Pd-Catalyzed Three-Component Domino Reaction of Vinyl Benzoxazinanones for Regioselective and Stereoselective Synthesis of Allylic Sulfone-Containing Amino Acid Derivatives

Iridium-Catalyzed Intramolecular Asymmetric Allylation of Vinyl Benzoxazinones for the Synthesis of Chiral 4H-3,1-Benzoxazines via Kinetic Resolution

Chiral benzoxazinones and 4H-3,1-benzoxazines as important motifs are widely found in abundant pharmaceuticals and biological molecules. We herein successfully developed the first kinetic resolution (KR) process of racemic benzoxazinones through Ir-catalyzed asymmetric intramolecular allylation, furnishing a wide range of chiral benzoxazinones and 4H-3,1-benzoxazines with excellent results via outstanding KR performances (with the s factor up to 170). This protocol exhibited broad substrate scope generality and good functional group tolerance, and the chiral 4H-3,1-benzoxazine products could be readily transformed to other useful optically active heterocycles.

Palladium-Catalyzed Asymmetric Cascade Intramolecular Cyclization/Intermolecular Michael Addition Reaction of Allenyl Benzoxazinones with 1-Azadienes

We herein designed and synthesized allenyl benzoxazinones of a novel type, which were then involved in a Pd-catalyzed asymmetric cascade intramolecular cyclization/intermolecular Michael addition reaction with 1-azadienes. A broad range of chiral C2-functionalized quinoline derivatives were afforded in moderate to good yields (up to 93%) with high enantioselectivities (up to 93% ee) in this reaction.

Blue Light-Promoted Cross-Coupling of α-Diazo Esters with Isocyanides: Synthesis of Ester-Functionalized Ketenimines

A metal-free scalable synthesis of functionalized ketenimines from alkyl α-(aryl/heteroaryl)-α-diazoacetates and alkyl isocyanides induced by blue light irradiation has been developed. The reaction proceeds at room temperature without any photocatalyst and provides ketenimines in moderate to good yields. Density functional theory (DFT) calculations and the experimental study showed that aryl(alkoxycarbonyl)carbenes in both singlet and triplet states can react with isocyanides but only the reaction of the former leads to the smooth formation of ketenimines. The obtained ketenimines were used for the synthesis of functionalized amidines under mild metal-free conditions.

Multicomponent Reactions Involving Diazo Reagents: A 5-Year Update

This review summarizes recent developments in multicomponent reactions of diazo compounds. The role of diazo reagent and the type of interaction between components was analyzed to structure the discussion. In contrast to previous reviews on related topics mostly focused on metal catalyzed transformations, a substantial amount of organocatalytic or catalyst-free methodologies is covered in this work.

Access to acridones by tandem copper(I)-catalyzed electrophilic amination/Ag(I)-mediated oxidative annulation of anthranils with arylboronic acids

An efficient and practical approach for the synthesis of medicinally important acridones was developed from anthranils and commercially available arylboronic acids by a tandem copper(I)-catalyzed electrophilic amination/Ag(I)-mediated oxidative annulation strategy. This new and straightforward protocol displayed a broad substrate scope (25 examples) and high functional group tolerance. What's more, a possible mechanistic proposal was also presented.

Access to 5,6-Spirocycles Bearing Three Contiguous Stereocenters via Pd-Catalyzed Stereoselective [4 + 2] Cycloaddition of Azadienes

We present herein a highly diastereo- and enantioselective Pd-catalyzed [4 + 2] cycloaddition of benzofuran-derived azadienes with vinyl benzoxazinanones, which represents a rare highly stereoselective cycloaddition of this class of fused azadienes as a two-atom synthon. The use of a phosphoramidite ligand bearing a chiral secondary amine with a simple biphenyl backbone proved to be the key to construct the novel spirocyclic tetrahydroquinoline scaffold containing three contiguous stereocenters as a single diastereomer in high enantioselectivity.

Catalytic Asymmetric Construction of a 1,2,4-Benzotriazepine Skeleton via Diastereo- and Enantioselective Decarboxylative [4 + 3] Cyclization

We have developed a protocol for palladium-catalyzed decarboxylative [4 + 3] cycloaddition reactions between 4-vinyl benzoxazinanones and azomethine imines to generate moderate to good yields of structurally diverse 1,2,4-benzotriazepines bearing two stereogenic centers with good to excellent stereoselectivities. This protocol not only addresses the challenge of asymmetrically constructing compounds with a 1,2,4-benzotriazepine skeleton but also demonstrates the utility of decarboxylative cycloadditions for the synthesis of enantioenriched polycyclic compounds.

Synthesis and applications of sodium sulfinates (RSO2Na): a powerful building block for the synthesis of organosulfur compounds

This review highlights the preparation of sodium sulfinates (RSO2Na) and their multifaceted synthetic applications. Substantial progress has been made over the last decade in the utilization of sodium sulfinates emerging as sulfonylating, sulfenylating or sulfinylating reagents, depending on reaction conditions. Sodium sulfinates act as versatile building blocks for preparing many valuable organosulfur compounds through S-S, N-S, and C-S bond-forming reactions. Remarkable advancement has been made in synthesizing thiosulfonates, sulfonamides, sulfides, and sulfones, including vinyl sulfones, allyl sulfones, and β-keto sulfones. The significant achievement of developing sulfonyl radical-triggered ring-closing sulfonylation and multicomponent reactions is also thoroughly discussed. Of note, the most promising site-selective C-H sulfonylation, photoredox catalytic transformations and electrochemical synthesis of sodium sulfinates are also demonstrated. Holistically, this review provides a unique and comprehensive overview of sodium sulfinates, which summarizes 355 core references up to March 2020. The chemistry of sodium sulfinate salts is divided into several sections based on the classes of sulfur-containing compounds with some critical mechanistic insights that are also disclosed.

Marine furanocembranoids-inspired macrocycles enabled by Pd-catalyzed unactivated C(sp3)-H olefination mediated by donor/donor carbenes

Biomimetic modularization and function-oriented synthesis of structurally diversified natural product-like macrocycles in a step-economical fashion is highly desirable. Inspired by marine furanocembranoids, herein, we synthesize diverse alkenes substituted furan-embedded macrolactams via a modular biomimetic assembly strategy. The success of this assembly is the development of crucial Pd-catalyzed carbene coupling between ene-yne-ketones as donor/donor carbene precursors and unactivated Csp³‒H bonds which represents a great challenge in organic synthesis. Notably, this method not only obviates the use of unstable, explosive, and toxic diazo compounds, but also can be amenable to allenyl ketones carbene precursors. DFT calculations demonstrate that a formal 1,4-Pd shift could be involved in the mechanism. Moreover, the collected furanocembranoids-like macrolactams show significant anti-inflammatory activities against TNF-α, IL-6, and IL-1β and the cytotoxicity is comparable to Dexamethasone.

Furanocembranoid-like natural products with the alkene-substituted furan scaffold display a range of biological activities, but are difficult to access. Here, the authors report a modular biomimetic strategy to synthesise diverse alkene-substituted furan-containing macrolactams via palladium-catalysed unactivated Csp³-H olefination.

Rh-Catalyzed C-H alkylation enabling modular synthesis of CF3-substituted benzannulated macrocyclic inhibitors of B cell responses

Inspired by aspirin and chalcone, herein, we describe a modular biomimetic strategy to achieve a new class of CF3-bearing benzannulated macrolactams. The key to the success of macrolactams was the utilization of a highly chemoselective Rh(iii)-catalyzed native carboxylic acid-directed C-H alkylation. Moreover, the unique CF3-containing benzannulated macrocycles showed decent immunosuppressive effects on B cells in vitro, including proliferation, activation, and antibody production upon specific stimulation implicating TLR and BCR signaling.

Pd/LA-catalyzed decarboxylation enabled exclusive [5 + 2] annulation toward N-aryl azepanes and DFT insights

A practical approach towards the synthesis of non-fused N-aryl azepane derivatives with diversity is described. DFT calculations revealed the origins of this unusual exclusive [5 + 2] rather than empirical [3 + 2] annulation process.

Recent advances in annulation reactions based on zwitterionic π-allyl palladium and propargyl palladium complexes

Carbocyclic and heterocyclic compounds could be constructed through the palladium-catalyzed annulation reactions of zwitterionic π-allyl palladium or propargyl palladium complexes with unsaturated electrophiles.

A modular biomimetic strategy for the synthesis of macrolide P-glycoprotein inhibitors via Rh-catalyzed C-H activation

One of the key challenges to overcome multidrug resistance (MDR) in cancer is the development of more effective and general strategies to discover bioactive scaffolds. Inspired by natural products, we describe a strategy to achieve this goal by modular biomimetic synthesis of scaffolds of (Z)-allylic-supported macrolides. Herein, an Rh(III)-catalyzed native carboxylic acid-directed and solvent-free C−H activation allylation with high stereoselectivity and chemoselectivity is achieved. The generated poly-substituted allylic alcohol as a multifunctional and biomimetic building block is crucial for the synthesis of (Z)-allylic-supported macrolides. Moreover, the unique allylic-supported macrolides significantly potentiate the sensitivity of tumor cells to cytotoxic agents such as vinorelbine and doxetaxel by reversing p170-glycoprotein-mediated MDR. Our findings will inspire the evolution of synthetic chemistry and open avenues for expedient and diversified synthesis of bioactive macrocyclic molecules.

One strategy to address multidrug resistance in cancer is the development of modular methods to access bioactive scaffolds. Here, the authors report a Rh(III)-catalyzed carboxylic acid-directed C(sp²)−H allylation and apply it to the modular synthesis of (Z)-allylic macrolides which enhance antitumoral drug activity.

Arylation and alkenylation of activated alkyl halides using sulfonamides

A variety of quaternary aryl amino acid derivatives can be synthesised using tandem S_N2/Smiles rearrangement chemistry involving aryl sulfonamides and α-chloro carbonyl compounds.

An Update of Transition Metal-Catalyzed Decarboxylative Transformations of Cyclic Carbonates and Carbamates

Functionalized cyclic organic carbonates and carbamates are frequently used in a number of transition metal-catalyzed decarboxylative reactions for the construction of interesting molecules. These decarboxylative transformations have attracted more and more research attention in recent years mainly due to their advantages of less waste generation and versatile reactivities. On the basis of previous reviews on this hot topic, the present review will focus on the development of transition metal-catalyzed decarboxylative transformations of functionalized cyclic carbonates and carbamates in the last two years.

A concise construction of 4-alkynylquinazolines via [4 + 2] annulation of 4-alkynylbenzoxazinanones with acylhydroxamates under transition-metal-free conditions

A concise and highly efficient method for the construction of valuable 4-alkynylquinazolines under transition-metal-free conditions was developed via [4 + 2] annulation of 4-alkynylbenzoxazinanones with acylhydroxamates in good to excellent yields.