Pyridazine, 3-chloro-6-phenyl

Aminopyridazinyl-4-chlorophenyl ketone reacts with hydrazine hydrate to yield 3-(4-chloro-phenyl)-1 //-pyrazolo[3,4-d]pyridazine <86JCS(Pl) 169>. 

Pyrazole (3 chloro,4 carboxy,1 methyl 5 sulfonamide) halosulfuron Pyrazole (1.4 dimethyl,2 chloro, 3 formyl) fenpyroximate Pyrazole (2 methyl, 3 amino, 4 carboxy) pyrazosulfuron Pyrazole (2 methyl,4 carboxy, ethyl ester) pyrazosulfuron Pyrazole (1 methyl,2 ethyl,4 chloro 5 carboxy) tebufenpyrad 5 Pyrazolone (1.3 dimethyl) benzofenap, pyrazolinate, pyrazoxyfen Pyridazine (1 phenyl 3 hydroxy, 6 oxo) pyridafenthion... 

Greenhouse evaluation in a random herbicide screen showed that 3-chloro-4-methyl-6-[m-(trifluoro-methyl)phenyl)pyridazine was sufficiently active to serve as a lead for a synthesis project. Related 3-chloropyridazines were prepared by a sequence based on the addition of acyl anion equivalents of substituted benzaldehydes to the appropriately substituted acrylate esters. Using 3-chloro-pyridazines as key intermediates, a variety of other 3-substituted-pyridazines were prepared. The effect of altering substitution at each position of the pyridazine and phenyl rings on herbicidal activity was examined. 

Pyrimidin-4-one, 2,5,6-triamino- N NMR, 3, 64 (78HCA2108) Pyrimido[4,5-d]pyridazin-5-amine, JV-benzyl-8-chloro-2-phenyl-pXa, UV, 3, 337 <76BSF(2)1549) Pyrimido[4,5-d]pyridazin-5-amine, JV-butyl-8-chloro-2-phenyl-... 

Imtdazo[4,5-d]pyridaztne, l-benzyl-4,7-dtchloro-nucleophtlic displacement reactions, 5, 629 Imidazo[l,5-6]pyridazine-5,7(3H,6H)-dione, 4-acetyl-2-phenyl-synthesis, 5, 651 Imidazo[l, 2-6]pyridazines reactions, 5, 628 synthesis, 5, 650 Imidazo[ 1,5-6]pyridazines synthesis, 5, 651 Imidazo[4,5-c]pyridazines reactions, 5, 628-629 synthesis, 5, 651 Imidazo[4,5-d]pyridazines reactions, 5, 629 synthesis, 5, 436, 468, 651-652 3H-Imidazo[l,2-6]pyridazin-2-one, 6-chloro-3-dichloromethylene-synthesis, 3, 355... 

Table V. 18 2/18 3-Ratios of Differently Substituted 2-phenyl-4-chloro-5-dimethylamino-pyridazin-3-ones Experimentally Found and Calculated after Equation 9.

On the other hand, 2-chloro-6-methyl-3,4-pyridinedicarboximide 309 was reacted with phenylhydrazine to yield the salt of A -phenylpyrido[3,4-<7]pyridazine 313 or 314. The iV-phenylaminoimide 310 was isomerized to the corresponding 2- and 3-phenyl isomers 311 and 312 under the influence of heating in methanolic solution of MeONa (Scheme 8) <1998FA468>. 

Treatment of 3-chloro-6-phenyl-l,2,4-triazine A with 1.1 equivalents of phenylacetonitrile in dry N.N-dimethylacetamide at 0°C in the presence of an excess of KOlBu for one hour followed by quenching of the reaction mixture with ice-water gave an 86% yield of a dinitrile B, C17H12N4. Treatment of B with 1 1 aqueous ammonia/acetone for one hour resulted in quantitative conversion into 3-amino-4,6-diphenylpyridazine, C. The triazine A was converted directly into the pyridazine C when DMF was used as solvent and the reaction mixture was quenched with aqueous acetic acid. 

There are few reports of the nitration of the pyridazines and pyrazines. The nitration of phenylpyridazines has been stated to occur exclusively in the phenyl ring (73MI1). The use of fuming nitric acid at 0°C forms only the 4-nitrophenyl derivative (95%), as does 4-chloro-2-phenyl-3-pyridazone (100%), and 4-amino-2-phenyl-3-pyridazone (60%) (47JCS549). 

A series of fluorine-18 labelled 1,2-diazabenzenes 6 have been synthesized28 in the reaction of high specific activity, NCA [18F]fluoride ion with various chloro-substituted pyridazines 7 (equation 8) in radiochemical yields ranging from 11 to 64% [24% yield for R = Me, 64% for R = 4-benzoyl, 11% for R = 4-fluorobenzoyl, 46% for R = (2-thienyl) carbonyl]. The rat biodistribution of pyridazine analogues, more polar than the corresponding phenyl derivatives, has been studied and their applications to radiopharmaceuticals are underway28. 

A Suzuki coupling of 5-chloro-2-methyl-6-phenyl-2H-pyridazin-3-one (10) ultimately led to diazino-fused indole 11 and cinnoline 12 and allowed access to a novel pyrimidoisoquinoline ring system in a one-pot fashion <02T10137>. Mn(II)-azido networks of the type [Mn(N3)2(L)] like 13 with new 3-D topologies were obtained using both pyridazine and pyrimidine ligands <02CC64>. 

Nevertheless, direct chlorinations are also known. 3,6-Dichloro-pyridazine can be converted by means of PCI 5 into 3,4,5,6-tetra-chloropyridazine. In 5,6-(or 4,6-)dichloro-2-phenyl-3(2. I)-pyTid-azinone chlorine enters position 4 or 5, and chlorination of molten 2,6-dimethyl-3(2 I)-pyridazinone gives four substances, two of which were identified as its 5-chloro- and 4,5-dichloro derivatives. l-Methyl-2-phenyl-3,6-pyridazinedione (68) adds bromine or chlorine... 

Evidence that nucleophilic substitution of pyridazines may occur also via the hetaryne mechanism has been presented in the case of l-methyl-2-phenyl-4-chloro-(or bromo-)3,6-pyridazinedione which, when treated with piperidine, yielded the 4- and 5-piperidino isomers. Formation of the 5-methoxy isomer as the sole product from the above 4-chloro compound can be interpreted also in terms of an intermediate hetaryne formation. 

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