Publisher Summary The formation of 1,2,4-triazolo [1,5-a] pyrimidines (TPs) was first reported by Biilow and Haas Over the next 50 years, only a few papers and patents on TPs were published, which were included in Mosby's comprehensive monograph on “Heterocyclic Systems with Bridgehead Nitrogen Atoms” Most syntheses of TPs start either from a 1,2,4-triazole derivative or from a pyrimidine residue and need annulation of a second heterocyclic ring Preferably 5-amino-1,2,4-triazoles (AT) and 2-hydrazinopyrimidines (HP) are used as starting synthons In the synthesis of TPs from HPs, intermediates are believed to exist and have been isolated in many cases These products and other acylated HPs may serve as convenient starting materials for cyclization reactions Acylated HPs are also prepared from 2-alkylthiopyrimidines and acylhydrazines and, further, cyclized in situ to triazolopyrimidines Many TPs have been tested as potential growth inhibitors of microorganisms, because they are isomeric to purines and in some cases can be converted to nucleoside analogs

1,2,4-Triazolo[1,5-a]pyrimidines

Publisher Summary This chapter discusses the synthetic methods for the synthesis of pyridazine. Numerous syntheses of pyridazines follow the well-known approaches, but there are some significant developments and new methods, such as syntheses of pyridazines by cycloaddition, which have become powerful synthetic tools in the hands of organic chemists. Pyridazines have been investigated intensely, from a theoretical standpoint, by spectroscopic methods. Several aspects of pyridazine chemistry and activity are included in this chapter. The chapter deals with aromaticity and antiaromaticity of azines and substituent effects in azines. The chapter covers unusual organic compounds including azoalkanes, cycloadditions of azadienes, diazoquinones, thermal and photochemical decomposition of azoalkanes, and one-electron oxidations. The pyridazine nucleosides, some biologically active pyridazines, antihypertensive 3-hydrazinopyridazines, and pyridazines with antimicrobial activity are also reviewed in the chapter

Advances in Pyridazine Chemistry

1,3-Dipolar cycloadditions of diazoalkanes to some nitrogen containing heteroaromatic systems

Verbindungen der allgemeinen Formel I Compounds of general formula I worin einer der Substituenten R1 und R2 Methoxy, Difluormethoxy oder Ethoxy und der andere C1-C5-Alkoxy, C4-C7-Cycloalkoxy, C3-C7-Cycloalkylmethoxy, C3-C5-Alkenyloxy oder C1-C4-Polyfluoralkoxy und X Cyanamino bedeutet, und ihre pharmakologisch vertraglichen Salze mit Basen sind neu und eignen sich als bronchospasmolytische Wirkstoffe. wherein one of the substituents R1 and R2 denotes methoxy, difluoromethoxy or ethoxy and the other is C1-C5-alkoxy, C4-C7-cycloalkoxy, C3-C7-cycloalkylmethoxy, C3-C5-alkenyloxy or C1-C4-polyfluoroalkoxy and X denotes cyanamino, and their pharmacologically tolerable salts with bases are new and useful as bronchospasmolytic agents.

Arylpyridazines, their preparation, their use and pharmaceuticals containing them

A facile preparation of trans-1,2-cyclopropanes containing p-trifluoromethylphenyl group and its application to the construction of pyrazole and cyclopropane ring fused pyridazinone derivatives

Reactions of N-heteroarylformamide oximes and N-heteroarylacetamide oximes with N,N-dimethylformamide dimethyl acetal. Synthesis of 2-methyl-s-triazolo[1,5-x]azines and N-methylcyanoaminoazines

1,3-dipolar cycloaddition of 2-diazopropane to 2-methyl-6-phenylpyridazin-3(2H)-one. The formation of pyrazolo/3,4-D/pyridazine derivatives

Directed regiospecificity of 1,3-dipolar cycloaddition of 2-diazopropane to 4- and 5-substituted pyridazin-3(2H)-ones

The synthesis and transformations of 9H‐imidazo[1,2‐b]pyrazolo[4,3‐d]‐pyridazine and 9H‐pyrazolo[4,3‐d]‐s‐triazolo[4,3‐b]pyridazine derivatives

1,3-Dipolar cycle-addition of 2-diazoalkanes to pyridazin-3(2H)-one derivatives. The formation of 3H-pyrazolo[3,4-d]pyridazin-4(5H)-one and 3H-pyrazolo[3,4-d]pyridazin-7(6H)-one derivatives

Anton Štimac

Papers

Reactions of N-heteroarylformamide oximes and N-heteroarylacetamide oximes with N,N-dimethylformamide dimethyl acetal. Synthesis of 2-methyl-s-triazolo[1,5-x]azines and N-methylcyanoaminoazines

1,3-dipolar cycloaddition of 2-diazopropane to 2-methyl-6-phenylpyridazin-3(2H)-one. The formation of pyrazolo/3,4-D/pyridazine derivatives

Directed regiospecificity of 1,3-dipolar cycloaddition of 2-diazopropane to 4- and 5-substituted pyridazin-3(2H)-ones

The synthesis and transformations of 9H‐imidazo[1,2‐b]pyrazolo[4,3‐d]‐pyridazine and 9H‐pyrazolo[4,3‐d]‐s‐triazolo[4,3‐b]pyridazine derivatives

1,3-Dipolar cycle-addition of 2-diazoalkanes to pyridazin-3(2H)-one derivatives. The formation of 3H-pyrazolo[3,4-d]pyridazin-4(5H)-one and 3H-pyrazolo[3,4-d]pyridazin-7(6H)-one derivatives