Palladium-Catalyzed Decarboxylative Acylation ofO-Phenyl Carbamates with α-Oxocarboxylic Acids at Room Temperature

The Versatile and Strategic O-Carbamate Directed Metalation Group in the Synthesis of Aromatic Molecules: An Update

The aryl O-carbamate (ArOAm) group is among the strongest of the directed metalation groups (DMGs) in directed ortho metalation (DoM) chemistry, especially in the form Ar-OCONEt2. Since the last comprehensive review of metalation chemistry involving ArOAms (published more than 30 years ago), the field has expanded significantly. For example, it now encompasses new substrates, solvent systems, and metalating agents, while conditions have been developed enabling metalation of ArOAm to be conducted in a green and sustainable manner. The ArOAm group has also proven to be effective in the anionic ortho-Fries (AoF) rearrangement, Directed remote metalation (DreM), iterative DoM sequences, and DoM-halogen dance (HalD) synthetic strategies and has been transformed into a diverse range of functionalities and coupled with various groups through a range of cross-coupling (CC) strategies. Of ultimate value, the ArOAm group has demonstrated utility in the synthesis of a diverse range of bioactive and polycyclic aromatic compounds for various applications.

Photoredox-catalyzed coupling of aryl sulfonium salts with CO2 and amines to access O-aryl carbamates

An efficient photoredox-catalyzed three-component coupling reaction of aryl sulfonium salts, carbon dioxide and amines has been developed for the first time. This reaction provides a new strategy for the synthesis of a range of valuable O-aryl carbamates from readily available arenes via a site-selective thianthrenation/carbamoyloxylation two-step process. Mild conditions, broad substrate scope and good functional group tolerance are the features of the transformation. The synthetic utility of the method was demonstrated by the late-stage modification of bioactive molecules and pharmaceuticals.

C-H acylation of aniline derivatives with α-oxocarboxylic acids using ruthenium catalyst

An efficient and convenient synthetic strategy for ruthenium(II)-catalyzed ortho-acylation of N-(2-pyridyl)-anilines using α-oxycarboxylic acids as acyl sources is described. The procedure can smoothly proceed under mild conditions, showing good functional group tolerance. Valuable ortho-acylated aniline products have been obtained with moderate to good yields. Furthermore, the reaction could be easily scaled up to the gram scale.

Carbamates: A Directing Group for Selective C-H Amidation and Alkylation under Cp*Co(III) Catalysis

The selective reactivity of carbamate and thiocarbamate toward alkylation and amidation is reported under stable, high-valent, cost-effective cobalt(III) catalysis. This method reveals the wide possibility of designing a different branch of synthetically challenging yet highly promising asymmetric catalysts based on BINOL and SPINOL scaffolds. Late-stage C-H functionalization of l-tyrosine and estrone was also achieved through this approach. The mechanistic study shows that a base-assisted internal electrophilic substitution mechanism is operative here.

Palladium-Catalyzed Decarboxylative ortho-C(sp2 )-H Aroylation of N-Sulfoximine Benzamides at Room Temperature

A palladium-catalyzed method for the decarboxylative ortho C-H acylation of N-sulfoximine benzamides is developed at room temperature. The catalytic method enables easy access to various functionalized 2-aroylaromatic carboxylic acid derivatives in good isolated yields. Based on our mechanistic studies, a Pd(II)/Pd(IV) catalytic cycle that involves aroyl radical intermediate is proposed for the reaction.

Access to Biphenyls by Palladium-Catalyzed Oxidative Coupling of Phenyl Carbamates and Phenols

The oxidative cross-coupling of phenols (3 equiv) to various substituted phenyl N,N-diethylcarbamates was explored with a variety of substrates. Pd(OAc)2 was employed as the catalyst (20 mol%) and K2S2O8 as the stoichiometric oxidant in trifluoroacetic acid as the solvent (50 °C, 2 h). Carbamates without or with a substituent on the phenyl ring (Me, Ph, Cl, OMe) underwent the reaction unless the phenyl substituent was too strongly electron withdrawing (CN). Cross-coupling occurred exclusively in the ortho position relative to the carbamate group. The regioselectivity at the phenol (ortho or para to hydroxy) was mainly determined by steric factors. Yields up to 60–70% were achieved for specific carbamate/phenol combinations.

Decarboxylative acylation of N-free indoles enabled by a catalytic amount of copper catalyst and liquid-assisted grinding

A mechanochemically Cu(ii)-catalyzed decarboxylative acylation of N-free indoles with O₂ as a terminal oxidant was developed for the mild synthesis of 3-acylindoles.

Palladium-Catalyzed Decarboxylative ortho-Acylation of Anilines with Carbamate as a Removable Directing Group

An efficient palladium-catalyzed decarboxylative ortho-acylation of anilines with α-oxocarboxylic acids has been realized by using carbamate as a directing group (DG). The reaction proceeds smoothly with high regioselectivity to afford diverse acylation products of aniline derivatives in moderate to good yields under mild conditions. This transformation exhibits broad substrate scope and highly functional group tolerance. In addition, the employed DG can be easily removed to give the corresponding 2-amino aromatic ketones. Importantly, several transformations of the synthesized ortho-acylated anilines into several synthetically valuable products have been demonstrated for their utilities.

Palladium-catalyzed decarboxylative ortho-aroylation of N-acetyl-1,2,3,4-tetrahydroquinolines with α-oxoarylacetic acids

A mild and efficient palladium-catalyzed decarboxylative ortho-aroylation of N-acetyl-1,2,3,4-tetrahydroquinolines with α-oxoarylacetic acids via C–H bond activation is described. This protocol provides access to a series of C8-aroyl terahydroquinolines.

Acylation of Csp2–H bond with acyl sources derived from alkynes: Rh–Cu bimetallic catalyzed CC bond cleavage

Acylation of Csp²–H bond with acyl sources derived from alkynes: Rh–Cu bimetallic catalyzed CC bond cleavage.

β-Carboline-directed decarboxylative acylation of ortho-C(sp2)–H of the aryl ring of aryl(β-carbolin-1-yl)methanones with α-ketoacids under palladium catalysis

A Pd-catalysed β-carboline assisted decarboxylative acylation of ortho-C(sp²)–H of aryl ring of aryl(β-carbolin-1-yl)methanones using α-oxocarboxylic acid as the acyl ion source to form (2-aroylaryl)(β-carbolin-2-yl)methanones is demonstrated.

Formation of C(sp2)–S bonds through decarboxylation of α-oxocarboxylic acids with disulfides or thiophenols

Copper-catalyzed decarboxylative coupling between α-oxocarboxylic acids and diphenyl disulfides or thiophenols is presented, which provided an effective and direct approach for the preparation of useful thioesters through C(sp²)–S bond formation.

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.

Synthesis and C2-functionalization of indoles with allylic acetates under rhodium catalysis

Tandem rhodium-catalyzed oxidative allylation and annulation of acetanilides with allyl acetate to afford the corresponding indoles are described. In addition, the site-selective C2 allylation, crotylation and prenylation of indoles using allylic acetates under rhodium catalysis are reported.

Rh(III)-catalyzed oxidative coupling of 1,2-disubstituted arylhydrazines and olefins: a new strategy for 2,3-dihydro-1H-indazoles

A rhodium(III)-catalyzed oxidative olefination of 1,2-disubstituted arylhydrazines with alkenes via sp(2) C-H bond activation followed by an intramolecular aza-Michael reaction is described. This strategy allows the direct and efficient construction of highly substituted 2,3-dihydro-1H-indazole scaffolds.

A highly efficient palladium-catalyzed decarboxylative ortho-acylation of azobenzenes with α-oxocarboxylic acids: direct access to acylated azo compounds

Avoiding additives: A highly efficient and mild Pd-catalyzed decarboxylative ortho-acylation of azobenzenes with α-oxocarboxylic acids was developed that provides an alternative route to acylated azo compounds. This decarboxylative acylation process was completed in the absence of any additives at ambient temperature, to afford the acylated azobenzenes in moderate to good yields.