of heterocyclic compounds is the preparation of cyclic organic structures containing heteroatoms such as nitrogen, oxygen, or sulfur, often through strategies like annulation, catalyzed reactions, and multicomponent reactions involving ketene dithioacetals to produce functionalized heterocycles including thiophenes and pyridinones.
This field encompasses 25,771 works focused on regioselective synthesis of highly functionalized heterocycles. Key methods include annulation reactions and multicomponent processes using ketene dithioacetals. Common targets are thiophenes and pyridinones produced via catalyzed reactions.
Topic Hierarchy
Research Sub-Topics
Ketene Dithioacetal Chemistry
This sub-topic covers synthesis, reactivity, and applications of ketene dithioacetals as synthons for heterocycles. Researchers explore regioselective functionalizations and their role in C-C bond formations.
Regioselective Heterocycle Synthesis
Studies develop methods ensuring precise regiochemistry in heterocycle construction via annulation or cycloadditions. Focus includes control elements like directing groups and chiral auxiliaries.
Multicomponent Reactions for Heterocycles
This area investigates one-pot MCRs involving ketene dithioacetals to generate complex heterocycles efficiently. Research optimizes conditions for thiophenes, pyrroles, and pyridines with high diversity.
Catalyzed Annulation Reactions
Explores transition-metal or organocatalyzed annulations of ketene dithioacetals with nucleophiles/electrophiles. Studies mechanistic insights, catalyst design, and scope for fused heterocycles.
Synthesis of Functionalized Thiophenes
Researchers develop routes to densely substituted thiophenes using dithioacetal precursors via sulfur extrusion or rearrangement. Applications target materials and agrochemicals with tailored properties.
Why It Matters
Heterocyclic compounds synthesized through these methods serve as core structures in pharmaceuticals with applications in antimalarial, anticonvulsant, and antitumor agents. For example, quinolines and related heterocycles exhibit antimalarial activity as detailed in "Quinolines and structurally related heterocycles as antimalarials" by Kaur et al. (2010), which reviews their pharmacological potential. Hydrazone derivatives, synthesized from heterocyclic precursors, show antimicrobial and antitumoral effects, with 1157 citations underscoring their biological relevance as reported in "Biological Activities of Hydrazone Derivatives" by Rollas and Küçükgüzel (2007). Spirocyclic scaffolds incorporating heterocycles enhance drug discovery by providing three-dimensional structures, as demonstrated in "The use of spirocyclic scaffolds in drug discovery" by Zheng et al. (2014) with 990 citations.
Reading Guide
Where to Start
"Heterocyclen aus CH‐aciden Nitrilen, VIII. 2‐Amino‐thiophene aus methylenaktiven Nitrilen, Carbonylverbindungen und Schwefel" by Gewald et al. (1966), as it provides a foundational one-pot method for 2-aminothiophenes using accessible reagents at room temperature.
Key Papers Explained
Gewald et al. (1966) established the synthesis of 2-aminothiophenes from nitriles, carbonyls, and sulfur, which connects to Cava and Levinson (1985) on thionation reagents that enable sulfur introduction in related heterocycles. Kühn and Kratz (1993) build on this by reducing thiones to imidazol-2-ylidenes, while Henry (2004) extends de novo strategies to pyridines. Kaur et al. (2010) applies quinolines from such syntheses to antimalarials, linking organic methods to pharmacology.
Paper Timeline
Most-cited paper highlighted in red. Papers ordered chronologically.
Advanced Directions
Current work emphasizes ketene dithioacetal annulations for functionalized thiophenes and pyridinones via catalyzed multicomponent reactions, focusing on regioselectivity. No recent preprints or news available, so frontiers follow from established methods like Gewald synthesis extensions.
Papers at a Glance
| # | Paper | Year | Venue | Citations | Open Access |
|---|---|---|---|---|---|
| 1 | Neuroactive steroids | 1992 | The FASEB Journal | 1.3K | ✓ |
| 2 | Biological Activities of Hydrazone Derivatives | 2007 | Molecules | 1.2K | ✓ |
| 3 | The use of spirocyclic scaffolds in drug discovery | 2014 | Bioorganic & Medicinal... | 990 | ✓ |
| 4 | Imidazolylidenes, imidazolinylidenes and imidazolidines | 1999 | Tetrahedron | 938 | ✕ |
| 5 | 1,3-Dimethyl-4-imidazolinyliden-(2)-pentacarbonylchrom ein neu... | 1968 | Journal of Organometal... | 840 | ✕ |
| 6 | Heterocyclen aus CH‐aciden Nitrilen, VIII. 2‐Amino‐thiophene a... | 1966 | Chemische Berichte | 770 | ✕ |
| 7 | Quinolines and structurally related heterocycles as antimalarials | 2010 | European Journal of Me... | 709 | ✓ |
| 8 | De novo synthesis of substituted pyridines | 2004 | Tetrahedron | 700 | ✕ |
| 9 | Thionation reactions of lawesson's reagents | 1985 | Tetrahedron | 656 | ✕ |
| 10 | Synthesis of Imidazol-2-ylidenes by Reduction of Imidazole-2(3... | 1993 | Synthesis | 648 | ✕ |
Frequently Asked Questions
What is the Gewald synthesis for thiophenes?
The Gewald reaction involves aliphatic ketones, aldehydes, or β-dicarbonyl compounds reacting with methylenactive nitriles and sulfur in the presence of amines at room temperature to form 2-aminothiophenes. A variant uses sulfur on vinylogous methylenactive nitriles. This method is described in "Heterocyclen aus CH‐aciden Nitrilen, VIII. 2‐Amino‐thiophene aus methylenaktiven Nitrilen, Carbonylverbindungen und Schwefel" by Gewald et al. (1966).
How are imidazol-2-ylidenes synthesized?
Imidazol-2-ylidenes are prepared by reducing imidazole-2(3H)-thiones, which are obtained from N,N-dialkylthioureas and 3-hydroxy-2-butanone. Treatment with potassium in boiling tetrahydrofuran yields the carbene complexes in excellent yields. This is outlined in "Synthesis of Imidazol-2-ylidenes by Reduction of Imidazole-2(3H)-thiones" by Kühn and Kratz (1993).
What role do Lawesson's reagents play in heterocyclic synthesis?
Lawesson's reagents facilitate thionation reactions to introduce sulfur into heterocyclic frameworks. They convert carbonyl groups to thiocarbonyl equivalents in thione and dithioacetal syntheses. Details appear in "Thionation reactions of lawesson's reagents" by Cava and Levinson (1985).
How are substituted pyridines synthesized de novo?
De novo synthesis of substituted pyridines employs various cyclization strategies tailored to functional group incorporation. Methods focus on regioselective annulation and multicomponent approaches. This is reviewed in "De novo synthesis of substituted pyridines" by Henry (2004).
What are key applications of synthesized heterocycles?
Synthesized heterocycles underpin neuroactive steroids modulating neuron excitability via neurotransmitter receptors, as in "Neuroactive steroids" by Paul and Purdy (1992). They also form spirocyclic scaffolds in drug discovery for structural diversity, per "The use of spirocyclic scaffolds in drug discovery" by Zheng et al. (2014).
Open Research Questions
- ? How can ketene dithioacetals enable more regioselective annulations for complex polysubstituted thiophenes beyond Gewald conditions?
- ? What catalytic systems improve multicomponent reactions for pyridinone synthesis from methylenactive nitriles?
- ? Can thionation with Lawesson's reagents be adapted for continuous-flow synthesis of imidazolinylidenes?
- ? Which substituents on spirocyclic heterocycles optimize binding to antimalarial targets like those in quinolines?
- ? How do reductive conditions for imidazol-2-ylidenes scale to asymmetric variants?
Recent Trends
The field includes 25,771 works with a focus on ketene dithioacetal chemistry for regioselective heterocycle synthesis, but growth rate over 5 years is not available.
Highly cited papers like "Biological Activities of Hydrazone Derivatives" by Rollas and Küçükgüzel (2007, 1157 citations) highlight sustained interest in pharmacological applications.
No recent preprints or news in the last 12 months.
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