Contributions to syntheses of pyrrolo[2,1-a]phthalazines

Synthesis and Toxicity Evaluation of New Pyrroles Obtained by the Reaction of Activated Alkynes with 1-Methyl-3-(cyanomethyl)benzimidazolium Bromide

A series of new pyrrole derivatives were designed as chemical analogs of the 1,4-dihydropyridines drugs in order to develop future new calcium channel blockers. The new tri- and tetra-substituted N-arylpyrroles were synthesized by the one-pot reaction of 1-methyl-3-cyanomethyl benzimidazolium bromide with substituted alkynes having at least one electron-withdrawing substituent, in 1,2-epoxybutane, acting both as the solvent and reagent to generate the corresponding benzimidazolium N3-ylide. The structural characterization of the new substituted pyrroles was based on IR, NMR spectroscopy as well as on single crystal X-ray analysis. The toxicity of the new compounds was assessed on the plant cell using Triticum aestivum L. species and on the animal cell using Artemia franciscana Kellogg and Daphnia magna Straus crustaceans. The compounds showed minimal phytotoxicity on Triticum rootlets and virtually no acute toxicity on Artemia nauplii, while on Daphnia magna, it induced moderate to high toxicity, similar to nifedipine. Our research indicates that the newly synthetized pyrrole derivatives are promising molecules with biological activity and low acute toxicity.

Microwave Assisted Reactions of Fluorescent Pyrrolodiazine Building Blocks

We report here the synthesis and optical spectral properties of several new pyrrolodiazine derivatives. The luminescent heterocycles were synthesized by 1,3-dipolar cycloaddition reactions between N-alkylated pyridazine and methylpropiolate or dimethyl acetylenedicarboxylate (DMAD). The pyrrolopyridazine derivatives are blue emitters with moderate quantum yields (around 25%) in the case of pyrrolopyridazines and negligible yet measurable emission for pyrrolophthalazines. In a subsequent step towards including the pyrrolodiazine moiety, given its spectral properties in various macromolecular frameworks such as biological molecules, a subset of the synthetized compounds has been subjected to α-bromination. A selective and efficient way for α-bromination in heterogeneous catalysis of pyrrolodiazine derivatives under microwave (MW) irradiation is presented. We report substantially higher yields under MW irradiation, whereas the solvent amounts required are at least five-fold less compared to classical heating.

5,6-Dipropylphthalazino[2,3-a]cinnoline-8,13-dione

In the title compound, C22H22N2O2, the two central fused pyridazine rings have screw-boat conformations and the dihedral angle between their mean planes is 36.22 (8)°. The mean plane of the cinnoline ring system makes a dihedral angle of 46.56 (5)° with the mean plane of the phthalazine ring to which it is fused. In the crystal, molecules are linkedviaC—H...O hydrogen bonds, forming chains along thebaxis. The chains are reinforced by C—H...π interactions.

New highlights of the syntheses of pyrrolo[1,2-a]quinoxalin-4-ones

The one-pot three-component reactions of 1-substituted benzimidazoles with ethyl bromoacetate and electron-deficient alkynes, in 1,2-epoxybutane, gave a variety of pyrrolo[1,2-a]quinoxalin-4-ones and pyrrolo[1,2-a]benzimidazoles. The influence of experimental conditions on the course of reaction was investigated. A novel synthetic pathway starting from benzimidazoles unsubstituted at the five membered ring, alkyl bromoacetates and non-symmetrical electron-deficient alkynes in the molar ratio of 1:2:1, in 1,2-epoxybutane at reflux temperature, led directly to pyrrolo[1,2-a]quinoxalin-4-ones in fair yield by an one-pot three-component reaction.

Synthesis of pyrrolo[2,1-a]isoquinolines by multicomponent 1,3-dipolar cycloaddition

Pyrrolo[2,1-a]isoquinoline derivatives were synthesized by one-pot three-component reactions starting from isoquinoline, 2-bromoacetophenones and different non-symmetrical acetylenic dipolarophiles using 1,2-epoxypropane as solvent. The structure of the compounds was assigned by IR and NMR spectroscopy.

5-Bromophthalazine hemihydrate

The title compound, C₈H₅BrN₂·0.5H₂O, is a phthalazine derivative synthesized from 3-bromo­benzene-1,2-dicarbaldehyde and hydrazine. The mol­ecule is essentially planar, the deviation from the mean plane of the phthalazine ring being 0.015 (3) Å. The O atom of the solvent water mol­ecule is situated on a twofold rotation axis. In the crystal, O—H⋯N hydrogen bonds and short N⋯Br [2.980 (3) Å] contacts lead to the formation of a two-dimensional network parallel to (101).

Efficient one-pot, three-component synthesis of a library of pyrrolo[1,2-c]pyrimidine derivatives

Herein is reported a simple and efficient one-pot three-component synthesis of pyrrolo[1,2-c]pyrimidine derivatives starting from various substituted pyrimidines, 2-bromoacetophenones, and electron deficient alkynes in epoxides acting both as reaction medium and HBr scavanger. This method proved to be very lucrative and avoids formation of ylide inactivation products. The synthesis represents an environmentally benign alternative to classical methods. The new library of compounds was briefly characterized regarding the improved Lipinski rule to asses the potential drug-likeness of the compounds. The majority of compounds are statisfing the Lipinski rule.