Palladium-Catalyzed Desulfitative Oxidative Coupling between Arenesulfinic Acid Salts and Allylic Alcohols: A Strategy for the Selective Construction of β-Aryl Ketones and Aldehydes

Palladium-Catalyzed Oxidative Nonclassical Heck Reaction of Arylhydrazines with Allylic Alcohols via C-N Bond Cleavage: Access to β-Arylated Carbonyl Compounds

An efficient palladium-catalyzed oxidative nonclassical Heck reaction of arylhydrazines with allylic alcohols via C-N bond cleavage has been successfully developed. This method provides a series of β-arylated carbonyl compounds with broad functional group tolerance under base-free, simple, and mild open air reaction conditions. In the reaction, arylhydrazines with the smaller molecular weight of the leaving group were employed as the "green" arylation reagent, which released N₂ and water as the byproducts under air. Mechanistic studies suggested that an aryl radical process and Pd-H complex migration reinsertion were involved. Moreover, the synthesis of the antiarrhythmic drug propafenone was completed with this transformation as the key step.

Homologation of aryl ketones to long-chain ketones and aldehydes via C-C bond cleavage

Transition metal-catalyzed C-C bond cleavage is a powerful tool for the reconstruction of a molecular skeleton. We report herein the multi-carbon homologation of aryl ketones to long-chain ketones and aldehydes via ligand-promoted Ar-C(O) bond cleavage and subsequent cross coupling with alkenols. Various (hetero)aryl ketones are compatible in the reaction, affording the corresponding products wtih good to excellent yields with high regioselectivity. Further applications in the late-stage diversification of biologically important molecules demonstrate the synthetic utility of this protocol. Mechanistic studies indicate that the ligand plays an important role in both C-C bond cleavage and the asymmetric migration-insertion process.

Bromine radical as a visible-light-mediated polarity-reversal catalyst

Polarity-reversal catalysts enable otherwise sluggish or completely ineffective reactions which are characterized by unfavorable polar effects between radicals and substrates. We herein disclose that when irradiated by visible light, bromine can behave as a polarity-reversal catalyst. Hydroacylation of vinyl arenes, a three-component cascade transformation and deuteration of aldehydes were each achieved in a metal-free manner without initiators by using inexpensive N-bromosuccinimide as the precatalyst. Light is essential to generate and maintain the active bromine radical during the reaction process. Another key to success is that HBr can behave as an effective hydrogen donor to turn over the catalytic cycles.

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Using bromine as a polarity-reversal catalyst to generate acyl radicals

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Additive- and metal-free, atom- and step-economic, and operationally simple process

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Using constant light-irradiation to induce and maintain bromine radicals

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Access carbonyl compounds and deuterated aldehydes with wide substrate scope

Direct conversion of secondary propargyl alcohols into 1,3-di-arylpropanone via DBU promoted redox isomerization and palladium assisted chemoselective hydrogenation in a single pot operation

Palladium(ii)acetate is found to be an efficient catalyst for the single-step conversion of secondary propargyl alcohols to 1,3-diarylpropanone derivatives under mild basic conditions.

Transition-metal mediated carbon-sulfur bond activation and transformations: an update

Carbon-sulfur bond cross-coupling has become more and more attractive as an alternative protocol to establish carbon-carbon and carbon-heteroatom bonds. Diverse transformations through transition-metal-catalyzed C-S bond activation and cleavage have recently been developed. This review summarizes the advances in transition-metal-catalyzed cross-coupling via carbon-sulfur bond activation and cleavage since late 2012 as an update of the critical review on the same topic published in early 2013 (Chem. Soc. Rev., 2013, 42, 599-621), which is presented by the categories of organosulfur compounds, that is, thioesters, thioethers including heteroaryl, aryl, vinyl, alkyl, and alkynyl sulfides, ketene dithioacetals, sulfoxides including DMSO, sulfones, sulfonyl chlorides, sulfinates, thiocyanates, sulfonium salts, sulfonyl hydrazides, sulfonates, thiophene-based compounds, and C[double bond, length as m-dash]S functionality-bearing compounds such as thioureas, thioamides, and carbon disulfide, as well as the mechanistic insights. An overview of C-S bond cleavage reactions with stoichiometric transition-metal reagents is briefly given. Theoretical studies on the reactivity of carbon-sulfur bonds by DFT calculations are also discussed.

An update on the use of sulfinate derivatives as versatile coupling partners in organic chemistry

The use of sulfinic acids and their salts continues to be extensively developed in organic chemistry. This is attributable to their dual capacity for acting as nucleophilic or electrophilic reagents, as well as their ease of preparation and stability on storage. This report highlights the research accomplished since 2015 on this topic, updating a previous review published by our team in 2014.

Copper-catalysed regioselective sulfenylation of indoles with sodium sulfinates

A copper-catalysed sulfenylation of indoles with sodium sulfinates that affords 3-sulfenylindoles in good-to-excellent yields in N,N-dimethyl formamide (DMF) is described. In the process, DMF serves not only as a solvent but also as a reductant. This transformation is easy to carry out and has mild reaction conditions and good functional group tolerance.

Halo-substituted benzenesulfonyls and benzenesulfinates: convenient sources of arenes in metal-catalyzed C–C bond formation reactions for the straightforward access to halo-substituted arenes

The use of halo-substituted ArSO₂R as an aryl source in metal-catalyzed C–C bond formation reactions presents several advantages, as the reaction often proceeds without cleavage of the C–halo bonds.

Regiocontrolled Synthesis of α-Sulfonylmethyl o-Nitrostyrenes via ZnI2-Mediated Sulfonylation and AgNO2/Pd(PPh3)4-Promoted o-Nitration

We report herein the AgNO₂/Pd(PPh₃)₄-promoted regiocontrolled o-nitration of α-sulfonylmethylstyrenes in MeNO₂ with good yields. The o-nitration process provides a series of sulfonyl o-nitrostyrenes. Substituted α-sulfonylmethylstyrenes were synthesized from ZnI₂-mediated sulfonylation of substituted α-methylstyrenes and sodium sulfinates (RSO₂Na) in MeCN with good to excellent yields. The structures of the key products were confirmed by X-ray crystallography. A plausible mechanism has been proposed herein.

Pd-catalyzed desulfitative arylation for the synthesis of 2,5-diarylated oxazole-4-carboxylates using dioxygen as the terminal oxidant

A novel palladium-catalyzed approach for constructing 2,5-diarylated oxazole-4-carboxylates using sodium arylsulfinates as the aryl source has been demonstrated.

Directed C–C bond cleavage of a cyclopropane intermediate generated fromN-tosylhydrazones and stable enaminones: expedient synthesis of functionalized 1,4-ketoaldehydes

An efficient method to construct functionalized 1,4-ketoaldehydes bearing all-carbon α-quaternary centersviaregioselective C–C bond activation has been described.

Palladium-catalyzed C-3 desulfitative arylation of indolizines with sodium arylsulfinates and arylsulfonyl hydrazides

Derivatized indolizines were efficiently prepared by direct C-3 arylation of indolizines using sodium arylsulfinates and arylsulfonyl hydrazides in good yields.