Rhodium-Catalyzed Directed Sulfenylation of Arene CH Bonds

Silver-catalyzed direct thiolation of quinones by activation of aryl disulfides to synthesize quinonyl aryl thioethers

A silver-catalyzed coupling reaction of quinones with aryl disulfides for the synthesis of quinonyl aryl thioethers is described. In the presence of AgOAc (0.2 equiv)/dppp (0.24 equiv) as the catalyst, (NH4)2S2O8 (3.0 equiv) as the oxidant, and Bu4NBF4 (1.0 equiv) as the additive, the reaction is simple, provides high yield (up to 88% yield), and possesses a broad substrate scope. The reaction is believed to proceed via direct activation of disulfides evidenced by observation of a metathesis reaction between two different disulfides placed together under the reaction conditions and (13)C NMR spectroscopy analysis.

Palladium(II)-catalyzed directed trifluoromethylthiolation of unactivated C(sp³)-H bonds

The synthesis of trifluoromethylthiolated aliphatic acid derivatives by Pd-catalyzed C(sp(3))-H bond functionalization was developed. Using a bidentate directing group, the direct and selective introduction of a SCF3 moiety was possible on a range of amides with remarkable selectivity for C(sp(3))-centers with an electrophilic SCF3 source and pivalic acid as an additive. This work constitutes an example of the unactivated C(sp(3))-SCF3 bond formation by C-H activation offering a new access to relevant molecules.

Rhodium-catalyzed C-H activation of phenacyl ammonium salts assisted by an oxidizing C-N bond: a combination of experimental and theoretical studies

Rh(III)-catalyzed C-H activation assisted by an oxidizing directing group has evolved to a mild and redox-economic strategy for the construction of heterocycles. Despite the success, these coupling systems are currently limited to cleavage of an oxidizing N-O or N-N bond. Cleavage of an oxidizing C-N bond, which allows for complementary carbocycle synthesis, is unprecedented. In this article, α-ammonium acetophenones with an oxidizing C-N bond have been designed as substrates for Rh(III)-catalyzed C-H activation under redox-neutral conditions. The coupling with α-diazo esters afforded benzocyclopentanones, and the coupling with unactivated alkenes such as styrenes and aliphatic olefins gave ortho-olefinated acetophenoes. In both systems the reactions proceeded with a broad scope, high efficiency, and functional group tolerance. Moreover, efficient one-pot coupling of diazo esters has been realized starting from α-bromoacetophenones and triethylamine. The reaction mechanism for the coupling with diazo esters has been studied by a combination of experimental and theoretical methods. In particular, three distinct mechanistic pathways have been scrutinized by DFT studies, which revealed that the C-H activation occurs via a C-bound enolate-assisted concerted metalation-deprotonation mechanism and is rate-limiting. In subsequent C-C formation steps, the lowest energy pathway involves two rhodium carbene species as key intermediates.

Late-stage diversification of biologically active pyridazinones via a direct C-H functionalization strategy

Divergent C-H functionalization reactions (arylation, carboxylation, olefination, thiolation, acetoxylation, halogenation, naphthylation) using a pyridazinone moiety as an internal directing group were successfully established. This approach offers a late-stage, ortho-selective diversification of a biologically active pyridazinone scaffold. Seven series of novel pyridazinone analogues were synthesized conveniently as the synthetic precursors of potential sortase A (SrtA) inhibitors.

Copper-mediated thiolation of carbazole derivatives and related N-heterocycle compounds

Cu-mediated direct thiolation of carbazole derivatives with disulfides via C–H bond cleavage to give diaryl and alkyl aryl sulfides which easily extends to the synthesis of thioethers with a benzo[h]quinolone, 2-phenylquinoline or indole moiety in satisfactory yields.

Manganese catalysed sulfenylation of N-methyl amides with arenesulfonyl hydrazides

A convenient oxidative sulfenylation method for the formation of various sulfenyl amides has been reported.

NiSO4-catalyzed C–H activation/C–S cross-coupling of 1,2,3-triazole N-oxides with thiols

An efficient nickel-catalyzed protocol for C–S cross-coupling through the direct functionalization of 2-aryl-1,2,3-triazole N-oxide C–H bonds with aryl or alkyl thiols, or diphenyl disulfide has been developed.

Nickel-catalyzed synthesis of diarylsulfides and sulfones via C–H bond functionalization of arylamides

The sulfenylation and sulfonylation of (sp²)C–H bonds of benzamides were achieved with the aid of a bidentate directing group.

Nickel-catalyzed and benzoic acid-promoted direct sulfenylation of unactivated arenes

A nickel-catalyzed direct sulfenylation of unactivated arenes using removable 2-(pyridine-2-yl)-isopropylamine as a directing group has been developed.

Nickel-catalyzed direct thiolation of unactivated C(sp3)–H bonds with disulfides

The first nickel-catalyzed thiolation of unactivated C(sp³)–H bonds with disulfides is described.

Recent advances in C–S bond formation via C–H bond functionalization and decarboxylation

The development of mild and general methods for C–S bond formation has received significant attention because the C–S bond is indispensable in many important biological and pharmaceutical compounds.

Nickel-catalyzed thiolation of unactivated aryl C–H bonds: efficient access to diverse aryl sulfides

A nickel-catalyzed thiolation of unactivated C(sp²)–H bonds with disulfides employing the PIP directing group was described. This process uses a catalytic nickel catalyst and no metallic oxidants or cocatalysts are required. Moreover, the reaction tolerates various important functional groups and heteroarenes.

A mild and facile synthesis of aryl and alkenyl sulfides via copper-catalyzed deborylthiolation of organoborons with thiosulfonates

A simple, efficient, and odorless deborylthiolation of aryl- and alkenylborons with thiosulfonates has been achieved under mild conditions using a copper catalyst.

Nickel-catalyzed directed sulfenylation of sp2 and sp3 C–H bonds

Directed sulfenylation of both sp² and sp³ C–H bonds was achieved through nickel catalyzed directed C–S bond formation, giving the desired product in good to excellent yield (up to 90%).

Rh(iii)- or Ir(iii)-catalyzed ynone synthesis from aldehydes via chelation-assisted C–H bond activation

A simple and practical synthesis of ynones directly from readily available aldehydes was developed for the first time under mild reaction conditions via a Rh(iii)- or Ir(iii)-catalyzed formyl C–H bond activation.

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.

Generation of ArS-substituted flavone derivatives using aryl thiols as sulfenylating agents

The regioselective and metal-free sulfenylation of flavones was achieved under aerobic conditions with ammonium iodide as an inducer.

Palladium-catalyzed direct thiolation of aryl C-H bonds with disulfides

A catalytic variant of the direct thiolation of arenes, bearing directing groups, with disulfides or thiols has been developed under palladium and copper co-catalysis. Both sulfenyl moieties of the disulfide could be incorporated into the thiolated products, therefore, the reactions reached completion with only half an equivalent of disulfide, with respect to the starting arene. Experimental evidence suggested that the reaction proceeds through a Pd(II)/Pd(IV) mechanism.

Silver-mediated oxidative vinylic C–H bond sulfenylation of enamides with disulfides

A silver-mediated oxidative vinylic C–H bond sulfenylation of enamides was developed. This method is compatible with diaryl and dialkyl disulfides to deliver the biologically precious chalcogenated olefins efficiently. A plausible non-chain radical mechanism was proposed for understanding this novel sulfenylation based on the mechanistic studies.