Search

The Rh-catalyzed cyclization of indolinones (I) with symmetrical alkynes (II) leads to pseudo-indoxyls (III) in moderate to high yields.

The operationally simple and atom-economical reaction allows for the regio- and diastereoselective formation of four bonds, thus offering a powerful strategy toward polycyclic skeletons with potential biological activity.

The domino reaction of ester-substituted Morita—Baylis—Hillman carbonates (I) with α-cyano-α,β-unsaturated ketones (II) and (IV) proceeds via α-selective cyclopropanation, ring-opening, and ring-closure cascade reactions to afford chiral tetrahydrofuropyranoindoles (III) and (V), respectively.

The first example of Cu-promoted cyclization of α-amino nitrile-tethered enynes incorporating an electron-deficient alkene component is described. A wide range of functionalized 3-azabicyclo[4.1.0]hepta-2,4-dienes and 4,5-dihydro-3H-azepines were prepared efficiently in a controllable manner. Moreover, the diverse cascade process enables efficient incorporation of tertiary amine moieties under mild reaction conditions. A possible reaction pathway is proposed on the basis of a series of control experiments.

Iodination of areneboronic acids by perfluoroisopropyl iodide in the presence of Cu powder gives aryl iodides in high yields, while with cupric acetate perfluoroalkylation occurs to provide perfluoroisopropyl arenes in acceptable to moderate yields.

A novel cinchona-alkaloid-derived organocatalyst has been developed to catalyze the asymmetric regioselective [3+2] cycloaddition of 3-isothiocyanato oxindoles with dibenzylidene ketones. A series of spirooxindole enols could be obtained in high yields with good-to-excellent diastereo- and enantioselectivities.

A copper-catalyzed transfer aldol type reaction of β-hydroxy ketones or nitriles with aldehydes is reported, which enables chemo- and stereoselective access to (E)-α,β-unsaturated ketones and (E)-acrylonitriles. A key step of the in situ copper(I)-promoted retro-aldol reaction of β-hydroxy ketones or nitriles is proposed to generate a reactive Cu(I) enolate or cyanomethyl intermediate, which undergoes ensuing aldol condensation with aldehydes to deliver the products. This reaction uses 1.2 mol% Cu(IPr)Cl (IPr denotes 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) as the catalyst in the presence of 6.0 mol% NaOtBu cocatalyst at room temperature or 70 °C. A range of aryl and heteroaryl aldehydes as well as acrylaldehydes are compatible with many useful functional groups being tolerated. Under the mild and weakly basic conditions, competitive Cannizzaro-type reaction of benzaldehydes and side reactions of base-sensitive functional groups can be effectively suppressed, which show synthetic advantages of this reaction compared to classic aldol reactions. The synthetic potential of this reaction is further demonstrated by the one-step synthesis of biologically active quinolines and 1,8-naphthyridine in excellent yields (up to 91%). Finally, a full catalytic cycle for this reaction has been constructed using DFT computational studies in the context of a retro-aldol/aldol two-stage mechanism. A rather flat reaction energy profile is found indicating that both stages are kinetically facile, which is consistent with the mild reaction conditions.

Two novel aporphine related alkaloids, fissitungfines A ( 1 ) and B ( 2 ), together with two known biogenetically related alkaloids, nornuciferine ( 3 ) and annonaine ( 4 ), were isolated from the stems of Fissistigma tungfangense . Fissitungfines A ( 1 ) and B ( 2 ) were a new type of aporphine related alkaloids, possessing an unprecedented skeleton in which one six-membered carbocyclic ring in classic aporphine alkaloid was replaced by one six-membered lactone ring. Their structures were elucidated on the basis of spectroscopic data. A plausible biogenetic pathway for this new type of aporphine related alkaloid is also proposed.

A one-pot sequential asymmetric hydrogenation of β-aryl-β-aryloxy acroleins has been realized for the preparation of chiral 3-aryl-3-aryloxy alcohols with excellent yields and good enantioselectivities. This methodology can be employed in new synthetic routes for the synthesis of fluoxetine, atomoxetine, and related analogues.

The 1,4-diazabicyclo[2.2.2]octane (DABCO) catalyzed divergent [3+2] annulation of C,N-cyclic azomethine imines with δ-acetoxyallenoates was developed; 5,6-dihydropyrazolo[5,1-a]isoquinolines and ethyl (Z)-3-acetoxy-3-tosylpent-4-enoates were afforded in moderate to good yields in a one-pot manner under mild conditions. This annulation reaction provides a highly efficient method to construct dinitrogen-fused heterocycles and ethyl (Z)-3-acetoxy-3-tosylpent-4-enoates at the same time.

There are many reports on long persistent phosphors (LPPs) applied in bioimaging. However, there are few reports on LPPs applied in photothermal therapy (PTT), and an integrated system with multiple functions of diagnosis and therapy. In this work, we fabricate effective multifunctional phosphors Zn3 Ga2 SnO8 : Cr(3+) , Nd(3+) , Gd(3+) with NIR persistent phosphorescence, photothermal response and magnetism. Such featured materials can act as NIR optical biolabels and magnetic resonance imaging (MRI) contrast agents for tracking the early cancer cells, but also as photothermal therapeutic agent for killing the cancer cells. This new multifunctional biomaterial is expected to open a new possibility of setting up an advanced imaging-guided therapy system featuring a high resolution for bioimaging and low side effects for the photothermal ablation of tumors.

A tetraphosphoramidite ligand was successfully applied to a Rh-catalyzed hydroformylation of various symmetrical and unsymmetrical alkynes to afford corresponding α,β-unsaturated aldehyde products in good to excellent yields (up to 97% yield). Excellent chemo- and regioselectivities and high activities (up to 20 000 TON) were achieved. The corresponding α,β-unsaturated aldehyde products can be transformed into many useful and important organic molecules, such as indenamine derivatives and lukianol pyrroles. This great performance makes the hydroformylation of alkynes highly practical with great potential.

Under mild reaction conditions, the tandem cycloadditions of cyclic N-sulfonylimines with in situ generated Huisgen 1,4-dipoles from dialkyl acetylenedicarboxylates and pyridines underwent readily, and delivered highly functionalized polycyclic 1,2,3,4-tetrahydropyrimidine-fused benzosultams in low to excellent chemical yields with excellent diastereoselectivities.

A new method for the synthesis of di- and trisubstituted pyrroles via copper-catalyzed cyclization of ethyl allenoates with activated isocyanides has been developed. In contrast to related annulation reactions previously reported, this new process features a skeletal rearrangement in which the aryl sulfonyl moiety, which functions as the electron-withdrawing group in the α-carbon of the isocyanide, was found to migrate to the γ-carbon of the starting allenoate in the final product for the first time.

The enantioselective N-heterocyclic carbene-catalyzed [2 + 4] cyclocondensation of α-chloroaldehydes and saccharine-derived 1-azadienes was developed, giving the corresponding saccharine-derived dihydropyridinones in good yields with exclusive cis-selectivities and excellent enantioselectivities.

A transformation analogous in simplicity and functional group tolerance to the venerable Suzuki cross-coupling between alkyl-carboxylic acids and boronic acids is described. This Ni-catalyzed reaction relies upon the activation of alkyl carboxylic acids as their redox-active ester derivatives, specifically N-hydroxy-tetrachlorophthalimide (TCNHPI), and proceeds in a practical and scalable fashion. The inexpensive nature of the reaction components (NiCl2 ⋅6 H2 O-$9.5 mol(-1) , Et3 N) coupled to the virtually unlimited commercial catalog of available starting materials bodes well for its rapid adoption.

A novel and convenient palladium-initiated radical cascade stereoselective iodofluoroalkylation/cycloisomerization of ene-vinylidenecyclopropanes with fluoroalkyl iodides has been developed. The reaction proceeds under mild reaction conditions with high atom economy and stereoselectivity, thereby allowing an efficient access to a variety of difluoromethylated or perfluoroalkylated pyrrolidines tethered with an alkyl iodide. Two plausible radical pathways for the transformation have been proposed on the basis of the results of control experiments and previous reports, which in one case it was thought that palladium(0) was an initiator rather than a catalyst.

A practical and efficient synthesis of 3-trifluoromethyl functionalized indoles was successfully developed via Rh-catalyzed oxidative cross-coupling/annulations of readily available acetanilides with trifluoromethylated internal alkynes. Good yields and functional group tolerance as well as excellent regioselectivities were achieved under mild reaction conditions.

Hydroaminomethylation is a perfect reaction for converting alkenes into valuable amines with high atom economy in the presence of the syngas and amines. Significant progress has been made in the past decades; however, there still remain challenges for the control of chemo- and regioselectivity concurrently. Rhodium has proved to be a better metal in hydroaminomethylation for higher activity in hydroformylation and hydrogenation steps. Although promising results were shown by unmodified rhodium catalysts, phosphine ligand modified rhodium complexes generally displayed better activity and regioselectivity. Among the phosphorus ligands developed, tetraphosphorus ligands exhibited much better regioselectivity due to their stronger chelating ability. Apart from the phosphorus ligands, carbene and nitrogen-containing ligands have also been developed which showed good activity due to the promotion of the hydrogenation step. Although non-enantioselective hydroaminomethylation reactions have been intensively studied, reports on asymmetric hydroaminomethylation are rare. Direct asymmetric hydroaminomethylation is very challenging and only reaction systems with two different catalysts showed promising results.

Total synthesis of (±)-Lingzhilactone B has been achieved for the first time in 13 steps. The key step features a semipinacol rearrangement to construct 5/5 bicyclic ring with adjacent quaternary carbon.

A novel rhodium-catalyzed/copper-mediated C2-selective C−H alkynylation of indoles using γ-substituted tert-propargyl alcohols as the alkynylating reagent and a removable 6-methylpyridin-2-yl as the directing group has been developed, which provides a viable pathway for direct C2-selective alkynylation of indoles. Moreover, this strategy could be extended to the C−H alkynylation of carbazoles at the C1 position.

A series of tridentate ferrocene aminophosphoxazoline ligands like APX is synthesized and successfully applied to the asymmetric hydrogenation of ketones.

The synthesis of privileged structures, which are potent drug candidates, is an impetus for drug discovery. The construction of heterocyclic framework furo[3,2-c]coumarins using a visible-light promoted photoredox neutral coupling of 3-bromo-4-hydroxycoumarins with commercially available alkynes has been reported. These reactions can be carried out at room temperature under visible light irradiation with good chemical yields. This work presents 17 furocoumarins, 12 of which are new. Three of the newly synthesized compounds show potent cytotoxicity, and one shows moderate acetylcholinesterase inhibitory activity with IC50 values of 2.16 ± 0.13 μM.

Pd-catalyzed Suzuki cross-coupling reactions between arylboronic acids and bromoarenes is applied in the synthesis of liquid-crystalline materials.

A series of deep eutectic solvents (DESs) based on choline chloride were prepared and used in the Morita–Baylis–Hillman (M–B–H) reaction. Research showed that the composite solvent (1ChCl/2Gly DES–H2O) is a very effective solvent media for all substrates tested. Under the mild reaction conditions, DABCO catalyzed M–B–H reactions proceed very quickly and efficiently. It is particularly important that the solid M–B–H adducts suspended in the reaction system at the end of the reaction, which can be obtained by simple filtering. Such simple product processing is not reported in the previous literature. The composite solvent (1ChCl/2Gly DES–H2O) was reused directly without any activation process. After six cycles, the yields almost remained unchanged. This protocol has notable advantages such as low cost, ease of work-up and reuse of DES conveniently, which could contribute to the development of new solvent system for use in continuous chemical processes.

Polycrystalline samples of the title thermoelectric solid solution of title (x = 0—0.5, δ = 0.02—0.05) are prepared by melting and annealing stoichiometric amounts of the elements (graphite crucible in evacuated silica tubes, 1.

The bifunctional N-heterocyclic carbene catalyzed [3 + 4] annulation of enals and 5-alkenyl thiazolones was developed, giving the corresponding thiazole-fused e-lactones in high yields with excellent diastereoselectivties and enantioselectivities. The thiazole-fused e-lactone could be isomerized to the spirocyclic thiazolone–cyclopentanone without erosion of enantioselectivity.

This review focuses on the most recent advances in the field of transition-metal-catalyzed direct intermolecular C−H amidation and amination of arenes. The manuscript is divided into two parts according to whether or not external oxidants are required. The first part includes the cases of simple neutral amines, amides, or sulfonamides in combination with external oxidants. The second section contains the examples of preactivated amino sources in the absence of any external oxidants. In each part, the content is classified in line with the different types of transition-metal catalysts used, including Rh, Ru, Ir, Pd, Cu, Ni, Co, and Fe. In addition, the substrate scope and limitations as well as catalytic mechanism are discussed.

An effective synthetic protocol for structurally diverse 4-acyloxy-1,2-dihydroquinoline compounds has been accomplished by a gold(I)-catalyzed tandem [3,3]-rearrangement and intramolecular hydroamination of propargylic esters, affording the desired products in good yields. Moreover, the asymmetric variant of this cyclization has also been achieved using a chiral nitrogen acyclic carbene (NAC) gold(I) complex. These products have application in the enantioselective synthesis of an aromatase inhibitor within three simple steps.

Alkyl carboxylic acids are ubiquitous in all facets of chemical science, from natural products to polymers, and represent an ideal starting material with which to forge new connections. This study demonstrates how the same activating principles used for decades to make simple C–N (amide) bonds from carboxylic acids with loss of water can be used to make C–C bonds through coupling with dialkylzinc reagents and loss of carbon dioxide. This disconnection strategy benefits from the use of a simple, inexpensive nickel catalyst and exhibits a remarkably broad scope across a range of substrates (>70 examples).

Silver-mediated direct trifluoromethoxylation of α-diazo esters and ketosteroid was disclosed. The reactions of alkyl α-diazo arylacetates with AgOCF3 or CF3SO2OCF3/AgF at −30 to 10 °C under a N2 atmosphere provided α-trifluoromethoxyl arylacetates in up to 90% yield, while alkyl α-diazo vinylacetates reacting with CF3SO2OCF3/AgF or AgOCF3 afforded γ-trifluoromethoxyl α,β-unsaturated esters in up to 94% yield. The α-diazo ketosteroid was also trifluoromethoxylated under the standard reaction conditions. This protocol allows for an effective and convenient access to a large number of synthetic building blocks, which are promising in the development of new functional OCF3-molecules.

A Pd-catalyzed Suzuki cross-coupling of arylboronic acids with Yagupolskii-Umemoto reagents was explored. In contrary to trifluoromethylations, the Pd-catalyzed reaction of R-B(OH)2 and [Ar2 SCF3 ](+) [OTf](-) provided the arylation products (R-Ar) in good to high yields. The reaction confirms that the S-Ar bonds of [Ar2 SCF3 ](+) [OTf](-) can be readily cleaved in the presence of Pd complexes. The relatively electron-poor aryl groups of asymmetric [Ar(1) Ar(2) SCF3 ](+) [OTf](-) salts are more favorably transferred compared to the electron-rich ones. This reaction represents the first report of utilization of [Ar2 SCF3 ](+) [OTf](-) as arylation reagents in organic synthesis.

A novel stereoselective Michael cyclization reaction of cyclic methyleneindolinones and 3-isothiocyanatooxindoles is presented furnishing chiral trispirooxindoles in good yield and enantioselectivities.

The highly enantioselective synthesis of dihydroisoquinoline derivatives from aromatic sulfonated imines tethered with an alkyne moiety, through a one-pot asymmetric relay catalysis of chiral-phosphine and gold catalysts, is reported. Enantiomerically enriched dihydroisoquinoline derivatives were afforded in good yields and good-to-excellent ee values under mild conditions, based on the asymmetric aza-Morita-Baylis-Hillman reaction. Dihydroisoquinoline derivatives containing two chiral centers were also synthesized through further transformations.

A new formal [3 + 1]-cycloaddition reaction of azaoxyallyl cation intermediates, generated in situ from α-halo hydroxamates bearing α-alkyl groups, and sulfur ylides is reported, furnishing useful β-lactams (dr >19:1) in fair to modest yields. In contrast, an unexpected formal [3 + 2]-cycloaddition reaction occurs to give γ-lactam derivatives for α-halo hydroxamates with α-aryl groups and sulfur ylides in the presence of bases.

2-Hydroxyethylammonium acetate ionic liquid was found to be an excellent catalyst for the one-pot synthesis of 1,4-dihydropyridine derivatives via Hantzsch reaction of ethyl acetoacetate or acetoacetanilide, ammonium acetate, and various aromatic aldehydes. The combinatorial syntheses were achieved for the first time using 2-hydroxyethylammonium acetate ionic liquid as a homogeneous catalyst. The catalyst was active for the Hantzsch reaction in alcohol at reflux. The products were isolated in good yields (78–93 %). The resulting substituted dihydropyridines were characterized and confirmed by1H NMR spectral data. The catalyst offers simple means for recovery and the isolated catalyst was reused for three rounds for the synthesis without significant loss of catalytic activity. For all the other reactions carried out with the recycled catalyst, results were similar to that with the fresh catalyst.

A phosphine-catalyzed (4 + 1) annulation reaction of o-hydroxyphenyl and o-aminophenyl ketones with ester-modified allylic carbonates has been developed, providing a facile and efficient method to synthesize functionalized 2,3-disubstituted dihydrobenzofurans and indolines. Under mild conditions and in the catalysis of PPh3 (20 mol %), the reactions of o-hydroxyphenyl or o-aminophenyl ketones readily furnish highly functionalized 3-hydroxy-2,3-disubstituted dihydrobenzofurans or 3-hydroxy-2,3-disubstituted indolines in 40–99% yields with generally high diastereoselectivity. To further expand the utility of this annulation reaction to the synthesis of functionalized benzofurans and indoles, the CuSO4-promoted chemical transformations of the annulation products have also been studied.

The excellent catalytic effect on methyl propiolate addition to a wide range of aromatic and aliphatic aldehydes promoted by inexpensive and commercially available BINOL-based ligand is reported. The catalyst systems showed high yields and excellent enantioselectivities for aromatic aldehydes, and excellent yields and high enantioselectivities for aliphatic aldehydes.

The new ion-exchange oxy-sulfide material has a three-dimensional open framework comprising the pseudo-T4 supertetrahedral [In4Sn16O10S34]12– cluster. This material has large pores and is a fast ion exchanger. It exhibits high selectivity in sequestering heavy metal ions from aqueous solutions including solutions containing heavy concentrations of sodium, calcium, ammonium, magnesium, zinc, carbonate, phosphate, and acetate ions. Moreover, the ion-exchange efficiency in competitive ion-exchange experiments involving mixtures of metal ions is significantly higher than for solutions of single metal ions.

A new type of alanine triazole (ATA) ligand was found to be an efficient partner for the stabilization of gold(III), thus rendering improved stability and high catalytic activities in allene synthesis and hydration reactions through the 3,3′-arrangement of propargyl esters and propargyl alcohols. In addition to Au(I), ATA-gold(III) was also proven to be an effective catalyst in promoting the formation of allenes with high yields. Furthermore, alanine triazole ruthenium has exhibited excellent potential as a means to catalyze borrowing hydrogen of alcohols and amines, ketones and alcohols.

The first organocatalytic hetero-Diels–Alder reaction of an in situ generated diene with either α-keto esters or β,γ-unsaturated α-keto esters was successfully developed. The densely functionalized dihydropyranones with a highly congested quaternary center were readily obtained in moderate to good yields with excellent enantioselectivities under mild conditions.

For the first time, a strategy for the enantioselective Rh-TaniaPhos catalyzed asymmetric hydrogenation of unprotected β-enamine phosphonates directly to free β-amino phosphonates is reported which occurs with high yields and good enantioselectivities (up to 86% ee).

Developing new catalytic technologies through C–H bond activation to synthesize versatile pharmaceuticals has attracted much attention in recent decades. This work introduces a new strategy in catalyst design for Pd(II)-catalyzed C–H bond activation in which non-redox metal ions serving as Lewis acids play significant roles. In the oxidative coupling of indoles with olefins using dioxygen, it was found that Pd(OAc)2 alone as the catalyst is very sluggish at ambient temperature which provided a low yield of the olefination product, whereas adding non-redox metal ions to Pd(OAc)2 substantially improves its catalytic efficiency. In particular, it provided bis(indolyl)methane derivatives as the dominant product, a category of pharmacological molecules which could not be synthesized by Pd(II)-catalyzed oxidative coupling previously. Detailed investigations revealed that the reaction proceeds by heterobimetallic Pd(II)/Sc(III)-catalyzed oxidative coupling of an indole with an olefin followed by Sc(III)-catalyzed addition with a second indole molecule. DFT calculations disclosed that the formation of heterobimetallic Pd(II)/Sc(III) species substantially decreases the C–H bond activation energy barrier, and shifts the rate determining step from C–H bond activation of indole to the olefination step. This non-redox metal ion promoted Pd(II)-catalyzed C–H bond activation may offer a new opportunity for catalyst design in organic synthesis, which has not been fully recognized yet.

We have described the first efficient one-pot method for the synthesis of acyloxy carbonyl compounds from ketones catalyzed by a Pybox–Cu(II) complex under mild conditions. A series of α-acyloxy ketone products were obtained in good to excellent yields.

A new transformation is presented that enables chemists to couple simple alkyl carboxylic acids with aryl zinc reagents under Ni-catalysis. The success of this reaction hinges on the unique use of redox-active esters that allow one to employ such derivatives as alkyl halides surrogates. The chemistry exhibits broad substrate scope and features a high degree of practicality. The simple procedure and extremely inexpensive nature of both the substrates and pre-catalyst (NiCl2·6H2O, ca. $9.5/mol) bode well for the immediate widespread adoption of this method.