Palladium nanoparticles as efficient catalyst for C–S bond formation reactions

The development of green, economical and sustainable chemical processes is one of the primary challenges in organic synthesis. Herein, we report an efficient and heterogeneous palladium-catalyzed sulfonylation of vinyl cyclic carbonates with sodium sulfinates via decarboxylative cross-coupling. Both aliphatic and aromatic sulfinate salts react with various vinyl cyclic carbonates to deliver the desired allylic sulfones featuring tri- and even tetrasubstituted olefin scaffolds in high yields with excellent selectivity. The process needs only 2 mol% of Pd₂(dba)₃ and the in situ formed palladium nano-particles are found to be the active catalyst.

Heterogenous catalysis: economical and sustainable synthesis of allylic sulfone featuring tri- and even tetrasubstituted olefin scaffold via decarboxylative cross-coupling from vinyl cyclic carbonates with sodium sulfinates using PdNPs as a catalyst.     

Electrochemical sulfonylation of alkenes with sulfonyl hydrazides: a metal- and oxidant-free protocol for the synthesis of (E)-vinyl sulfones in water

An efficient electrochemical transformation of a variety of alkenes and sulfonyl hydrazides into vinyl sulfones with a catalytic amount of tetrabutylammonium iodide in water is reported. The reaction proceeds smoothly to afford vinyl sulfones with good selectivities and yields at room temperature under air in an undivided cell. Cyclic voltammograms and control experiments have been performed to provide preliminary insight into the reaction mechanism. The key features of this reaction include using pure water as solvent, transition metal- and oxidant-free conditions, and being easily scaled up to gram-scale synthesis.

An electrochemical sulfonylation of alkenes with sulfonyl hydrazides for the synthesis of (E)-vinyl sulfones in water is reported.     

Synthesis of spirocyclic Δ4-isoxazolines via [3 + 2] cycloaddition of indanone-derived ketonitrones with alkynes

A [3 + 2] cycloaddition of indanone-derived nitrones and alkynes under mild conditions is developed, allowing facile synthesis of spirocyclicindenyl isoxazolines with structural diversity. The sequential protocol of generated in situ ketonitrone from unsaturated ketones and N-alkylhydroxylamines is also achieved successfully, affording the desired products in considerable yield with moderate to good diastereoselectivity. Moreover, the spirocyclic product can be conveniently transformed into indenyl-based allylic alcohol and enamide.

A [3 + 2] cycloaddition of indanone-derived nitrones with alkynes under mild conditions has been developed. It is a highly efficient and straightforward method for the synthesis of diverse spirocyclicindenyl isoxazolines.     

Visible-light-induced one-pot synthesis of sulfonic esters via multicomponent reaction of arylazo sulfones and alcohols

Sulfonic ester is a chemical structure common to many organic molecules, including biologically active compounds. Herein, a visible-light-induced synthetic method to prepare aryl sulfonic ester from arylazo sulfones was developed. In the present study, a one-pot reaction was carried out using arylazo sulfones, DABSO (DABCO·(SO₂)₂), and alcohols in the presence of CuI as a coupling catalyst and HCl as an additive to yield sulfonic esters via multicomponent reaction. This synthetic method afforded a wide range of sulfonic esters with high yields under mild conditions.

Facile and efficient one-pot synthesis of sulfonic esters has been achieved via visible-light-induced multicomponent reaction of arylazo sulfones, and alcohols in the presence of DABSO, CuI, and HCI.     

Highly efficient synthesis of 3,4-diarylbutadiene sulfones using Heck–Matsuda reaction

For the first time we describe a general method for the synthesis of previously not synthesized unsymmetrical 3,4-diarylbutadiene sulfones which can be stable convenient precursors for 2,3-diaryl-1,3-butadienes. Our method for arylation of butadiene sulfones via Heck–Matsuda reaction allows to obtain unsymmetrical 3,4-diarylbutadiene sulfones with a variety of alkyl, alkoxy, nitro, ethoxycarbonyl, perfluoroalkyl and halogen substituents (30 examples) in very good yields using readily available reagents and catalysts.

An efficient and facile Pd-catalyzed synthesis of 3,4-diarylbutadiene sulfones with high regioselectivity from aryldiazonium salts and butadiene sulfone was developed.     

Photooxidation of thiosaccharides mediated by sensitizers in aerobic and environmentally friendly conditions

A series of β-d-glucopyranosyl derivates have been synthesized and evaluated in photooxidation reactions promoted by visible light and mediated by organic dyes under aerobic conditions. Among the different photocatalysts employed, tetra-O-acetyl riboflavin afforded chemoselectively the respective sulfoxides, without over-oxidation to sulfones, in good to excellent yields and short reaction times. This new methodology for the preparation of synthetically useful glycosyl sulfoxides constitutes a catalytic, efficient, economical, and environmentally friendly oxidation process not reported so far for carbohydrates.

An environmentally friendly and simple sensitized photooxidation methodology to obtain glycosyl sulfoxides with outstanding chemoselectivity in aerobic conditions is described.     

One-pot synthesis of symmetric imidazolium ionic liquids N,N-disubstituted with long alkyl chains

The Debus–Radziszewski imidazole synthesis was adapted to directly yield long-chain imidazolium ionic liquids. Imidazolium acetate ionic liquids with side-chains up to sixteen carbon atoms were synthesised in excellent yields via an on-water, one-pot reaction. The imidazolium acetate ILs acted as surfactants when dissolved in various solvents. The imidazolium acetate ionic liquids were also derivatised via an acid metathesis to the chloride, nitrate, and hydrogen oxalate derivatives. The thermal behaviour of all the ionic liquids was determined via thermogravimetric and calorimetric analysis.

The modified Debus–Radziszewski reaction was used as a one-pot on-water reaction to allow a greener synthesis of long-chain 1,3-dialkylimidazolium acetate ionic liquids in high yield from long-chain linear amines.     

A slight bluish-white fluorescence from E,E-2,6-bis(4-cyanostyryl)pyridine pristine crystals

Among various light emission phenomena, multicolour light emission, such as white light emission, is an interesting phenomenon. Bis-styrylbenzene derivatives show unique and excellent emission behaviours. In this study, three types of bis-styrene derivatives, with thiophene, pyridine, and benzene rings at the central position, were synthesised, and their photophysical properties were studied in detail. Among them, pristine crystals of E,E-2,6-bis(4-cyanostyryl)pyridine (Py4CN) showed a slight bluish-white emission because the Py4CN pristine crystals were mixtures of two separate crystals emitting blue and yellow-green fluorescence.

E,E-2,6-Bis(4-cyanostyryl)pyridine pristine crystals showed slightly bluish white emission: these were mixtures of two crystals emitting blue and yellow-green regions.     

Copper-catalyzed chemoselective synthesis of 4-trifluoromethyl pyrazoles

A series of 4-trifluoromethyl pyrazoles have been prepared via the copper-catalyzed cycloaddition of 2-bromo-3,3,3-trifluoropropene with a variety of N-arylsydnone derivatives under mild conditions. This new protocol under optimized reaction conditions [Cu(OTf)₂/phen, DBU, CH₃CN, 35 °C] afforded 4-trifluoromethyl pyrazoles in moderate to excellent yields with excellent regioselectivity.

A copper-catalyzed chemoselective synthesis of 4-trifluoromethyl pyrazoles via cycloaddition of 2-bromo-3,3,3-trifluoropropene with N-arylsydnones has been developed.     

Palladium-catalyzed tandem allylic substitution/cyclization and cascade hydrosilylated reduction: the influence of reaction parameters and hydrosilanes on the stereoselectivity

To shed light on the influence of reaction parameters on palladium-catalyzed tandem allylic alkylation in the presence of Fei-Phos (a chiral trans-1,2-diaminocyclohexane-derived phosphine ligand), the effect of different phosphine ligands, inorganic or organic bases, Brønsted acids, and other additives on the asymmetric palladium-catalysed alkylation of catechol with allylic diacetate was investigated. In this reaction, 2-vinyl-2,3-dihydro-benzo[1,4]dioxin products with promising enantioselectivity were achieved in good yields. In addition, a novel palladium-catalyzed three-component and one-pot allylic substitution/cyclization/reduction reaction assisted by methylphenylsilane was reported with good selectivity.

Pd-catalyzed AAA of 1,2-bifunctional nucleophiles and one-pot tandem allylic cyclization/reduction gave corresponding heterocycle products with promising enantioselectivity in good yields.     

Copper-catalyzed C–H acyloxylation of 2-phenylpyridine using oxygen as the oxidant

An efficient copper-catalyzed direct o-acyloxylation of 2-phenylpyridine with carboxylic acids using oxygen as the oxidant has been developed. Various acids including aromatic acids, cinnamic acids and aliphatic acids are effective acyloxylation reagents and provide the desired products in moderate to excellent yields. The reaction proceeds well under an oxygen atmosphere, making this method potentially practical.

A copper catalyzed direct o-acyloxylation of 2-phenylpyridine with various carboxylic acids using oxygen as oxidant has been developed.     

Visible light enabled [4+2] annulation reactions for anthracenone-furans from 2,3-dibromonaphthoquinone and phenylbenzofurans

A facile visible light promoted approach to anthracenone-furans from readily available 2,3-dibromonaphthoquinones and phenylbenzofurans via a formal Diels Alder reaction is reported. This reaction involves wavelength-selective agitation of 4CzIPN, energy transfer to quinones, recombination of 1,6-biradicals and elimination to give anthracenone-furans in good to excellent yields in one pot.

A facile visible light promoted [4 + 2] annulation reaction from readily available starting materials using an organo-photocatalyst gave anthracenone-furans with up to 95% yield in one-pot.     

Benzyl thioether formation merging copper catalysis

A novel copper-catalyzed thioetherification reaction has been developed to afford benzyl thioethers in moderate to excellent yields. Under the mild and easy-to-operate conditions, a variety of thioethers are efficiently prepared from readily available benzyl alcohols (primary, secondary, and tertiary) and thiols in the presence of Cu(OTf)₂ as the Lewis acid catalysis. This C–S bond formation protocol furnishes exceptional chemoselectivity, and the preliminary mechanism studies show that the reaction should proceed through a Lewis-acid-mediated S_N1-type nucleophilic attack of the carbocations formed in situ.

A novel copper-catalyzed thioetherification reaction has been developed to afford benzyl thioethers in moderate to excellent yields.     

Asymmetric vinylogous aldol addition of alkylidene oxindoles on trifluoromethyl-α,β-unsaturated ketones

A novel vinylogous aldol addition of alkylidene oxindole with 1-trifluoromethyl-3-alkylidene-propan-2-ones is presented. The reaction, catalyzed by a bifunctional tertiary amine, provides an efficient application of the vinylogous reactivity of oxindoles for the preparation of enantioenriched trifluoromethylated allylic alcohols.

The vinylogous aldol addition of alkylidene oxindole with 1-trifluoromethyl-3-alkylidene-propan-2-ones was developed. The reaction, provides straightforward access to enantioenriched trifluoromethylated allylic alcohols.     

Synthesis and antitumor effects of novel benzyl naphthyl sulfoxide/sulfone derivatives derived from Rigosertib

In this work, a series of novel benzyl naphthyl sulfoxides/sulfones derived from Rigosertib were designed and synthesized as potential antitumor agents. The in vitro cytotoxicity against four human cancer cell lines (HeLa, MCF-7, HepG2 and SCC-15) and two normal human cell lines (HUVEC and 293T) indicated that some of the sulfones and sulfoxides possessed potent antineoplastic activity that reached nanomolar levels and relatively low toxicity to normal cells. Among them, (2-methoxy-5-((naphthalen-2-ylsulfonyl)methyl)phenyl)glycine (15b) was found to be a promising antitumor drug candidate that could significantly inhibit tumor cell migration and induce tumor cell apoptosis via the p53-Bcl-2-Bax signaling pathway at nanomolar concentrations.

In this work, a series of novel benzyl naphthyl sulfoxides/sulfones derived from Rigosertib were designed and synthesized as potential antitumor agents.     

Enantioselective Michael addition of malonates to α,β-unsaturated ketones catalyzed by 1,2-diphenylethanediamine

A general and highly enantioselective Michael addition of malonates to cinnamones and chalcones has been developed. The commercially available 1,2-diphenylethanediamine could be directly utilized as the organocatalyst to furnish the desired adducts in satisfactory yield (61–99%) and moderate to excellent enantiopurity (65 to >99% ee). β-Ketoester was also a competent donor and was employed to construct densely functionalized cyclohexenones via a tandem Michael-aldol condensation process.

1,2-Diphenylethanediamine could be directly utilized to promote the Michael addition of malonates and β-ketoesters to various α,β-unsaturated ketones.     

Iridium-catalyzed ortho-selective carbon–hydrogen amidation of benzamides with sulfonyl azides in ionic liquid

An efficient and convenient iridium(iii) catalyzed ortho-C–H bond amidation of weakly coordinating benzamides treated with readily available sulfonyl azides as the amino source has been described. In this transformation, ionic liquids represents an ideal reaction medium, giving rise to a broad range of amidation products under mild conditions in the open air. This protocol offers moderate to excellent chemical yields, exclusive regioselectivities, and good functional group tolerance.

Ir-catalyzed ortho-C–H amidation of benzamides with sulfonyl azides has been conducted effectively in ionic liquid reaction medium.     

TBAI-assisted direct C–H activation of indoles with β-E-styrene sulfonyl hydrazides: a stereoselective access to 3-styryl thioindoles

The current work describes the challenging introduction of a vinyl sulfide group by simple C–H activation on a variety of substrates. The direct C–H activation of indoles with β-(E)-styrene sulfonyl hydrazides under the sulfenylation conditions, assisted by the iodic catalyst tert-butyl ammonium iodide (TBAI), afforded a series of (E)-styrylthioindoles. Accordingly, β-(E)-styrene sulfonyl hydrazides undergo radical cross-coupling reactions with a variety of substituted indoles to afford structurally diverse indole vinyl thioethers in moderate to high yields with E-stereoselectivity. This method is metal-catalyst-free and is valuable not only because of its novelty, but also for providing a convenient synthetic pathway to a variety of (E)-styrylthioindoles with retention of the configuration. The current study paves the way for the use of β-(E)-styrene sulfonyl hydrazides as a unique styryl mercaptan source in chemical synthesis.

Direct C–H activation of indoles with beta-(E)-styrene sulfonyl hydrazides assisted by TBAI afforded structurally diverse indole vinyl thioethers in moderate to high yields with E-stereoselectivity.     

The synthesis of imidazo[1,5-a]quinolines via a decarboxylative cyclization under metal-free conditions

An iodine-mediated decarboxylative cyclization was developed from α-amino acids and 2-methyl quinolines under metal-free conditions, affording a variety of imidazo[1,5-a]quinolines with moderate to good yields.

An iodine-mediated decarboxylative cyclization was developed from α-amino acids and 2-methyl quinolines under metal-free conditions, affording a variety of imidazo[1,5-a]quinolines with moderate to good yields.     

MIDA boronate allylation – synthesis of ibuprofen

MIDA boronates are among the most useful reagents for the Suzuki–Miyaura reaction. This chemistry typically generates new bonds between two aromatic rings, thereby restricting access to important areas of chemical space. Here we demonstrate the coupling of MIDA boronates to allylic electrophiles, including a new synthesis of the well-known COX inhibitor ibuprofen.

Here we demonstrate the coupling of MIDA boronates to allylic electrophiles, including a new synthesis of the well-known COX inhibitor ibuprofen.