Catalytic asymmetric construction of 3,3'-spirooxindoles fused with seven-membered rings by enantioselective tandem reactions

Heteroatom-Controlled Three-Component [4 + 3] or [3 + 2] Annulation of Isatin-Derived Azomethine Ylide with Azadiene: Selective Synthesis of Spirooxindole-diazepines and Density Functional Theory Studies

A novel three-component [4 + 3] annulation reaction of isatin-derived azomethine ylides with azadienes was developed for the first time to efficiently synthesize spirooxindole-diazepines incorporating a benzothiophene moiety under catalyst-free conditions. Effects of the heteroatom of azadiene on the chemoselectivity was investigated. With the use of the azadiene bearing a benzofuran moiety as a substrate, the dominant reaction pathway was changed to an α-[3 + 2] annulation. When azadiene bearing an indenone moiety was used, a distinct γ-[3 + 2] annulation was observed. Density functional theory calculations revealed that a delicate balance between kinetic accessibility and the thermodynamic driving force controlled the competition of different annulation reactions.

Synthesis of benzimidazole-fused 1,4-benzoxazepines and benzosultams spiro-connected to a 2-oxindole core via a tandem epoxide-opening/SNAr approach

While hundreds of literature reports describe the preparation of spirooxindole-based five- and six-membered heterocycles, the construction of seven-membered heterocyclic rings spiro-connected to a 2-oxindole core has so far been less developed. Herein, we disclose a base-mediated (4 + 3) annulation of spiro-epoxyoxindoles and 2-(2-fluoroaryl)-1H-benzoimidazoles or 2-fluoro-N-arylbenzenesulfonamides toward the synthesis of two new classes of spirooxindole-based polycyclic systems. Mechanistically, this conceptually simple and high atom-economical reaction proceeds via an SN2-like intermolecular epoxide ring-opening, accompanied by a concomitant intramolecular SNAr reaction. From a synthetic aspect, the notable features of the process are its full regioselectivity, operational simplicity using readily available substrates under transition-metal-free conditions, high yields, and broad substrate scope.

Advances in chromone-based reactants in the ring opening and skeletal reconstruction reaction: access to skeletally diverse salicyloylbenzene/heterocycle derivatives

Salicyloylbenzene/heterocycles are privileged scaffolds found in many natural products and bioactive molecules. Numerous useful approaches for the preparation of these privileged scaffolds have been developed in recent years. Among these approaches, chromone-based reactants have demonstrated their importance in the synthesis of these salicyloylbenzene/heterocycle scaffolds with structural complexity and potential biological appeal. In this review, the recent advances in the synthesis of salicyloylbenzene/heterocycles are summarized and discussed according to the chromone-based reactants which could be achieved in one step via ring-opening and skeletal reconstruction reactions. Both the mechanisms and the applications of the corresponding products in organic and medicinal chemistry are also described.

Highly Selective Synthesis of Seven-Membered Azaspiro Compounds by a Rh(I)-Catalyzed Cycloisomerization/Diels-Alder Cascade of 1,5-Bisallenes

The synthesis of spiro compounds featuring seven- and six-membered rings in the spirobicyclic motif is successfully achieved through a cascade process encompassing a rhodium(I)-catalyzed cycloisomerization followed by a highly selective Diels–Alder homodimerization. The scope of the reaction is analyzed based on a series of synthetic substrates, and control experiments and DFT calculations led us to justify the exquisite degree of selectivity observed.

An overview of the applications of chiral phosphoric acid organocatalysts in enantioselective additions to CO and CN bonds

Since 2004, chiral phosphoric acids (CPAs) have emerged as highyl efficient organocatalysts, providing excellent results in a wide reaction scope. In this review, the applications of CPA for enantioselective additions to CO and CN bonds are covered.

An Efficient Approach for 3,3-Disubstituted Oxindoles Synthesis: Aryl Iodine Catalyzed Intramolecular C-N Bond Oxidative Cross-Coupling

Herein, we report the first intramolecular C-N bond formation of phenylpropanamide derivatives via organocatalytic oxidative reactions, affording 3,3-disubstituted oxindole derivatives with up to 99% yield. The high efficiency of this reaction is exemplified by the transition metal-free mild conditions and the ability to perform the reaction on a gram scale. Meanwhile, the DFT calculation of the catalytic oxidative transformation pathway has also been studied.

Synthesis of tetracyclic pyrido-fused dibenzodiazepines via a catalyst-free cascade reaction

An efficient, eco-friendly protocol has been described for the chemoselective synthesis of tetracyclic pyrido-fused dibenzodiazepines derivatives via catalyst-free, three-component reaction of dimedone, 1,2-diamines, 3-formylchromones, and malononitrile. The significant advantages of this cascade approach are to create two new rings and four new σ bonds containing three C-N and one C-C bond, as well as the breakdown of a C-O bond.

Multicomponent reactions as a potent tool for the synthesis of benzodiazepines

Benzodiazepines (BZDs), a diverse class of benzofused seven-membered N-heterocycles, display essential pharmacological properties and play vital roles in some biochemical processes. They have mainly been prescribed as potential therapeutic agents, which interestingly represent various biological activities such as anticancer, anxiolytic, antipsychotic, anticonvulsant, antituberculosis, muscle relaxant, and antimicrobial activities. The extensive biological activities of BZDs in various fields have encouraged medicinal chemists to discover and design novel BZD-based scaffolds as potential therapeutic candidates with the favorite biological activity through an efficient protocol. Although certainly valuable and important, conventional synthetic routes to these bicyclic benzene compounds contain methodologies often requiring multistep procedures, which suffer from waste materials generation and lack of sustainability. By contrast, multicomponent reactions (MCRs) have recently advanced as a green synthetic strategy for synthesizing BZDs with the desired scope. In this regard, MCRs, especially Ugi and Ugi-type reactions, efficiently and conveniently supply various complex synthons, which can easily be converted to the BZDs via suitable post-transformations. Also, MCRs, especially Mannich-type reactions, provide speedy and economic approaches for the one-pot and one-step synthesis of BZDs. As a result, various functionalized-BZDs have been achieved by developing mild, efficient, and high-yielding MCR protocols. This review covers all aspects of the synthesis of BZDs with a particular focus on the MCRs as well as the mechanism chemistry of synthetic protocols. The present manuscript opens a new avenue for organic, medicinal, and industrial chemists to design safe, environmentally benign, and economical methods for the synthesis of new and known BZDs.

Recent advances in organocatalytic asymmetric multicomponent cascade reactions for enantioselective synthesis of spirooxindoles

Catalytic asymmetric MCCRs for enantioselective synthesis of spirooxindoles by using chiral phosphoric acids, amines, bifunctional thiourea/squaramides and metal-based reagents as catalysts.

Asymmetric β,γ′-regioselective [4 + 3] and [4 + 2] annulations of α-vinylenals via cascade iminium ion-dienamine catalysis

α-Vinylenal substrates have been designed and applied in β,γ′-regioselective asymmetric [4 + 3] and [4 + 2] annulation reactions via cascade aminocatalysis.

A facile and efficient multicomponent ultrasound-assisted "on water" synthesis of benzodiazepine ring

A facile and efficient multicomponent synthesis of benzodiazepine ring in water under ultrasound irradiation is reported first time. The current procedure escapes traditional chromatography and purification process and provided the product in excellent yields of 95% as compared to conventional methods. The approach was also validated on gram-scale synthesis.

New development in the enantioselective synthesis of spiro compounds

In this review we summarize the latest developments in the enantioselective synthesis of spirocompounds. The most important organometallic and organocatalytic methodologies are highlighted.

Catalytic asymmetric synthesis of spirooxindoles: recent developments

The past four years have witnessed significant developments in the field of the catalytic asymmetric synthesis of spirooxindoles, and this feature article outlines the recent progress in this area, including the contributions of our group. This article is divided into sections according to the size and type of the generated spiro-ring fused at the C3-position of the oxindole core.

Facile, eco-friendly, catalyst-free synthesis of polyfunctionalized quinoxalines

A novel, facile and eco-friendly synthesis of quinoxalines from [Formula: see text] and 1,2-diamines was developed. An attractive feature of this protocol is that the desired products could be generated efficiently in water and without any catalyst, which is in accordance with the aim of green chemistry. A plausible mechanism has been proposed.

O, Divakar K, Paplal B, Kashinath D. “On water” synthesis of dibenzo-[1,4]-diazepin-1-ones using l-proline as an organocatalyst and under catalyst-free conditions, and their evaluation as α-glucosidase inhibitors

Functionalized dibenzo-[1,4]-diazepin-1-ones are synthesized using the “on-water” concept in the presence of l-proline (organocatalyst; 20 mol%) and under catalyst free conditions (sealed tube) in an aqueous medium.

Asymmetric Mannich reaction: highly enantioselective synthesis of 3-amino-oxindoles via chiral squaramide based H-bond donor catalysis

A facile formation of 3-aminooxindole derivatives from the reaction of 1,3-diketones with isatin (N-Boc) via an asymmetric Mannich reaction catalyzed by chiral cinchona alkaloid based squaramide containing H-bond donor catalysts.

Organocatalytic construction of spirooxindole naphthoquinones through Michael/hemiketalization usingl-proline derived bifunctional thiourea

Michael/hemiketalization of 2-hydroxy-1,4-naphthoquinone to oxindole ketoester was studied using a series of chiral bifunctional organocatalysts.

Construction of highly enantioselective spiro-oxindole derivatives with fused chromene via organocascade catalysis

A first highly enantioselective addition of naphthols and sesamol to indolylidene cyanoacetate derived from isatins was carried out in the presence of bi-functional quinine thiourea as organocatalyst.

Construction of Vicinal Tetrasubstituted Stereocenters with a C-F Bond through a Catalytic Enantioselective Detrifluoroacetylative Mannich Reaction

An efficient asymmetric detrifluoroacetylative Mannich reaction of 2-fluoro-1,3-diketones/hydrates with isatin-derived ketimines catalyzed by a chiral copper(II)-diamine complex has been realized. The reaction afforded a series of 3-substituted 3-amino-2-oxindoles bearing fluorine-containing vicinal tetrasubstituted stereocenters in high yields (up to 99%) with excellent diastereoselectivities (up to >20:1 dr) and enantioselectivities (up to 94% ee).

Stereoselective synthesis of 3-amino-2-oxindoles from isatin imines: new scaffolds for bioactivity evaluation

3-Substituted-3-aminooxindole motifs constitute the core structure of a number of natural products and drug candidates.

Enantioselective Construction of Spiro[indoline-3,2'-pyrrole] Framework via Catalytic Asymmetric 1,3-Dipolar Cycloadditions Using Allenes as Equivalents of Alkynes

The first catalytic asymmetric 1,3-dipolar cycloadditions (1,3-DCs) of isatin-derived azomethine ylide with allenes have been established, which efficiently assembly isatins, amino-esters and 2,3-allenoate into enantioenriched spiro[indoline-3,2'-pyrrole] derivatives with a quaternary stereogenic center in generally high enantioselectivities (80-98% ee). In this allene-involved 1,3-DC, an unexpected spirooxindole framework bearing an intra-annular C═C double bond was generated, which is quite different from previously reported 1,3-DCs of allenes. This approach not only confronted the great challenge in using allenes as dipolarophiles of 1,3-DCs, but also provided a unique strategy of using allenes as equivalents of alkynes to construct spiro[indoline-3,2'-pyrrole] structure. Besides, this reaction also represents the first catalytic asymmetric ketone-involved 1,3-DCs of allenes, which will also greatly enrich the research contents of 1,3-DCs, the chemistry of allenes as well as the synthetic methods of spirooxindoles.