Synthesis of the dibenzo[f,h]phthalazine and dibenzo[f,h]cinnoline skeleton via a ‘Suzuki–Pd-catalyzed intramolecular arylation’ and a ‘Suzuki–Pschorr’ approach

New Pathways Towards Pyridazino-Fused Ring Systems

“…21 This finding also confirms that electronic properties of the C-halogen bond may play a decisive role in the Suzuki reaction. In the cross-coupling reaction of 9 with 2-bromophenylboronic acid, the usual reactivity order 22 of the C-X bond (C-Br > C-Cl) is reversed for two reasons: i) the C-Cl bond at the pyridazinone ring is strongly activated by its vinylogous carbamoyl chloride nature (and the presence of the para-nitrogen); ii) the conjugate base of the 2-bromophenylboronic acid retards both sterically and …”

“…The diazonium derivative 24 was prepared smoothly from 6-chloro-1,3-dimethylpyrimidine-2,4(1H,3H)-dione (21) in 3 steps via 22 and 23. However, treatment of 24 with sodium azide did not result in formation of the expected azide 25.…”

“…The 5-ortho-diazinophenylpyridazinone 12c was prepared from compound 9 in three steps (Scheme 17). 21 In a very simple way, upon letting the solution of diazonium salt 12c stand at room temperature, compound 42 could be isolated in 64% yield, i.e. in a higher overall yield (40% vs. 29%) than in case of the application of Suzuki and Heck-type reactions.…”

Reaction of chloropyridazin-3(2H)-ones with iodide. Part II.

“…The starting 5-chloro-2-methyl-6-phenylpyridazin-3(2H)-one 1 and 5-chloro-6-(2,4-dichlorophenyl)-2-methylpyridazin-3(2H)-one 3 were prepared according to the literature [12][13][14][15] while 4,5-dichloro-2-methyl-6-phenylpyridazin-3(2H)-one 2 was obtained by N-methylation of 4,5-dichloro-6-phenylpyridazin-3(2H)-one 6 with dimethyl sulphate in methanol-water as solvent at room temperature. Compound 6 was reported previously, 16 however, no experimental details or spectral data were given.…”

Synthesis of ortho-Functionalized 4-Aminomethylpyridazines as Substrate-Like Semicarbazide-Sensitive Amine Oxidase Inhibitors

“…Whereas catalytic hydrogenation of the nitrile 17 in acidic medium at 3.44 bar effected selective debenzylation at the tertiary amino group (together with reduction of the cyano group) to yield compound 18, the 2-benzyl residue in 17 could be selectively removed with AlCl 3 in toluene (in analogy to lit. [20][21][22][23][24][25][26] ), affording the 2-unsubstituted pyridazinone 19. When the latter was heated in phosphorus oxychloride at 110°C, the 3-chloropyridazine 20 was obtained in good yield.…”