Pyridazines, azido

When chloro compounds are treated with sodium azide in ethanol or aqueous acetone the corresponding azides or tetrazolo[l,5-6]pyridazines are obtained. For example, 3-azido-and 4-azido-pyridazine 1-oxides are obtained from the corresponding chloro compounds ... 

The reactivity of halogens in pyridazine N- oxides towards nucleophilic substitution is in the order 5 > 3 > 6 > 4. This is supported by kinetic studies of the reaction between the corresponding chloropyridazine 1-oxides and piperidine. In general, the chlorine atoms in pyridazine A-oxides undergo replacement with alkoxy, aryloxy, piperidino, hydrazino, azido, hydroxylamino, mercapto, alkylmercapto, methylsulfonyl and other groups. 

When 6-amino-3-chloropyridazine 1-oxide is diazotized in 50% sulfuric acid, 6-hydroxy-3-pyridazinediazonium anhydro salt is formed. An azido group at either position in pyridazine A-oxides can readily be replaced with sodium alkoxides. 

Pyridazine, 4-amino-5-formyl-3,6-dimorpholino-synthesis, 3, 346 Pyridazine, 4-amino-3-halo-reaction with potassium amide, 3, 29 Pyridazine, aryl-synthesis, 3, 28 Pyridazine, arylthio-synthesis, 3, 27 Pyridazine, 3-azido-... 

Because of the presence of two azide groups in positions adjacent to the ring nitrogen atoms in compound 13a, valence bond isomerization can result in formation of 6-azido-7-methyltetrazolo[l,5-A pyridazine 14a, 6-azido-8-methyltetrazolo[l,5-A pyridazine 15a, and the bis-tetrazole compound 16a. Calculations have been carried out by using hybrid density functional theory (B3LYP/6-311+G(d,p)) and complete basis set treatments (CBS-4M). All calculations revealed that the 8-methyl derivative 15a is the most stable isomer. Similar studies on the triazide derivative 13b, however, indicated that in this case the equilibrium is shifted to the 7-methyl form 14b. All these conclusions proved to be in entire agreement with the experimental findings (see Section 11.18.3.2.). 

Bromination of 1114 gave l-(3-bromo-2-oxopropyl)pyridazin-6-ones (1116) as a major product in addition to 1115 (91JHC385). Reaction of 1116 with sodium azide gave the corresponding l-(3-azido-2-oxopropyl)-pyridazin-6-ones 1117, which was reduced to 1118. 4,5-Dichloro-l-(2,3-dihydroxypropyl)pyridazin-6-one 1121 was also prepared from 1116 via 1119 and the corresponding 2,3-epoxypropyl derivative 1120 (91JHC1235). 

Man erhalt so aus der entsprechenden C-Azido-Verbindung z. B. 6-Amino- ( 100%) und 6-Amino-7,8-dimethyl [Pg.1133]

One final interesting preparation of this ring system involves the reaction of the tetrazolo[l,5-6]pyridazine (174) with polyphosphoric acid to give 7-azido-4H-pyrimido[l,2-6]pyridazin-4-one (175). This reaction involves azido-tetrazolo valence isomerization, which has been studied in other heterocyclic systems (71JHC1055). 

The 3-chloro-l,7-dimethylpyridazino[3,4-(7][l,3]oxazine-4,5-dione (149) was prepared in a four-step synthesis starting with (Z)-methyl-3-(3,6-dichloro-l-methyl-4-oxo-l,4-dihydropyridazin-5-yl)-2-methylacrylate (146) which is converted with sodium azide into the 6-azido compound (147). Heating in o-dichlorobenzene at 150°C results in cyclization to methyl 3-chloro-l,6-dimethyl-4-oxo-1,4-dihydro(7//)pyrrolo[2,3-c]pyridazine-5-carboxylate (148) via a nitrene intermediate. Ozonolysis effects ring-enlargement of the pyrrole ring into the 3-chloro-l,7-dimethylpyridazino[3,4-d][l,3]oxazine-4,5-dione (149) (Scheme 26) <79JHC1213>. 

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>. 

There are individual cases of replacement of other groups in substituted pyridazine iV-oxides, such as the substitution of methoxy or ethoxy groups with amino or hydrazino groups, and replacement of an azido group with a methoxy, ethoxy, or benzyloxy group... 

Phenol 2-Azido- X/3, 808 Pyridazine 4-Cyan-3-hydroxy-5(or6)-methyl- E9a, 587 (H3C-CO-CHO + NC-CH2-COOR)... 

Ethan 1-Azido-l-methoxy-l-phenyl-E14a/2, 290 (Enol-ether/HN3), 118 (Keton + HN3/0,0-Acetal) Pyridazine 4-(l-Formyl-pyrrolidin-2-yl)- E9a, 624 (H - l-CHO-2-pyrrolidinyl)... 

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