Access to 2′,3′-dihydro-1′H-spiro[indoline-3,4′-pyridin]-2-ones via amino acid derived phosphine-catalyzed asymmetric [4+2] annulation with easily available oxindole-derived α,β-unsaturated imines

Contemporary progress in the green synthesis of spiro-thiazolidines and their medicinal significance: a review

The development of new strategies for the production of nitrogen and sulfur-containing heterocycles remains an extremely alluring but challenging proposition. Among these heterocyclic compounds, spiro-thiazolidines are a distinct class of heterocyclic motifs with an all-encompassing range of pharmaceutical activities such as anti-histaminic, anti-proliferative, anesthetic, hypnotic, anti-fungal, anti-inflammatory, anti-HIV, anthelmintic, CNS stimulant, and anti-viral potentials. Consequently, investigators have produced these heterocycles through diversified intricate pathways as object structures for medicinal studies. Notwithstanding their innumerable manmade solicitations, there is yet no special periodical on MCRs concerning spiro-thiazolidine via green synthesis. Thus, this in-depth review encompasses the excursion of MCRs to spiro-thiazolidines, including the environment-friendly synthetic approaches, reaction situations, rationale behind the optimal selection of catalyst, scope, anticipated mechanism, and biological activities. In this review, we have focussed on the furthermost current developments in spiro-thiazolidine creation under different conditions, such as ionic liquid-assisted, microwave-assisted, on-water, solid-supported acid-catalyzed, asymmetric, and nanocatalyst-assisted syntheses, developed over the last 8 years. This study details works regarding the total amalgamation of spiro-thiazolidines under N- and S-containing heterocycles. Furthermore, this article summarizes the developments of artificially and pharmaceutically important spiro-thiazolidine candidates.

The catalytic influence of phosphotungstic acid-functionalized Fe3O4 MNPs blended with TiO2 on the synthesis of novel spiro-acridines and the evaluation of their medicinal potential through molecular docking studies

This manuscript describes an effective and rapid three-component synthesis of a novel series of spiro-acridine derivatives by integrating the pharmacologically dynamic hydantoin–phenytoin as the prime synthetic equivalent. The process was accelerated by Fe₃O₄@TiO₂-PTA magnetic nanoparticles (MNPs), which acted as the heterogeneous catalytic system, under ultrasonic conditions. The reaction was performed in the green PEG-200 solvent under aerophilic conditions to obtain products with excellent yields. The characteristics of the synthesized magnetic nano-catalysts were corroborated through powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDAX), FT-IR, and VSM techniques. In addition, the structures of the synthesized compounds were ascertained on the basis of elemental analyses and spectro-analytical data (¹H NMR, ¹³C NMR, and mass spectrometry). High yields, smaller E-factor, considerable atom economy, easy recovery, and recyclability of the catalyst and solvent are the captivating features of the developed protocol. Moreover, in view of the ongoing global research on COVID-19, herein, we tried to identify the potential sites of the synthesized moiety that can suitably fit the receptor sites of the main protease of SARS-CoV-2 (SARS-CoV-2 M^pro).

This manuscript describes an effective and rapid three-component synthesis of a novel series of spiro-acridine derivatives by integrating the pharmacologically dynamic hydantoin–phenytoin as the prime synthetic equivalent.

Synthesis of heterocyclic compounds through nucleophilic phosphine catalysis

Nucleophilic phosphine catalysis is a practical and powerful tool for the synthesis of various heterocyclic compounds with the advantages of environmentally friendly, metal-free, and mild reaction conditions. The present report summarizes the construction of four to eight-membered heterocyclic compounds containing nitrogen, oxygen and sulphur atoms through phosphine-catalyzed intramolecular annulations and intermolecular [2+2], [3+2], [4+1], [3+1+1], [5+1], [4+2], [2+2+2], [3+3], [4+3] and [3+2+3] annulations of electron-deficient alkenes, allenes, alkynes and Morita-Baylis-Hillman carbonates.

Asymmetric Synthesis of Spirocyclic Oxindole δ-Lactams via NHC-Catalyzed Formal [2+4] Annulation of Aliphatic Aldehydes with Oxindole-Derived α,β-Unsaturated Ketimines

An N-heterocyclic carbene (NHC)-catalyzed formal [2+4] annulation reaction of aliphatic aldehydes with oxindole-derived α,β-unsaturated ketimines under oxidative conditions is reported, affording spirocyclic oxindole δ-lactams with good yields, moderate diastereoselectivies, and good to excellent enantioselectivies. This reaction can be readily carried out on a gram scale, and the products could be further transformed to other synthetically useful compounds.

Phosphine Organocatalysis

The hallmark of nucleophilic phosphine catalysis is the initial nucleophilic addition of a phosphine to an electrophilic starting material, producing a reactive zwitterionic intermediate, generally under mild conditions. In this Review, we classify nucleophilic phosphine catalysis reactions in terms of their electrophilic components. In the majority of cases, these electrophiles possess carbon-carbon multiple bonds: alkenes (section 2), allenes (section 3), alkynes (section 4), and Morita-Baylis-Hillman (MBH) alcohol derivatives (MBHADs; section 5). Within each of these sections, the reactions are compiled based on the nature of the second starting material-nucleophiles, dinucleophiles, electrophiles, and electrophile-nucleophiles. Nucleophilic phosphine catalysis reactions that occur via the initial addition to starting materials that do not possess carbon-carbon multiple bonds are collated in section 6. Although not catalytic in the phosphine, the formation of ylides through the nucleophilic addition of phosphines to carbon-carbon multiple bond-containing compounds is intimately related to the catalysis and is discussed in section 7. Finally, section 8 compiles miscellaneous topics, including annulations of the Hüisgen zwitterion, phosphine-mediated reductions, iminophosphorane organocatalysis, and catalytic variants of classical phosphine oxide-generating reactions.

Reactivity of Steroidal 1-Azadienes toward Carbonyl Compounds under Enamine Catalysis: Chiral Penta- and Hexacyclic Steroids

The synthesis and reactivity of a steroidal N-sulfonyl-1-azadiene, derived from 16-dehydropregnenolone acetate, toward carbonyl compounds under enamine catalysis is disclosed. An unexpected annulation reaction was observed involving an initial stereoselective conjugate addition of the in situ generated enamine to the steroidal 1-azadiene. The developed diastereoselective synthetic methodology is a novel approach to a new class of chiral pentacyclic and hexacyclic steroids.

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

Organocatalysis, now running its second decade of life, is being considered one of the main tools a synthetic chemist has to perform asymmetric catalysis. In this review the synthesis of six-membered rings, that contain multiple chiral centers, either by a ring closing process or by a functionalization reaction on an already existing six-membered ring, utilizing bifunctional (thio)ureas will be summarized. Initially, the use of primary amine-thioureas as organocatalysts for the above transformation is being discussed, followed by the examples employing secondary amine-thioureas. Finally, the use of tertiary amine-thioureas and miscellaneous examples are presented.

Recent developments in the synthesis and utilization of chiral β-aminophosphine derivatives as catalysts or ligands

In the last few years, the research area of chiral β-aminophosphines capable of promoting a wide range of diverse organic transformations has attracted more attention.

A catalyst-free, one-pot multicomponent synthesis of spiro-benzimidazoquinazolinones via a Knoevenagel–Michael-imine pathway: a microwave assisted approach

A multi-component route for the synthesis of spiro-benzimidazoquinazolinones was developed and its mechanism was studied.

Highly stereoselective [4+2] and [3+2] spiroannulations of 2-(2-oxoindolin-3-ylidene)acetic esters catalyzed by bifunctional thioureas

A new Michael-Michael cascade reaction between 2-(2-oxoindolin-3-ylidene)acetic esters 1 and nitroenoates 2, catalyzed by bifunctional thioureas, is investigated. The combination of the two Michael reactions results in a novel and facile [4+2] or [3+2] spiroannulation process, which is characterized by the following features: 1) two carbon-carbon bonds and four stereocenters, including a quaternary spiro carbon, are formed under mild conditions; 2) an unprecedented and stereochemically defined substitution pattern on the spirocarbocyclic unit is obtained; 3) the double-bond configuration of the donor-acceptor nitroenoate 2 determines the absolute configuration of the spiro center, whereas the remaining stereocenters are formed under control of the catalyst. The effect on the final stereochemical outcome of structural variations of each starting material, catalyst, and experimental conditions is analyzed in detail. In particular, the use of specifically designed chiral nitroenoates enables diverse polyfunctional spirocyclohexane derivatives containing six consecutive stereogenic centers to be constructed. To our knowledge, this is the first asymmetric organocatalytic strategy enabling both five- and six-membered β-nitro spirocarbocyclic oxindoles.