Aza Diels-Alder Reactions of Nitriles, N, N-Dimethylhydrazones, and Oximino Ethers. Application in Formal [2 + 2 + 2] Cycloadditions for the Synthesis of Pyridines
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Author(s)
Hamzik, Philip Jonathan
Goutierre, Anne-Sophie
Sakai, Takeo
Danheiser, Rick Lane
Date Issued
December 2017
Journal
The Journal of Organic Chemistry
Publisher
American Chemical Society (ACS)
Citation
Hamzik, Philip J., Anne-Sophie Goutierre, Takeo Sakai, and Rick L. Danheiser. “Aza Diels–Alder Reactions of Nitriles, N,N-Dimethylhydrazones, and Oximino Ethers. Application in Formal [2 + 2 + 2] Cycloadditions for the Synthesis of Pyridines.” The Journal of Organic Chemistry 82, no. 24 (December 2017): 12975–12991.
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Author's final manuscript
Abstract
Metal-free, formal [2 + 2 + 2] cycloaddition st rategies for the synthesis of polycyclic pyridine derivatives are described. The overall transformation proceeds via a two-stage pericyclic cascade mechanism. In the first step, an intramolecular propargylic ene reaction generates a vinyl-allene that is necessarily locked in the s-cis conformation. This vinylallene exhibits exceptional reactivity as a Diels-Alder reaction partner and engages in [4 + 2] cycloadditions with normally unreactive aza dienophiles including unactivated cyano groups and heterosubstituted imine derivatives such as dimethylhydrazones and oximino ethers. Few examples of oximino ether Diels-Alder reactions have been reported previously and normal electron demand [4 + 2] cycloadditions of unactivated dialkylhydrazones are unprecedented. Overall this metal-free formal [2 + 2 + 2] cycloaddition provides access to polycyclic pyridine derivatives and complements transition metal-catalyzed [2 + 2 + 2] strategies.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/acs.joc.7b02503
