New Reactivity of Oxaziridine: Pd(II)-Catalyzed Aromatic C–H Ethoxycarbonylation via C–C Bond Cleavage

Rhodium-catalysed additive-free alkoxycarbonylation of indoles: 2,4,6-trimethylbenzoic acid-based carbonate anhydrides as a versatile alkoxycarboxyl source

We report a CO-free approach to indole-2-carboxylic esters: rhodium-catalysed C(2)-alkoxycarbonylation of indoles with 2,4,6-trimethylbenzoic acid-based carbonate anhydrides. Selective C-O bond cleavage of the anhydrides facilitates the introduction of various alkoxycarbonyl groups. Control experiments suggest that merging a rhodium catalyst and KI promotes the in situ formation of the RhI species.

Palladium-Catalyzed ortho-C-H Alkoxycarbonylation of Aromatic Aldehydes via a Transient Directing Group Strategy

Transient directing groups (TDGs) can be a powerful strategy for directly functionalizing C-H bonds of aldehydes. We report a palladium-catalyzed o-C-H alkoxycarbonylation of benzaldehydes using a catalytic amount of aromatic amine to form a transient imine that plays the role of a monodentate TDG. The reaction conditions were applied to a broad range of aldehydes, and the corresponding 2-formyl benzoates were used as direct precursors for the synthesis of phthalides and 1-isoindolinones.

Open clamshell dinuclear palladium(ii) complexes possessing out-of-plane anisotropy

Double cyclometalation of planar, oligomeric phenylpyridines yielded dinuclear palladium(ii) complexes with novel out-of-plane anisotropy. An X-ray crystal structure analysis revealed that the complexes exhibit concave-convex geometry, and 1H NMR measurement evidenced the occurrence of stable out-of-plane anisotropy. The dipole moment and Pd-Pd interaction were investigated by theoretical calculations.

Palladium-Catalyzed Carboxylate-Assisted Ethoxycarboxylation of Aromatic Acids To Synthesize Monoethyl Phthalate Derivatives with Ethyl Bromodifluoroacetate

A novel and efficient approach for direct carbonation of aromatic acids with ethyl bromodifluoroacetate as the carbonyl source is reported. A broad range of substrates bearing various functional groups were tolerated, leading to monoalkyl phthalate derivatives in moderate to good yields.

Direct synthesis of 8-acylated quinoline N-oxidesviapalladium-catalyzed selective C–H activation and C(sp2)–C(sp2) cleavage

An efficient method for the synthesis of 8-acylated quinoline N-oxides from the reaction of quinoline N-oxides with α-diketonesviaC–C bond cleavage was developed. A variety of quinoline N-oxides and α-diketones with different groups was well tolerated in this system.

Recent Advances in the Catalytic Asymmetric Reactions of Oxaziridines

Oxaziridines have emerged as powerful and elegant oxygen- and nitrogen-transfer agents for a broad array of nucleophiles, due to the remarkably high and tunable reactivities. However, the asymmetric catalysis involving oxaziridines is still in its infancy. Herein, this review aims to examine recent advances in the catalytic asymmetric transformations of oxaziridines, including oxidation, amination, cycloaddition and deracemization.

Synthesis of phthalic acid derivatives via Pd-catalyzed alkoxycarbonylation of aromatic C-H bonds with alkyl chloroformates

A Pd(ii)-catalyzed alkoxycarbonylation of aromatic C-H bonds with alkyl chloroformates has been developed. A broad range of benzamides and alkyl chloroformates are compatible with this protocol. The reaction is operationally simple and scalable. The direct group could be readily removed to access substituted phthalic acid esters (PAEs), 1,2-dibenzyl alcohols and phthalamides. Besides alkoxycarbonylation of benzamide β-C-H bonds, γ-alkoxycarbonylation of 2-phenylacetamide is also feasible.

Palladium-catalyzed direct C–H ethoxycarbonylation of 2-aryl-1,2,3-triazoles and efficient synthesis of suvorexant

Palladium-catalyzed direct ethoxycarbonylation with diethyl azodicarboxylate was developed and its reaction mechanism was explored by using DFT calculations.

Practical Singly and Doubly Electrophilic Aminating Agents: A New, More Sustainable Platform for Carbon-Nitrogen Bond Formation

Given the importance of amines in a large number of biologically active natural products, active pharmaceutical ingredients, agrochemicals, and functional materials, the development of efficient C-N bond-forming methods with wide substrate scope continues to be at the frontier of research in synthetic organic chemistry. Here, we present a general and fundamentally new synthetic approach for the direct, transition-metal-free preparation of symmetrical and unsymmetrical diaryl-, arylalkyl-, and dialkylamines that relies on the facile single or double addition of readily available C-nucleophiles to the nitrogen atom of bench-stable electrophilic aminating agents. Practical single and double polarity reversal (i.e., umpolung) of the nitrogen atom is achieved using sterically and electronically tunable ketomalonate-derived imines and oximes. Overall, this novel approach represents an operationally simple, scalable, and environmentally friendly alternative to transition-metal-catalyzed C-N cross-coupling methods that are currently used to access structurally diverse secondary amines.

Oxaziridine cleavage with a low-valent nickel complex: competing C–O and C–N fragmentation from oxazanickela(ii)cyclobutanes

Nickel(0) was found to oxidatively add to oxaziridines to form oxazanickelacyclobutanes which cleave to yield complicated mixtures, including nickel imido and aldehyde complexes.

Merging allylic C-H bond activation and C-C bond cleavage en route to the formation of a quaternary carbon stereocenter in acyclic systems

This protocol describes a diastereoselective approach for the synthesis of complex molecular architectures containing two stereogenic centers in a 1,4 relationship, one of which being an all-carbon quaternary stereogenic center. Such molecules could be intermediates in the synthesis of steroids, for example. Conceived as a single-flask synthetic sequence from ω-ene cyclopropanes, the protocol involves a concerted allylic C-H and C-C bond activation promoted by the Negishi reagent (Cp₂Zr(η²-butene)). This zirconium-promenade-based procedure affords bifunctionalized products in high diastereomeric ratios after reaction of ω-ene cyclopropanes with the Negishi complex, followed by a thermal treatment and sequential addition of two different electrophiles. The method proves to be particularly efficient when carbonyl compounds are used as first electrophiles and hydrogen or elemental halides are used as second electrophiles. In addition, it offers the opportunity to create new C-C bonds via remote functionalization of a (sp³)-C-H bond, a result of a copper or copper/palladium transmetalation step that extends the scope of the process to alkyl, acyl and aromatic halide compounds as second electrophiles. The typical described protocol allows the synthesis of the highly diastereo-enriched 2-((1R*,2S*)-2-butyl-2 propylcyclopropyl)ethanol and may provide a new entry to access complex molecular segments of natural products such as steroids or C30 botryococcene. It requires a simple reaction setup and takes ∼18.5 h to run the reaction and 2 h for isolation and purification.

Stereoselective alkoxycarbonylation of unactivated C(sp3)-H bonds with alkyl chloroformates via Pd(II)/Pd(IV) catalysis

Several examples on Pd-catalysed carbonylation of methyl C(sp³)-H bonds with gaseous CO via Pd(II)/Pd(0) catalysis have been reported. However, methylene C(sp³)-H carbonylation remains a great challenge, largely due to the lack of reactivity of C-H bonds and the difficulty in CO migratory insertion. Herein, we report the stereoselective alkoxycarbonylation of both methyl and methylene C(sp³)-H bonds with alkyl chloroformates through a Pd(II)/Pd(IV) catalytic cycle. A broad range of aliphatic carboxamides and alkyl chloroformates are compatible with this protocol. In addition, this process is scalable and the directing group could be easily removed under mild conditions with complete retention of configuration.

Palladium-catalyzed C–H bond carboxylation of acetanilides: an efficient usage of N,N-dimethyloxamic acid as the carboxylate source

A palladium-catalyzed carboxylation of acetanilide and N,N-dimethyloxamic acid for the synthesis of N-acyl-anthranilic acids is described. N,N-Dimethyloxamic acid can act as an effective carboxylation precursor with K₂S₂O₈ as the oxidant and Pd(OAc)₂ as the catalyst.

Transition metal-catalysed couplings between arenes and strained or reactive rings: combination of C–H activation and ring scission

Transition metal-catalysed systems of C–H activation of arenes in combination with opening of strained or reactive three, four, and five membered rings are summarized in this review.

Recent advances in the transition metal catalyzed carbonylation of alkynes, arenes and aryl halides using CO surrogates

Transition metal catalyzed carbonylation reactions using carbon monoxide as the C-1 source have occupied an all important position in catalysis which is subsequently related to organic synthesis and industrial synthesis of molecules.

Palladium-catalyzed direct ortho-ethoxycarbonylation of azobenzenes and azoxybenzenes with diethyl azodicarboxylate

A palladium-catalyzed direct ortho-ethoxycarbonylation of azobenzenes and azoxybenzenes with diethyl azodicarboxylate (DEAD) was developed under mild reaction conditions.

Transition metal-catalyzed C–H bond functionalizations by the use of diverse directing groups

In this review, a summary of transition metal-catalyzed C–H activation by utilizing the functionalities as directing groups is presented.

Ruthenium-catalyzed double-fold C–H tertiary alkoxycarbonylation of arenes using di-tert-butyl dicarbonate

An efficient ruthenium-catalyzed double-fold C–H bond alkoxycarbonylation of arenes was developed using commercially available Boc₂O as the tertiary esterification reagent.

Rhodium(iii)-catalyzed coupling of N-sulfonyl 2-aminobenzaldehydes with oxygenated allylic olefins through C–H activation

N-Sulfonyl-2-aminobenzaldehyde undergoes C–H activation and coupling with oxygenated allylic olefins under redox-neutral conditions with high efficiency.