Metalation of Pyridazine, Cinnoline, and Phthalazine

Selective and Stepwise Functionalization of the Pyridazine Scaffold by Using Thio-Substituted Pyridazine Building Blocks

We described a regioselective tri- and tetra-functionalization of the pyridazine scaffold using two readily available building blocks: 3-alkylthio-6-chloropyridazine and 3,4-bis(methylthio)-6-chloropyridazine by performing selective metalations with TMPMgCl ⋅ LiCl and catalyst-tuned cross-coupling reactions with arylzinc halides. Several of the resulting pyridazines were converted into more elaborated N-heterocycles such as thieno[2,3-c]pyridazines and 1H-pyrazolo[3,4-c]pyridazines.

Autoxidation of 4-Hydrazinylquinolin-2(1H)-one; Synthesis of Pyridazino[4,3-c:5,6-c']diquinoline-6,7(5H,8H)-diones

An efficient synthesis of a series of pyridazino[4,3-c:5,6-c']diquinolines was achieved via the autoxidation of 4-hydrazinylquinolin-2(1H)-ones. IR, NMR (¹H and ¹³C), mass spectral data, and elemental analysis were used to fit and elucidate the structures of the newly synthesized compounds. X-ray structure analysis and theoretical calculations unequivocally proved the formation of the structure. The possible mechanism for the reaction is also discussed.

Synthesis and antifungal activity of imidazo[1,2-b]pyridazine derivatives against phytopathogenic fungi

A series of 3,6-disubstituted imidazo[1,2-b]pyridazine derivatives have been synthesized and characterized with spectroscopic analyses. The antifungal activities of these compounds against nine phytopathogenic fungi were evaluated by the mycelium growth rate method. The in vitro antifungal bioassays indicated that most of compounds displayed excellent and broad-spectrum antifungal activities. Especially, compounds 4a, 4c, 4d, 4l and 4r exhibited 1.9-25.5 fold more potent than the commercially available fungicide hymexazol against Corn Curvalaria Leaf Spot (CL), Alternaria alternate (AA), Pyricularia oryzae (PO) and Alternaria brassicae (AB) strains. Structure-activity relationship analysis showed that the enhanced antifungal activity is significantly affected by the substituents on the benzene ring and pyridazine ring.

Deprotometalation-iodolysis and computed CH acidity of 1,2,3- and 1,2,4-triazoles. Application to the synthesis of resveratrol analogues

1-Aryl- and 2-aryl-1,2,3-triazoles were synthesized by N-arylation of the corresponding azoles using aryl iodides. The deprotometalations of 1-phenyl-1,2,3-triazole and -1,2,4-triazole were performed using a 2,2,6,6-tetramethylpiperidino-based mixed lithium-zinc combination and occurred at the most acidic site, affording by iodolysis the 5-substituted derivatives. Dideprotonation was noted from 1-(2-thienyl)-1,2,4-triazole by increasing the amount of base. From 2-phenyl-1,2,3-triazoles, and in particular from 2-(4-trifluoromethoxy)phenyl-1,2,3-triazole, reactions at the 4 position of the triazolyl, but also ortho to the triazolyl on the phenyl group, were observed. The results were analyzed with the help of the CH acidities of the substrates, determined in THF solution using the DFT B3LYP method. 4-Iodo-2-phenyl-1,2,3-triazole and 4-iodo-2-(2-iodophenyl)-1,2,3-triazole were next involved in Suzuki coupling reactions to furnish the corresponding 4-arylated and 4,2'-diarylated derivatives. When evaluated for biological activities, the latter (which are resveratrol analogues) showed moderate antibacterial activity and promising antiproliferative effect against MDA-MB-231 cell line.