Generation of multimillion chemical space based on the parallel Groebke–Blackburn–Bienaymé reaction

• Evgen V. Govor,
• Vasyl Naumchyk,
• Ihor Nestorak,
• Dmytro S. Radchenko,
• Dmytro Dudenko,
• Yurii S. Moroz,
• Olexiy D. Kachkovsky and
• Oleksandr O. Grygorenko

Beilstein J. Org. Chem. 2024, 20, 1604–1613, doi:10.3762/bjoc.20.143

• wide range of aminopyridines, pyrazines, and pyridazines, it worked poorly for aminoazoles, aminopyrimidines, substrates with strong electron-withdrawing groups, and substrates bearing additional dialkylamino or alkoxy substituents. The electronic nature was a major limiting factor for other two

Synthesis of spiropyridazine-benzosultams by the [4 + 2] annulation reaction of 3-substituted benzoisothiazole 1,1-dioxides with 1,2-diaza-1,3-dienes

• Wenqing Hao,
• Long Wang,
• Jinlei Zhang,
• Dawei Teng and
• Guorui Cao

Beilstein J. Org. Chem. 2024, 20, 280–286, doi:10.3762/bjoc.20.29

• . Inspired by the potential biological activity of pyridazines and in continuation of our work on the synthesis of spirobenzosultams [31][32][33], we herein report a highly diastereoselective route for the synthesis of spiropyridazine-benzosultams through [4 + 2] annulation reactions of 3-substituted

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• Ramazan Kocak Arif Dastan Department of Chemistry, Faculty of Sciences, Atatürk University, Erzurum, 25240, Turkey 10.3762/bjoc.17.61 Abstract The synthesis of novel polycyclic π-conjugated dihydropyridazines, pyridazines, and pyrroles was studied. Dihydropyridazine dyes were synthesized by

• inverse electron-demand Diels–Alder cycloaddition reactions between a dibenzosuberenone and tetrazines that bear various substituents. The pyridazines were synthesized in high yields by oxidation of dihydropyridazine-appended dibenzosuberenones with PIFA or NO. p-Quinone derivatives of pyridazines were

• also obtained by H-shift isomerization following the inverse electron-demand Diels–Alder reaction of tetrazines with p-quinone dibenzosuberenone. Then these pyridazines were converted to the corresponding pyrroles by reductive treatment with zinc. It was observed that all the dihydropyridazines

Hydrazides in the reaction with hydroxypyrrolines: less nucleophilicity – more diversity

• Dmitrii A. Shabalin,
• Evgeniya E. Ivanova,
• Igor A. Ushakov,
• Elena Yu. Schmidt and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2021, 17, 319–324, doi:10.3762/bjoc.17.29

• , namely a Brønsted acid-activated hydroxypyrroline, depend on the reaction conditions and the structure of the hydrazides. Keywords: hydrazides; pyridazines; pyrrolines; recyclization; ring expansion; Introduction Di- and tetrahydropyridazines are valuable heterocyclic motifs which are utilized as key

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• state quencher, as well as by the lowered rate of the reaction in the presence of the triplet energy quencher 2,5-dimethylhexa-2,4-diene or pyridazines, additives with lower triplet state energies than 4-anisaldehyde (52). The fact that the solvent polarity did not affect the sensitivity of the process

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• hydroxamic moieties [13][14][15], the non-availability of the central core modification stimulated our interest toward altering the central core to evaluate efficacy. We found particular interest in the replacement of the phenyl ring with diazine cores (pyridazines, pyrimidines and pyrazines) as their

Mechanistic studies of an L-proline-catalyzed pyridazine formation involving a Diels–Alder reaction with inverse electron demand

• Anne Schnell,
• J. Alexander Willms,
• S. Nozinovic and
• Marianne Engeser

Beilstein J. Org. Chem. 2019, 15, 30–43, doi:10.3762/bjoc.15.3

• between ketones and aryl-substituted 1,2,4,5-tetrazines which leads to functionalized pyridazines. They also postulated a mechanism (Scheme 1) for the reaction [51]. Based on the knowledge that secondary amines catalyze the formation of enamines from ketones and other carbonyl compounds [33], an initial

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• oxidant (Scheme 22) [67]. Heterocycles in drugs are not only restricted to five-membered rings. Pyridines, pyrazines, pyrimidines, pyridazines are all common functional groups in biologically active compounds. Liu et al. have published the visible light-catalysed oxidation of dihydropyrimidines (DHPMs

A novel synthetic approach to hydroimidazo[1,5-b]pyridazines by the recyclization of itaconimides and HPLC–HRMS monitoring of the reaction pathway

• Dmitry Yu. Vandyshev,
• Khidmet S. Shikhaliev,
• Andrey Yu. Potapov,
• Michael Yu. Krysin,
• Fedor I. Zubkov and
• Lyudmila V. Sapronova

Beilstein J. Org. Chem. 2017, 13, 2561–2568, doi:10.3762/bjoc.13.252

• University, Miklukho-Maklaya St., 6, Moscow 117198, Russian Federation 10.3762/bjoc.13.252 Abstract The novel cascade two-stage reaction between itaconimides and 1,2-diamino-4-phenylimidazole proceeds regio- and chemoselectively to form tetrahydroimidazo[1,5-b]pyridazines and includes nucleophilic C

• -addition by the activated C=C double bond and subsequent intramolecular recyclization of the intermediate with the amino group involved. Keywords: cascade reaction; diaminoimidazoles; HPLC–HRESIMS; imidazo[1,5-b]pyridazines; itaconimides; Introduction Among the numerous bicyclic fused imidazole

• ], antitumor agents [9], and are stimulators of guanylate cyclase [10], whereas imidazo[1,5-c]pyrimidines demonstrate anti-infectious effects in the treatment of brucellosis [11], etc. However, the chemistry, medicinal chemistry and pharmacology of imidazo[1,5-b]pyridazines, with the imidazole ring connected

Preparation of imidazo[1,2-a]-N-heterocyclic derivatives with gem-difluorinated side chains

• Layal Hariss,
• Kamal Bou Hadir,
• Mirvat El-Masri,
• Thierry Roisnel,
• René Grée and
• Ali Hachem

Beilstein J. Org. Chem. 2017, 13, 2115–2121, doi:10.3762/bjoc.13.208

• prepared in fair yields by the reaction of gem-difluoroenones with aminopyridines, -pyrimidines and -pyridazines. Condensed heterocycles of this type play an important role as key core structures of various bioactive compounds. Further, starting with a chloroimidazopyridazine derivative, Pd-catalyzed

• [1,2-a]pyrimidines 7d and imidazo[1,2-b]pyridazines 7e, have been synthesized by the same method albeit in slightly decreased yields (Table 2, entries 4 and 5). The structures of molecules 7 are in full agreement with their spectroscopical (NMR) and analytical data (HRMS). For the imidazopyridines, the

An overview of the synthetic routes to the best selling drugs containing 6-membered heterocycles

• Marcus Baumann and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2013, 9, 2265–2319, doi:10.3762/bjoc.9.265

• Dihydropyridines and piperidines Pyrimidines and quinazolines Pyrazines and piperazines Pyridazines and perhydropyridazines Triazines and polyazacyclic systems Synthetic chemistry can rightfully be considered a prerequisite of our modern society [1]. This discipline supplies many valuable resources to our world

• , pyrimidine-derived analogues (1,3-diazines) are the most common. Pyridazines (1,2-diazines) and pyrazines (1,4-diazines) are less prominent. The main reasons are most probably that pyrimidines are highly abundant in important biogenic molecules such as the ribonucleotides and that this heterocycle can be

Synthesis and quantitative structure–activity relationship study of substituted imidazophosphor ester based tetrazolo[1,5-b]pyridazines as antinociceptive/anti-inflammatory agents

• Wafaa M. Abdou,
• Neven A. Ganoub and
• Eman Sabry

Beilstein J. Org. Chem. 2013, 9, 1730–1736, doi:10.3762/bjoc.9.199

• Wafaa M. Abdou Neven A. Ganoub Eman Sabry Chemical Industries Division, National Research Centre, Elbohouth St. D-12311, Dokki, Cairo, Egypt. Fax: 202 7601877 10.3762/bjoc.9.199 Abstract A high-yielding general synthesis of imidazophosphor ester based tetrazolo[1,5-b]pyridazines is described. A

• -inflammation properties of the new tetrazolo[1,5-b]pyridazines-bearing mono- (4, 7, 10a, 10b, 13, 17, 19) and diphosphonate nuclei (15) were evaluated in an animal model, by the carrageenan–induced paw edema (CPE) method. Following the standard procedures [34][35], these compounds were administered

A simple, enaminone-based approach to some bicyclic pyridazinium tetrafluoroborates

• František Josefík,
• Markéta Svobodová,
• Valerio Bertolasi and
• Petr Šimůnek

Beilstein J. Org. Chem. 2013, 9, 1463–1471, doi:10.3762/bjoc.9.166

• this, reactions of enaminones with diazonium salts giving substituted pyridazines are also described [25][26][27][28]. Our method does not require any additive, and the transformation from 1 to 2 is performed as a one-pot procedure. Different substrates are used and different and novel pyridazinium

Camera-enabled techniques for organic synthesis

• Steven V. Ley,
• Richard J. Ingham,
• Matthew O’Brien and
• Duncan L. Browne

Beilstein J. Org. Chem. 2013, 9, 1051–1072, doi:10.3762/bjoc.9.118

• ]. The route required a significant quantity of an orthogonally protected piperazic acid (Figure 10). This was achieved using a new enantioselective organocatalytic protocol with a tetrazole organocatalyst, which afforded dihydro pyridazines from achiral aldehydes [61][62]. Unfortunately, while this

9,10-Dioxa-1,2-diaza-anthracene derivatives from tetrafluoropyridazine

• Graham Pattison,
• Graham Sandford,
• Dmitrii S. Yufit,
• Judith A. K. Howard,
• John A. Christopher and
• David D. Miller

Beilstein J. Org. Chem. 2010, 6, No. 45, doi:10.3762/bjoc.6.45

• ]dioxino[2,3-c]pyridazine also referred to as benzodioxinopyridazine) systems are very rare heterocyclic structures and only a handful of analogues based upon this molecular skeleton have been synthesised, mainly by the reaction of chlorinated pyridazines with catechol [14][15][16]. In this paper, we

An expedient and new synthesis of pyrrolo[1,2-b]pyridazine derivatives

• Rajeshwar Reddy Sagyam,
• Ravinder Buchikonda,
• Jaya Prakash Pitta,
• Himabindu Vurimidi,
• Pratap Reddy Padi and
• Mahesh Reddy Ghanta

Beilstein J. Org. Chem. 2009, 5, No. 66, doi:10.3762/bjoc.5.66

• ]pyridazines through a hitherto unprecedented approach from a BOC-protected 1-aminopyrrole derivative and α,β-unsaturated ketones. Results and Discussion 2-[2-(4-Fluorophenyl)-2-oxo-1-phenylethyl]-4-methyl-3-oxo-pentanoic acid phenylamide 1 was reacted with tertiary butyl carbazate 2 in toluene and cyclohexane

• equiv), toluene (30.0 volumes). 3,4-Dihydropyrrolo[1,2-b]pyridazines 6a–j. Yields and reaction times for compounds 17a–j. Acknowledgments The authors wish to thank the management of Dr. Reddy’s Laboratories Limited for providing facilities to carry out this work and co-operation extended by all the

The tert- amino effect in heterocyclic chemistry: Synthesis of new fused pyrazolinoquinolizine and 1,4-oxazinopyrazoline derivatives

• Dipak Prajapati and
• Kalyan Jyoti Borah

Beilstein J. Org. Chem. 2007, 3, No. 43, doi:10.1186/1860-5397-3-43

• with at least one heteroatom, such as nitroso,[13] nitro,[14][15] azo,[16] amine,[17] azomethine, [18][19][20] carbonyl, [20][21][22][23] or thiocarbonyl moieties as the ortho substituents.[10] The application of the tert-amino effect to the synthesis of pyrido-fused benzenes, pyridazines and uracils