Cycloamination strategies for renewable N-heterocycles

Biomass resources have infinite possibilities for introducing nitrogen, sulfur, or phosphorus heteroatoms into their structures by virtue of controllable carbonheteroatom bond formation. In this review, cycloamination approaches for thermal (catalyst-free) and catalytic transformation of biomass fee...

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Bibliographic Details
Published in:Green chemistry : an international journal and green chemistry resource : GC 2020-01, Vol.22 (3), p.582-611
Main Authors: Li, Hu, Guo, Haixin, Fang, Zhen, Aida, Taku Michael, Smith, Richard Lee
Format: Article
Language:English
Subjects:
Benzimidazoles
Biomass
Catalysts
Green chemistry
Heterocyclic compounds
Indoles
Nitrogen
Nitrogen sources
Phosphorus
Pyrazines
Pyrazoles
Pyridines
Pyrroles
Reaction mechanisms
Substrates
Sulfur
Thermal transformations
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Summary:Biomass resources have infinite possibilities for introducing nitrogen, sulfur, or phosphorus heteroatoms into their structures by virtue of controllable carbonheteroatom bond formation. In this review, cycloamination approaches for thermal (catalyst-free) and catalytic transformation of biomass feedstocks into N-heterocyclic molecules including mechanistic pathways are analyzed. Bottom-up (small molecule substrates) and top-down (large molecule substrates) are considered. Sustainable routes for synthesis of five-membered (pyrroles, pyrrolidones, pyrazoles, imidazoles), six-membered (pyridines, pyrazines), fused (indoles, benzimidazoles), and other relevant azaheterocycles are critically assessed. Production of biomass-derived six-, seven-, and eight-membered as well as fused N-heterocyclic compounds with present approaches have relatively low selectivities. Attention to methods for forming analogous sulfur or phosphorus heteroatom compounds from biomass resources using either bottom-up or top-down strategies appear to have been greatly overlooked. Synthetic auxiliaries (heating modes, nitrogen sources) that enhance reaction efficiency and tunability of N-heterocyclic ring size/type are considered and plausible reaction mechanisms for pivotal pathways are developed. Efficient amination strategies for synthesis of N-heterocycles from functional molecules (bottom-up) or from biomass (top-down) via sustainable CN/CX bond chemistry.
ISSN:1463-9262
1463-9270
DOI:10.1039/c9gc03655e