Regioselective Three-component Reaction Research Articles

Synthesis of Tetracyclic Spirooxindolepyrrolidine-Engrafted Hydantoin Scaffolds: Crystallographic Analysis, Molecular Docking Studies and Evaluation of Their Antimicrobial, Anti-Inflammatory and Analgesic Activities

In a sustained search for novel potential drug candidates with multispectrum therapeutic application, a series of novel spirooxindoles was designed and synthesized via regioselective three-component reaction between isatin derivatives, 2-phenylglycine and diverse arylidene-imidazolidine-2,4-diones (Hydantoins). The suggested stereochemistry was ascertained by an X-ray diffraction study and NMR spectroscopy. The resulting tetracyclic heterocycles were screened for their in vitro and in vivo anti-inflammatory and analgesic activity and for their in vitro antimicrobial potency. In vitro antibacterial screening revealed that several derivatives exhibited remarkable growth inhibition against different targeted microorganisms. All tested compounds showed excellent activity against the Micrococccus luteus strain (93.75 µg/mL ≤ MIC ≤ 375 µg/mL) as compared to the reference drug tetracycline (MIC = 500 µg/mL). Compound 4e bearing a p-chlorophenyl group on the pyrrolidine ring exhibited the greatest antifungal potential toward Candida albicans and Candida krusei (MIC values of 23.43 µg/mL and 46.87 µg/mL, respectively) as compared to Amphotericin B (MIC = 31.25 and 62.50 µg/mL, respectively). The target compounds were also tested in vitro against the lipoxygenase-5 (LOX-5) enzyme. Compounds 4i and 4l showed significant inhibitory activity with IC50 = 1.09 mg/mL and IC50 = 1.01 mg/mL, respectively, more potent than the parent drug, diclofenac sodium (IC50 = 1.19 mg/mL). In addition, in vivo evaluation of anti-inflammatory and analgesic activity of these spirooxindoles were assessed through carrageenan-induced paw edema and acetic acid-induced writhing assays, respectively, revealing promising results. In silico molecular docking and predictive ADMET studies for the more active spirocompounds were also carried out.

Regioselective Approach to β-Peroxyl Alcohols and Ethers from Alkenes.

A different regioselective three-component reaction of alkenes, oxygen sources, and hydroperoxides mediated by ammonium iodine to α-oxyperoxidates has been developed. Mechanistic studies demonstrated that regioselective radical addition and subsequent SN2 nucleophilic substitution were possible for the formation of products. In addition to the traditional pathway of SN2 reaction, that is, where nucleophiles attack the α-C atoms at the back side, an additional unusual transition configuration with the H2O molecule attacking the α-C atom at the front side was obtained.

Regioselective Synthesis of 3-Trifluoromethylpyrazole by Coupling of Aldehydes, Sulfonyl Hydrazides, and 2-Bromo-3,3,3-trifluoropropene.

A general and practical strategy for 3-trifluoromethylpyrazole synthesis is reported that occurs by the three-component coupling of environmentally friendly and large-tonnage industrial feedstock 2-bromo-3,3,3-trifluoropropene (BTP), aldehydes, and sulfonyl hydrazides. This highly regioselective three-component reaction is metal-free, catalyst-free, and operationally simple and features mild conditions, a broad substrate scope, high yields, and valuable functional group tolerance. Remarkably, the reactions could be performed on a 100 mmol scale and smoothly afforded the key intermediates for the synthesis of celecoxib, mavacoxib, SC-560, and AS-136A. Preliminary mechanism studies indicated that a 1,3-hydrogen atom transfer process was involved in this transformation.

Synthesis of Functionalized Pyrazin-2(1 H)-ones via Tele-Nucleophilic Substitution of Hydrogen Involving Grignard Reactants and Electrophiles.

The reaction of 6-chloro-1-methylpyrazin-2(1 H)-one with Grignard reactants followed by quenching with different electrophiles gave access to a variety of 3,6-difunctionalized 1-methylpyrazin-2(1 H)-ones. This regioselective three-component reaction represents the first example of a tele-nucleophilic substitution of hydrogen (SNH) in which the anionic σH adduct is quenched by electrophiles (other than a proton) before elimination takes place. Quenching the reaction with iodine (I2) or bromine (Br2) provides an alternative reaction pathway, yielding a 3-functionalized 6-chloro-1-methylpyrazin-2(1 H)-one or 5-bromo-6-chloro-1-methylpyrazin-2(1 H)-one, respectively. The halogens present offer opportunities for further selective transformations.

Regioselective synthesis of pyrimidine-fused tetrahydropyridines and pyridines by microwave-assisted one-pot reaction.

A regioselective three-component reaction of α,β-unsaturated aldehydes, cyclic 1,3-dicarbonyls and 6-aminouracils in the presence of FeCl3·6H2O as catalyst under microwave irradiation has been demonstrated. Three-component reaction of α,β-unsaturated aldehydes like cinnamaldehyde/crotonaldehyde, cyclic 1,3-diketones such as 2-hydroxy-1,4-naphthaquinone/dimedone and 6-aminouracils provides regioselective pyrimidine-fused tetrahydropyridines tethered with cyclic 1,3-diketones. On the other hand, replacing cyclic 1,3-diketones by 4-hydroxycoumarin and keeping all other conditions the same provided a two-component pyrimidine-fused pyridines. The salient features of this methodology are operational simplicity, short reaction time, good-to-moderate yields of the products, easy purification method and regioselective products having medicinally important heterocyclic rings such as pyrimidine, tetrahydropyridine or pyridine.

Ultrasonic Activated, Highly Efficient and Regioselective Synthesis of a Novel Pyrrole- Linked benzo[f]chromene Scaffold in a Green Media

Aim and Objective: Chromene scaffold is one of the most famous oxygen heterocycles that have widely found in plants playing pivotal roles in medicinal and synthetic chemistry. This study was undertaken to provide a green protocol for the synthesis of novel functionalized chromen-pyrrole hybrids by a regioselective three-component reaction via both conventional and sonochemical methods. Because of fascinating features of these individual cores, a hybride molecular structure comprising of pyrrole and chromene moieties could result in a novel single molecule with increased efficacy. Materials and Methods: The synthesis of novel functionalized chromen-pyrrole hybrids was accomplished by regioselective three-component reaction of β-naphthol, 3-(1-methyl-1H-pyrrol-2-yl)-3-oxopropanenitrile and diverse aromatic aldehydes catalyzed by triethylamine in H2O-EtOH via both conventional and sonochemical methods. The impact of some variants such as solvents, catalysts and temperature was also probed under both conventional heating and sonochemical methods to accomplish the optimized reaction condition. The synthesized products were screened for antibacterial activity against Gram positive (Ml, Bs, Sa) and Gram negative bacteria (Ps, Ec). Results: In initial attempt, the reaction of equimolar amounts of 2-fluorobenzaldehyde, 3-(1-methyl-1H-pyrrol- 2-yl)-3-oxopropanenitrile and β-naphthol was selected as a model reaction. The role of various solvents, temperature and different acidic and basic catalysts on the model reaction was examined. The optimized condition was the use of 20 mol% triethylamine in H2O-EtOH (1:1) under ultrasound irradiation at 65°C. The scope of this reaction was screened with respect to various substituted aromatic aldehydes. Considering the results, the electronic features of substituents affected the performance of this condensation. The reaction with aromatic aldehydes containing electron-withdrawing groups proceeded in lower reaction time, affording the productds in high to excellent yields while aldehydes with electron-donating groups reacted more slowly. This three-component reaction also provided a suitable procedure for the synthesis of bis-(chromen-pyrrole) in excellent yield. All of the synthesized products had significant antibacterial activity against the screened bacteria (Ml, Bs, Sa, Ps, Ec). Conclusion: A streamlined, regioselective and ecofriendly ultrasonic-promoted procedure for the synthesis of novel substituted benzo[f]chromenes from one-pot condensation of β-naphthol, 3-(1-methyl-1H-pyrrol-2-yl)-3- oxopropanenitrile and structurally diverse aldehydes catalyzed by triethylamine was developed. This green protocol furnishes all the products in reduced reaction times and high yields. In addition, the synthesized novel compounds showed narrow to wide spectral activity against the tested strains.

Regioselective Three-Component Reaction of Pyridine N-Oxides, Acyl Chlorides, and Cyclic Ethers.

A novel three-component reaction of pyridine N-oxides, acyl chlorides, and cyclic ethers is described. Treatment of an electron-deficient pyridine N-oxide with an acyl chloride in the presence of a cyclic ether at 25-50 °C leads to a substituted pyridine as a single regioisomer in up to 58% isolated yield. Isotopic-labeling experiments and substrate scope support the reaction proceeding through a carbene intermediate.

A regioselective three-component reaction for synthesis of novel 1′ H-spiro[isoindoline-1,2′-quinazoline]-3,4′(3′ H)-dione derivatives

A ring opening and regioselective three-component reaction of isatoic anhydride, isatins, and aromatic or aliphatic primary amines in the presence of catalytic amount of KAl(SO 4) 2·12H 2O (alum) to yield a novel series of 1′ H-spiro[isoindoline-1,2′-quinazoline]-3,4′(3′ H)-dione is described.