Pyridazine tetrahydro

Pyridazine, perfluoro-3,5-diisopropyl-photolysis, 7, 283 Pyridazine, tetrachloro-nucleophilic substitution, 3, 26 Pyridazine, tetrafluoro-nucleophilic substitution, 3, 26 Pyridazine, tetrahydro-, 3, 39-Uo Pyridazine, 3,4,5,6-tetrahydro-... 

Pyridazine, 4-diazo-5,6-dioxo-1 -phenyl-1,4,5,6-tetrahydro-rearrangement, 3, 10 Pyridazine, 4,5-di-S-butyl-perfluoro... 

Pyrimido[4,5-c]pyridazine-5,7-dione, 1,5,6,7-tetrahydro-1,6-dimethyl-applications, 3, 367... 

H,3H- Pyrrolo[l, 2-c]oxazole-l, 3-dione, 5,6,7,8-tetrahydro-IR spectra, 6, 978 [2.2](2,5)Pyrrolophane, N-aryl-rearrangements, 4, 209 Pyrrolophanes natural products, 7, 764 synthesis, 7, 771 Pyrrolophanes, N-aryl-synthesis, 7, 774 (2,4)Pyrrolophanes synthesis, 7, 771 Pyrrolo[3,4-c]pyran-4-ones synthesis, 4, 288 Pyrrolopyrans synthesis, 4, 525, 526 Pyrrolopyrazines synthesis, 4, 526 Pyrrolo[l, 2-a]pyrazines synthesis, 4, 516 Pyrrolo[2,3-6]pyrazines Mannich reaction, 4, 504 Vilsmeier reaction, 4, 505 Pyrrolo[3,4-c]pyrazole, 1,3a,6,6a-tetrahydro-structure, 6, 976 synthesis, 6, 1019 Pyrrolopyrazoles synthesis, 5, 164 Pyrrolo[l,2-6]pyrazoles synthesis, 6, 1002, 1006 Pyrrolo[3,4-c]pyrazoles reactions, 6, 1034 synthesis, 6, 989, 1043 Pyrrolo[3,4-c]pyrazolones synthesis, 6, 989 Pyrfolopyridazines synthesis, 4, 517 Pyrrolo[l, 2-6]pyridazines synthesis, 4, 297 6/7-Pyrrolo[2,3-d]pyridazines synthesis, 4, 291 2/f-Pyrrolo[3,4-d]pyridazines synthesis, 4, 291 6/7-Pyrrolo[3,4-d]pyridazines synthesis, 4, 291... 

Die Reduzierbarkeit cyclischer Hydrazone mit Hydriden ist stark strukturabhangig. 7,8-Dihydro-( 1,3,4-triazolo-[4,3-b]-pyridazin) (I) und auch l,3,4-Triazolo-[4,3-b ]-pyridazin (II) werden durch 10 Mol-Aquiva-lente Natriumboranat in siedendem Athanol mit guten Ausbeuten unter Sattigung des Pyridazin-Rings zu 5,6,7,8-Tetrahydro- (1,3,4-triazolo-[4,3-b]-pyridazin) reduziert2 ... 

Partial saturation of the pyridazino ring of 3-acylamino-4//-pyrimido[l,2-A pyridazin-4-ones and the pyrazino ring of 3-acylamino-4//-pyrazino[l,2-tf]pyrimidin-4-ones in EtOH/AcOH system using Pd/C catalyst, resulted in the respective 6,7,8,9-tetrahydro derivatives in good yields <2000JHC783>. 

The linearly condensed pyridazino[6,l-A]quinazolines can be synthesized by tandem [6+0 (a)] cyclizations, forming the pyrimidine and the pyridazine rings in the same step. Thus, 1,2,3,4-tetrahydro-10//-pyridazino[6, l+]quinazolin-2,10-dione 108 was prepared by thermal cyclization of 106 or 107 (Scheme 12) <1999RJ0286, 1998RJ0534>. Heating/ra r-2-amino-l-cyclohexanecarbohydrazide with 3-(/>-chlorobenzoyl) propionic acid in toluene, the appropriate 2-(/<-chlorophenyl)-3,4,5 ,6,7,8,9,9 -octahydro-10//-pyridazino[6,l- ]quinazolin-10-one was prepared in 35% yield <1998JHC201>. 

The electroreductive hydrogenation of pyridazine-3-ones performed at the first wave, in acidic or basic medium, takes place at the 4,5-double bond. A further reduction of 4,5- dihydropyridazin-3-ones in basic media, affords the corresponding tetrahydro derivatives (Scheme 139) [252]. 

Reduction of 2-methyl-4-phenyl-3//-pyrido[l,2-Z)]pyridazin-3-one (44) with NaBH4 in ethanol afforded the 5,6,7,8-tetrahydro derivative [76JCS(CC)275 78JOC2892],... 

Dehydrogenation of ethyl 2-methyl-4-hydroxy-5,6,7,8-tetrahydro-4a//-pyrido]l,2-/j]pyridazine-3-carboxylate with mercury(II) acetate in ethanol at 45-50°C or over PtOa in boiling ethanol afforded anhydro 3-ethoxycar-bonyl-2-methyl-4-hydroxy-5,6,7,8-tetrahydropyrido[l,2-h]pyridazinium hydroxide (48) (71CPB159). The last compound could be reduced to the starting tetrahydropyrido[l,2-h]pyridazine over Pt02 in ethanol under hydrogen. 

Dimethyl dihydrogen 5,6,7,8-tetrahydro-4a//-pyrido[l, 2-h]pyridazine-5,6,7,8-tetracarboxylate was reacted with diazomethane to give the tetraes-ter (63T1237). 

Photolysis of the zwitterionic pyrido[l,2-h]pyridazines (89) and their 5,6-benzo and 2,3-tetramethylene derivatives afforded 6,7,8,9-tetrahydro-4//-pyrido[l,2-fl]pyrimidin-4-ones (90) and their 8,9-benzo [77H(8)377] and 2,3-tetramethylene derivatives (75JOC2201). Photoinduced ring transformation of 2-phenylpyrido[l,2-fe]pyridazinium-4-olate (73) was investigated in methanol (94T4699). 

Bischler-Napieralski cyclization of pyridazin-6-one 134 with POCI3, and subsequent hydrogenation of the cyclized product 135 over Pt02, gave rise to 2,3,4,6,7,llZ -hexahydro-l//-pyridazino[6,l-fl]isoquinoline (51) (75CPB3056). Treatment of Reissert compound 136 with NaH gave 116-cyano-l, 2,3,116-tetrahydro-4//-pyrido[2,l-fl]phthalazin-4-one (137) (80JHC433). 

The reaction of 2-phenyl-5(4//)-oxazolone (150) and 3-[( )-2-N,N-dimethylaminoethenyljpyridazine (149) in boiling acetic acid afforded 7-benzamido-8//-pyrido[l,2-b]pyridazin-8-one (151) (91BSB533). Treatment of dianion 152 with 1,4-dichlorobutane at -78°C gave 7,llh-diphenyl-2,3,4,llh-tetrahydro-l//-pyrido[2,l-fl]phthalazine (153) (86JHC13). 

The potential tautomerism of l,2,3,4-tetrahydro-5,7-dimethyl-6//-pyrrolo[3,4-i/ pyridazine-l,4-diones has been examined by AMI semi-empirical methods <1998JMT(434)7, 1998JMT(427)65, 1998JMT(430)85>. 

Ring transformation of ethyl 2,4-dioxo-l,2,3,4-tetrahydropyrido[2,3- pyrimidine-5-carboxylates 317 with 80% hydrazine hydrate in boiling ethanol gave a mixture of 5-methyl/allyl/benzylamino-l,2,3,4-tetrahydro-l,4-dioxopyr-ido[3,4-i/ pyridazines 318, pyrido[2,3,4-< <7]pyridazino[3,4-/ [l,2,4]triazepines 319, and a low yield of 2,3,4,6,7-penta-azaphenalene 320. The reaction of 317 with hydrazine hydrate was also performed without a solvent in an oil bath at 125 °C for 1 h to give the same products, but higher yields of 318 and lower yield of 319 as well as traces of 320 were obtained (Equation 25) <1997FA657>. 

Auch durch Retro-Diels-Alder-Reaktion konnen Azoalkane erhalten werden. Die ther-mische Zersetzung von 1,2,3,6-Tetrahydro-pyridazin liefert vorzugsweise cis-Dimethyl-di-azen, wahrend das 2,3-Dimethyl- uberwiegend in trans-Dimethyl-diazen zerfallt. Zur stereochemischen Begriindung hierfiir s.Lit.3. 

Dioxo-l, 23,6-tetrahydro- [pyrazolo-3, 44,5-pyridazin] -5-carbonyl azide 5 D1406... 

Reduction of tetrazolo[ 1,5- >]pyridazine (274) by sodium borohydride results in the partial reduction of the pyridazine moiety (tetrahydro compound 275 was formed) (76JHC835). The catalytic reduction of the substituted tetrazolo[ 1,5- >]pyrimidine (276) afforded the diaminopyrimidine derivative (277) (85MIP155606). 

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