Research on transition metals for the multicomponent synthesis of benzo-fused γ-lactams

Benzo-fused γ-lactams are fundamental in medicinal chemistry, acting as essential elements for various therapeutic agents due to their structural adaptability and capability to enhance biological activity. In their synthesis, transition metals play a pivotal role as catalysts, offering more efficient alternatives to traditional methods by facilitating C-N bond formation through mechanisms like intramolecular coupling. Recent advances have especially spotlighted transition-metal-catalyzed C-H amination reactions for directly converting C(sp2)-H to C(sp2)-N bonds, streamlining the creation of these compounds. Furthermore, biocatalytic approaches have emerged, providing asymmetric synthesis of lactams with high yield and enantioselectivity. This review examined the transition metal-catalyzed synthesis techniques for producing benzo-fused γ-lactams, marking a significant leap in organic synthesis by proposing more effective, selective, and greener production methods. It serves as a valuable resource for researchers in the fields of transition metal catalysts and those engaged in synthesizing these lactams.

Isoindolinone Synthesis via One-Pot Type Transition Metal Catalyzed C-C Bond Forming Reactions

Isoindolinone structure is an important privileged scaffold found in a large variety of naturally occurring as well as synthetic, biologically and pharmaceutically active compounds. Owing to its crucial role in a number of applications, the synthetic methodologies for accessing this heterocyclic skeleton have received significant attention during the past decade. In general, the synthetic strategies can be divided into two categories: First, direct utilization of phthalimides or phthalimidines as starting materials for the synthesis of isoindolinones; and second, construction of the lactam and/or aromatic rings by different catalytic methods, including C-H activation, cross-coupling, carbonylation, condensation, addition and formal cycloaddition reactions. Especially in the last mentioned, utilization of transition metal catalysts provides access to a broad range of substituted isoindolinones. Herein, the recent advances (2010-2020) in transition metal catalyzed synthetic methodologies via formation of new C-C bonds for isoindolinones are reviewed.

Dihydroquinazolinones via A3 -Type Reactions of N-Carbamoyliminium Ions

A variant of the A³ coupling reaction was developed utilizing in situ generated N-carbamoyliminium ions. The tandem INCIC/A³ -coupling sequence provided a facile one-pot synthesis of dihydroquinazolinone derivatives. The scope of the reaction was demonstrated in solution as well as on solid support. The reaction was further combined with peptide synthesis, S_N Ar reactions, CuAAC triazole formation or bromination, providing additional opportunities for further diversification of the dihydroquinazolinone scaffolds.

Nanofibrils of a CuII-Thiophenyltriazine-Based Porous Polymer: A Diverse Heterogeneous Nanocatalyst

Herein, we report knitting of a thiophenyltriazine-based porous organic polymer (TTPOP) with high surface area and high abundance of nitrogen and sulfur sites, synthesized through a simple one-step Friedel-Crafts reaction of 2,4,6-tri(thiophen-2-yl)-1,3,5-triazine and formaldehyde dimethyl acetal in the presence of anhydrous FeCl₃, and thereafter grafting of Cu(OAc)₂·H₂O in the porous polymer framework to achieve the potential catalyst (Cu^II-TTPOP). TTPOP and Cu^II-TTPOP were characterized thoroughly utilizing solid-state ¹³C-CP MAS NMR, Fourier transform infrared, wide-angle powder X-ray diffraction, thermogravimetric analysis, and X-ray photoelectron spectroscopy and surface imaging by transmission electron microscopy and field emission scanning electron microscopy. The porosity of the nanomaterials was observed in the surface imaging and verified through conducting N₂ gas adsorption techniques. Keeping in mind the tremendous importance of C-C and C-N coupling and cyclization processes, the newly synthesized Cu^II-TTPOP was employed successfully for a wide range of organic catalytic transformations under mild conditions to afford directly valuable diindolylmethanes and spiro-analogues, phthalimidines, propargyl amines, and their sugar-based chiral compounds with high yields using readily available substrates. The highly stable new heterogeneous catalyst showed outstanding sustainability, robustness, simple separation, and recyclability.

Rapid and efficient synthesis of a novel cholinergic muscarinic M1 receptor positive allosteric modulator using flash chemistry

Continuous flow-flash synthesis of a 2-bromobenzaldehyde derivative 18 as a key intermediate of a novel cholinergic muscarinic M₁ positive allosteric modulator 1 bearing an isoindolin-1-one ring system as a pharmacophore has been achieved using flow microreactors through selective I/Li exchange of 1-bromo-2-iodobenzene derivative 17 with BuLi and subsequent formylation at -40 °C of the highly reactive 2-bromophenyllithium intermediate using DMF, which is difficult to achieve by a conventional batch process due to the conversion of the highly reactive 2-bromophenyllithium intermediate into benzyne even at -78 °C. Late-stage cyclization to give the isoindolin-1-one ring system, through reductive amination of 18 followed by palladium-catalyzed carbonylation with carbon monoxide and intramolecular cyclization, efficiently afforded 1 for its further research and development.

Multicomponent reactions (MCRs): a useful access to the synthesis of benzo-fused γ-lactams

Benzo-fused γ-lactam rings such as isoindolin-2-ones and 2-oxindoles are part of the structure of many pharmaceutically active molecules. They can be often synthesized by means of multicomponent approaches and recent contributions in this field are summarized in this review. Clear advantages of these methods include the efficiency in saving raw materials and working time. However, there is still a need of new catalytic systems to allow the enantioselective preparation of these heterocycles by multicomponent reactions.

5-Annulation of Ketoimines: TFA-Catalyzed Construction of Isoindolinone-3-carboxylates and Development of Photophysical Properties

Herein we have demonstrated the first report on 5-annulation of ketoimines to valuable isoindolinone-3-carboxylates. Instead of commonly used aldimine substrates, relatively less reactive ketoimines are employed for developing a TFA catalyzed organoreductive cyclization to furnish a variety of isoindolinones in excellent yield and reaction rate under mild reaction conditions. This is a metal-free event, which proceeds through a one pot ketoimine formation, hydride transfer from an organic reductant 2-(naphthalen-2-yl)-2,3-dihydrobenzo[ d]thiazole, and followed by five member cyclization sequences through TFA-activation of imine and ester groups. Studies on ESI-MS kinetics, leaving group aptitude, and control experiments led us to propose the mechanistic pathway of the new ketoimine-lactamization reaction. We have shown the synthetic utility of the emerging synthons through easy transformation of isoindolinones to different synthetic analogues. We investigated photophysical properties of the small molecules for their futuristic application as a pharmaceutical and materials, and the heterocycles displayed brilliant fluorescence activity.

Convenient access to 5-arylisoindolo[2,1- α]quinolin-11(6a H)-ones

Substituted isoindoloquinolinones were obtained from N-aryl-3-hydroxyisoindolinones and aryl alkynes under Lewis acid-catalyzed conditions in 30-99% yields.

An efficient approach to 3-oxoisoindoline-1-difluoroalkyl derivatives via a metal triflate-catalyzed Mannich/lactamization cascade reaction

An efficient approach for the synthesis of N-substituted 3-oxoisoindoline-1-difluoroalkyl derivatives via a one-pot cascade reaction has been developed.

Ni(II)-Catalyzed Highly Stereo- and Regioselective Syntheses of Isoindolinones and Isoquinolinones from in Situ Prepared Aldimines Triggered by Homoallylation/Lactamization Cascade

An efficient route to isoindolinones and isoquinolinones has been achieved via a domino Ni-catalyzed homoallylation/lactamization from in situ prepared imines, derived from o-formyl benzoates and o-formyl arylacetates, with conjugated dienes promoted by diethylzinc. The reaction proceeds smoothly at room temperature for a variety of aldehydes, amines, and dienes. The method involves one C-C and two C-N bond forming events under operationally simple conditions.

Concise synthesis of 12a-methyl-11-aryl-1,2-dihydrobenzo[f]pyrrolo[1,2-a]quinolin-3(12aH)-ones as racemic 14-azaestrogen analogs

A concise method for the synthesis of 14-azasteroid analogs with angular methyl group at C-13 of the steroidal nucleus has been reported in this paper. We have developed an interesting cascade reaction of arylacetylenes and N-(naphthalen-2-yl)pent-4-ynamides under gold (III)-catalysis to produce novel tetracyclic 12a-methyl-11-aryl-1,2-dihydrobenzo[f]pyrrolo[1,2-a]quinolin-3(12aH)-ones which may be viewed as 14-azaestrogen analogs.

One-pot synthesis of spiropyrroloquinoline-isoindolinone and their aza-analogs via the Ugi-4CR/metal-free intramolecular bis-annulation process

This presentation discloses a one-pot synthesis of a series of spiropyrroloquinoline isoindolinone and spiropyrroloquinoline aza-isoindolinone scaffolds.