Synthesis of Polyhydroxylated Pyrano‐Pyrrole Derivatives from Carbohydrate Precursors

Abstract

The efficient synthesis of novel polyhydroxy‐tetrahydropyrano‐pyrroles from acetylenic carbohydrate precursors in three to four steps is described. The methodology involves, as key steps, the ring contraction of pyridazine intermediates obtained by an inverse‐demand Diels–Alder reaction and subsequent intramolecular lactonization. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Synthesis of Some Novel Norbornene‐Fused Pyridazines as Potent Inhibitors of Carbonic Anhydrase and Acetylcholinesterase

“…Several compounds derived from pyridazines scaffold have been reported to possess a wide spectrum of biological activity such as the antidepressant, dopaminergic drug, monoamine oxidase inhibitor, anticonvulsant, GABA antagonist, muscarinic M1 partial agonist, and acetylcholinesterase (AChE) inhibitor . The chemistry of pyridazines is also dominantly useful as a pioneer for the preparation of other heterocycles, pi‐conjugated organic materials, and self‐assembled supramolecular architectures . Furthermore, two nitrogen atoms offer unique chemical and physicochemical properties such as the properties of conducting electricity, the most elevated dipolar moment, forming H‐bond interactions, coordination with metals, increasing the water solubility, and formation of crystalline for pyridazines .…”

Synthesis of an Oxazole–Pyrrole–Piperazine Scaffold as an α‐Helix Mimetic

“…This synthetic transformation usually gives the expected pyrrole in yields ranging from 27 to 70 %. [15,16] Starting from pyridazine 3a, pyrrole 9 could be obtained in 50 % yield by using an excess amount of zinc in acetic acid. We intended to introduce the piperazine moiety by a standard peptide coupling from the Scheme 1.…”

“…By using the usual conditions with an excess amount of zinc in acetic acid, we obtained desired compounds 17a-d in only 12-29 % yields; these are lower than what was observed previously. [15,16] Final removal of the Boc protecting group of compounds 17a-d was performed with TFA in CH 2 Cl 2 to afford cleanly the desired α-helix mimetics 1a-d in high yields.…”

A convenient synthesis and preparation of the derivatives of ethyl-6-(8-hydroxyquinolin-5-yl)-3-methylpyridazine-4-carboxylate as antimicrobial agents

“…The synthesis of the target compounds 16-21 is depicted in Scheme 4, in which the starting compound 6-(8-hydroxyquinolin-5-yl)-3-methylpyridazine-4-carbohydrazide (8) was allowed to react with ethyl acetoacetate in ethanol to produce the pyrazolinone derivative (16). Condensing of compound 8 with acetyl acetone in glacial acetic acid gave rise to the corresponding (3,5-dimethyl-1H-pyrazol-1-yl)[6-(8-hydroxy quinolin-5-yl)3-methylpyridazin-4-yl]methanone (17).…”

“…A substantial number of pyridazines have been reported to possess and are often employed as potent analgesic [5], antimicrobial [6,7], anti-inflammatory [8], antioxidant [9], antiplatelet [10], anticancer [11], anticonvulsant [12], antifeedant [13], antihypertensive [14], and antidiabetic [15]. Moreover, pyridazines are useful intermediates in the construction of several other heterocycles [16,17]. With all the above facts in mind and as a part of our program directed towards the synthesis of polyfunctionalized substituted 5-heterocyclo-8-hydroxyquinolines of potential biologically interest [18][19][20][21][22], we have devoted some efforts to the construction of a novel ethyl 6-(8-hydroxy quinolin-5-yl)-3-methylpyridazin-4-carboxylate (4) as a conveniently accessible precursor for the synthesis of some hitherto unreported substituted 8-quinolinolinyl-5-pyridazines and their related derivatives in one-pot three component environ-mental friendly method [23].…”