Organocatalyzed synthesis of chiral non-racemic 1,4-dihydropyridazines

I2-Promoted [4 + 2] cycloaddition of in situ generated azoalkenes with enaminones: facile and efficient synthesis of 1,4-dihydropyridazines and pyridazines

A facile and efficient strategy for the synthesis of 1,4-dihydropyridazines and pyridazines through I2-promoted [4 + 2] cycloaddition of in situ generated azoalkenes with enaminones has been developed. The switch in selectivity is attributed to the judicious choice of different reaction temperatures. The key features of this work include controllable and selective synthesis, good functional group tolerance, good to excellent reaction yields, metal/base-free conditions, and also applicability to one-pot methodology.

Enantioselective synthesis of multi-nitrogen-containing heterocycles using azoalkenes as key intermediates

Chiral multi-nitrogen-containing heterocycles, such as pyrazole, imidazole and pyridazine, are widely found in naturally occurring organic compounds and pharmaceuticals, and hence, their stereoselective and efficient synthesis is an important issue in organic synthesis. Out of the variety of methods that have been developed over the past century, the catalytic asymmetric cyclization and cycloaddition reactions are recognized as the most synthetically useful strategies due to their step-, atom- and redox-economic nature. In particular, the recently developed annulation reactions using azoalkenes as key intermediates show their great ability to construct diverse types of multi-nitrogen-containing heterocycles. In this feature article, we critically analyse the strategic development and the efficient transformation of azoalkenes to chiral heterocycles and α-functionalized ketone derivatives since 2010. The plausible mechanism for each reaction model is also discussed.

Core-Scaffold-Inspired Asymmetric Synthesis of Polysubstituted Chiral Hexahydropyridazines that Potently Inhibit Breast Cancer Cell Proliferation by Inducing Apoptosis

The highly enantioselective preparation of pharmacologically interesting hexahydropyridazine derivatives based on a multicomponent cascade reaction is described. This one-pot approach utilizes an organocatalytic Michael reaction followed by intermolecular α-amination and intramolecular hemiaminalization to yield a chiral pyridazine backbone with contiguous stereogenic centers and multiple functional groups in good yield and with high stereoselectivity. Compounds synthesized by this method potently inhibited proliferation of MCF-7 breast cancer cells. Mechanistic studies suggest that compound 5 c exerts these anticancer effects by inducing apoptosis through extracellular signal related kinase (ERK)- and poly(adenosine diphosphate ribose) polymerase (PARP)-regulated pathways, as well as mitochondrial pathways.

Molecular iodine catalysed domino cyclization in aqueous medium: a simple and efficient synthetic route to 1,4-dihydropyridazines

An efficient protocol has been developed for the synthesis of dihydropyridazines using molecular iodine as green catalyst.

Uncatalyzed one-pot synthesis of highly substituted pyridazines and pyrazoline-spirooxindoles via domino SN/condensation/aza-ene addition cyclization reaction sequence

A previously unknown class of highly substituted pyridazines and pyrazoline-spirooxinoles are easily prepared by an uncatalyzed one-pot three-component approach incorporating a domino SN/condensation/aza-ene addition cyclization reaction sequence. 1,1-Dihydrazino-2-nitroethylene (DHNE) which is generated in situ from the nucleophilic substitution (SN) reaction of hydrazine and 1,1-bis(methylthio)-2-nitroethylene (BMTNE), allowed to be condensed with active 1,2-dicarbonyl compounds followed by an intramolecular aza-ene addition cyclization to obtain the titled products depending on the type of 1,2-dicarbonyl. All reactions are easily performed and proceed with high efficiency under very simple and mild conditions without any catalyst and give good yields avoiding time-consuming, costly syntheses, and tedious workup and purification of products.