Synthesis and autoxidation of new tetracyclic 9H,10H-indolizino[1,2-b]indole-1-ones

A single pot organocatalytic diastereoselective synthesis of fluorescent ring fused 2-pyridone decalines via a domino Knoevenagel/Michael/hydro-lactamisation sequence

A highly efficient one-pot triple cascade approach is developed to synthesise fluorescent, fused, octahydro-2-pyridone decalines in good to excellent yields using l-proline/PhCOOH as an organocatalyst.

S29434, a Quinone Reductase 2 Inhibitor: Main Biochemical and Cellular Characterization

Quinone reductase 2 (QR2, E.C. 1.10.5.1) is an enzyme with a feature that has attracted attention for several decades: in standard conditions, instead of recognizing NAD(P)H as an electron donor, it recognizes putative metabolites of NADH, such as N-methyl- and N-ribosyl-dihydronicotinamide. QR2 has been particularly associated with reactive oxygen species and memory, strongly suggesting a link among QR2 (as a possible key element in pro-oxidation), autophagy, and neurodegeneration. In molecular and cellular pharmacology, understanding physiopathological associations can be difficult because of a lack of specific and powerful tools. Here, we present a thorough description of the potent, nanomolar inhibitor [2-(2-methoxy-5H-1,4b,9-triaza(indeno[2,1-a]inden-10-yl)ethyl]-2-furamide (S29434 or NMDPEF; IC₅₀ = 5-16 nM) of QR2 at different organizational levels. We provide full detailed syntheses, describe its cocrystallization with and behavior at QR2 on a millisecond timeline, show that it penetrates cell membranes and inhibits QR2-mediated reactive oxygen species (ROS) production within the 100 nM range, and describe its actions in several in vivo models and lack of actions in various ROS-producing systems. The inhibitor is fairly stable in vivo, penetrates cells, specifically inhibits QR2, and shows activities that suggest a key role for this enzyme in different pathologic conditions, including neurodegenerative diseases.

Reaction of silylallenes with triplet molecular oxygen

A facile formal ene reaction of trisubstituted silylallenes with triplet molecular oxygen involving the cleavage of a C(sp²)–H bond has been described.

Greener synthesis of indolizine analogues using water as a base and solvent: study for larvicidal activity against Anopheles arabiensis

Greener synthesis of a series of novel indolizine analogues have been achieved by the cyclization of aromatic cycloimmonium ylides with electron-deficient alkynes in the presence of water as the base and solvent at 80 °C. Yield of the title compounds was good and reactions performed were eco-friendly. The structures of these newly synthesized compounds have been confirmed by spectroscopic techniques such as FTIR, NMR, LC-MS, and elemental analysis. Characterized title compounds were evaluated for larvicidal activity against Anopheles arabiensis by standard WHO larvicidal assay using Temefos as standard at 4 μg/mL. Title compounds 2e, 2f, and 2g emerged as promising larvicidal agents.

One-pot synthesis of 5H-1,3,4-thiadiazolo[3,2-a]pyrimidin-5-one derivatives

A novel and efficient one-pot method has been developed for the synthesis of 2-substituted-5H-1,3,4-thiadiazolo[3,2-a]pyrimidin-5-one derivatives by the tandem reaction of [3 + 3] cycloaddition, reduction, deamination.

Tandem Michael Addition/Amino-Nitrile Cyclization from 2-Formyl-1,4-DHP in the Synthesis of Novel Dihydroindolizine-Based Compounds

A simple and efficient methodology for the synthesis of a small library of substituted indolizines with different degrees of saturation starting from the racemic 2-formyl-1,4-DHP reagent was described. The large synthetic possibilities of this reagent as well as of its Knoevenagel corresponding 2-dicyanovinyl-1,4-DHP reagent were investigated using four kinds of activated methylenes as nucleophiles. The key step of the sequential reaction was based on the highly diastereoselective tandem Michael addition/intramolecular amino-nitrile cyclization catalyzed by an organic base, which resulted in the formation of 1,7-dihydroindolizines in a diastereoselective manner. The process seems to be a straightforward one and can be extended to numerous active methylenes such as malononitrile, 1,3-diketones, and alkyl acetoacetates. The 1,3-hydrogen shift of partially hydrogenated indolizines was accomplished easily with a base at room temperature, giving rise to the corresponding 7,8-dihydroindolizines in very good yields. Interestingly, when the active methylene bears a leaving group, the latter process could not be accomplished because a rare cis-elimination of phenylsulfinic acid and nitrous acid preceded the hydrogen shift. The resulting 1,7-dihydroindolizines bearing an exo-methylene group at C1 were not isolated in all cases, as they turned rapidly to indolizines as the thermodynamically more stable products. During these investigations, oxidization of 1,7-dihydroindolizines with CuCl(2) resulted in the formation of polysubstituted pyridines. Also, the epimerization of certain 1,7-dihydroindolizines was evidenced in the solution studied by NMR spectroscopy, whereas in the solid state, they existed only in a unique form as shown by X-ray diffraction analysis of a representative structure. Finally, all products reported herein bear a primary amine and a nitrile function crucial for further transformations. These include the introduction of various pharmacophore groups at either NH(2) or CN groups as well as at both groups at the same time to access the more elaborated indolizines fused to N- or N,N-heterocycles.

A Facile Oxidation and Oxygen Insertion of the Cyclopentadiene Ring by Molecular Oxygen in Solution

[reaction: see text] Oxidation of substituted cyclopentadienes by molecular oxygen afforded the corresponding pyrylium cations in acidic solution, whereby an oxygen atom was inserted into the cyclopentadiene ring. This novel one-step reaction proceeds in a different yield depending on substitution patterns of the cyclopentadiene. A possible reaction pathway and formation mechanism of the pyrylium cation are proposed and discussed.

A novel microwave-mediated one-pot synthesis of indolizines via a three-component reaction

[reaction: see text] The microwave-mediated three-component reaction of acyl bromide, pyridine, and acetylene is catalyzed by basic alumina to give corresponding indolizines in excellent yields in a one-pot reaction.