Pyrrolo pyridazine-5,7-dione

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... 

Reaction of 3-alkylamino-6,8-dimethylpyrimido[4,5-c]pyridazin-5,7-diones 80 with cyclohexyl and cycloheptylamines afforded novel cycloalkano bis(pyrrolo[2,3-c]pyrimido[5,4-e]pyridazines 81 <06T652>. 

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>. 

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>. 

Alternatively, pyrrolo[3,4-d]pyrimidine-2,5-diones and pyrimido[4,5-d]pyridazine-2,5-diones have been synthesized by using the same pyrimidine resin precursor, which was first treated with a representative set of primary amines or hydrazines, respectively, to substitute the chlorine. Subsequent cyclative cleavage was performed as already described, leading to the corresponding bicyclic scaffolds in high purity but moderate yield. 

The synthesis of the ultra highly electron-deficient pyrrolo[3,4-inverse-electron-demand DA reaction of the pyrrole-2,5-dione 50 with furyl- or thienyl-decorated tetrazine 51 was applied for preparation of new electrochromic materials with good optical contrast, fast-switching speed, and high coloration efficiency (140L6386). 

One-pot Synthesis of Pyrrolo[3,2-(7]pyridazines and Pyrrole-2,3-diones via Zirconocene-mediated Four-component Coupling of Si-tethered Diyne, Nitriles and Azide. 

One-Pot Synthesis of Pyrrolo[3,2-d]pyridazines and Pyrrole-2,3-Diones via Zirconocene-Mediated Four-Component Coupling of Bis(alkynyl)silane,... 

Pyrrolo[3,2-df pyridazines are a class of interesting and useful A -heterocycles [40—42]. However, synthetic methods for such heterocyclic compounds have been very much limited such as condensation of pyrrole-2,3-diones with hydrazine. There are no reports on one-pot multi-component synthesis of pyrrolo[3,2-(f py-ridazines [43]. Moreover, synthetic methods for pyrrole-2,3-diones are also very limited [43]. On the other hand, transition-metal-mediated reactions of azides are of great importance and versatility in organic synthesis, because azides could be readily transformed into a wide variety of valuable A -containing natural products and medicinal agents [44-50]. 

Based on the mechanistic investigation and chemistry of reactive intermediates in zirconocene-mediated reactions, the author subjected organic azide to the reaction and developed a one-pot synthesis of pyrrolo[3,2-if]pyridazine derivatives via zirconocene-mediated cyclization of one bis(alkynyl)silane, two nitriles, and one azide. When TMSN3 was used as a special azide, pyrrole-2,3-diones were isolated in high yields. These functionalized pyrrole-2,3-diones could be eflhciently further transformed into pyrrole-fused heterocycles (Scheme 2.13). 

Formation of Pyrrolo[3,2-d]pyridazines 2-27 from Pyrrole-2,3-diones 2-24 and Hydrazine Hydrate. A General Procedure for Preparation of 2,4-diisopropyl-3,7-diphenyl- lff-pyrrolo[3,2- f pyridazine (2-27a) In a 20-mL Schlenk tube, hydrazine hydrate (1.0 mmol, 0.057 mL) was added to the ethanol solution (5 mL) of compound 2-24 (180 mg, 0.5 mmol). After the reaction mixture was refluxed for 12 h, the solvent was evaporated in vacuo to give a yellow solid, which was subjected to Si02 column using petroleum ether, ethyl acetate, and triethylamine (100 30 1) as the eluent to give product 2-27a. 

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