Categories: Synthesis of N-Heterocycles >
Synthesis of pyridazines
An unexpected C-C bond cleavage in the absence of metal enables an efficient approach toward 3,6-diarylpyridazines and 6-arylpyridazin-3-ones from simple and commercially available 1,3-dicarbonyl compounds and methyl ketones.
Q. Gao, Y. Zhu, M. Lian, M. Liu, J. Yuan, G. Yin, A. Wu, J. Org. Chem., 2012, 77, 9865-9870.
Cu(II)-catalyzed aerobic 6-endo-trig cyclizations provide 1,6-dihydropyridazines and pyridazines via the judicious choice of reaction solvent. Whereas 1,6-dihydropyridazines were obtained in good yields with MeCN as the reaction solvent, employment of AcOH directly afforded pyridazines in good yields.
Z. Fan, Z. Pan, L. Huang, J. Cheng, J. Org. Chem., 2019, 84, 4236-4245.
A copper-promoted 6-endo-trig cyclization of readily available β,γ-unsaturated hydrazones enables an efficient synthesis of a series of 1,6-dihydropyridazines with good yields, high functional group tolerance, and remarkable regioselectivity under mild conditions. Importantly, the 1,6-dihydropyridazines can be efficiently converted to biologically important pyridazines in the presence of NaOH.
Y.-Q. Guo, M.-N. Zhao, Z.-H. Ren, Z.-H. Guan, Org. Lett., 2018, 20, 3337-3340.