PC-Phos Enabled Catalytic Palladium-heteroallyl Asymmetric Cycloaddition.

Asymmetric cycloaddition reactions are the most powerful tool to the expeditious construction of enantioenriched cyclic motifs in organic chemistry. In sharp contrast to well-developed cycloaddition reactions via the palladium-trimethylenemethane (Pd-TMM) intermediate, hetero (3 + 2) cycloadditions of the heteroallyl cations remain rare, largely due to their thermally forbidden nature. To the best of our knowledge, there is no example of asymmetric version leading to enantioenriched heterocycles reported so far. Herein we enabled the first example of catalytic asymmetric (3 + 2) cycloaddition of electrophilic palladium-heteroallyl zwitterion intermediate (Pd-OTMM or Pd-NTMM) with cyclic or acyclic 1,3-dienes via a pathway terminated with C-N or C-O bond formation, delivering the highly substituted or fused pyrrolidine and tetrahydrofuran rings in high yields with excellent regio-, diastereo-, and enantioselectivity. Engineering the PC-Phos, one of the chiral sulfinamide phosphine (Sadphos) type ligands, by introducing the di-tert-butyl or/and 3,5-difluorophenyl group is a vital component in achieving excellent catalytic reactivity and enantioselectivity.

The complete chloroplast genome sequence of Clivia robusta.

In this study, we reported the complete chloroplast genome sequence of Clivia robusta for the first time. The complete chloroplast genome of C. robusta was 157,130 bp in length, containing a large single-copy region (LSC, 85,430 bp), a small single-copy region (SSC, 18,278 bp), and two inverted repeat regions (IRs, 26,711 bp). The overall GC content was 38.01%. The chloroplast genome contained 128 genes in total, including 86 protein-coding, 34 tRNA, and eight rRNA genes. The phylogenetic tree showed that C. robusta formed a monophyletic clade with other Clivia species.

The complete chloroplast genome sequence of Clivia miniata var. citrina.

The complete chloroplast genome of Clivia miniata var. citrina was assembled and subjected to phylogenetic analysis in this study. The complete chloroplast genome of C. miniata var. citrina was 158,112 bp in length, containing a large single-copy region (LSC, 86,202 bp), a small single-copy region (SSC, 18,334 bp), and two inverted repeat regions (IRs, 26,788 bp). The GC content was 37.97%. A total of 130 genes were annotated, including 86 protein-coding genes, 36 tRNA and 8 rRNA genes. Phylogenetic analysis showed that C. miniata var. citrina was the most related with C. miniata and they formed a monophyletic group that was sister to the clade of Hippeastrum, Leucojum, Narcissus and Lysoris.

Pd/GF-Phos-Catalyzed Asymmetric Three-Component Coupling Reaction to Access Chiral Diarylmethyl Alkynes.

Significant attention has been given in the past few years to the selective transformations of N-tosylhydrazones to various useful compounds. However, the development of enantioselective versions poses considerable challenges. Herein we report a Pd-catalyzed enantioselective three-component coupling of N-tosylhydrazone, aryl halide, and terminal alkyne under mild conditions utilizing a novel chiral sulfinamide phosphine ligand (GF-Phos), which provides a facile access to chiral diarylmethyl alkynes, which are useful synthons in organic synthesis as well as exist as the skeleton in many bioactive molecules. A pair of enantiomers of the product could be easily prepared using the same chiral ligand by simply changing the aryl substituents of the N-tosylhydrazone and aryl halide. The salient features of this reaction include the readily available starting materials, general substrate scope, high enantioselectivity, ease of scale-up, mild reaction conditions, and versatile transformations.

The complete chloroplast genome sequence of Clivia caulescens.

Clivia caulescens is an evergreen herbaceous flower with high ornamental value. In this study, we report its complete chloroplast genome sequence. The whole chloroplast genome was 158,149 bp in length, with a large single copy region (LSC, 86,250 bp), a small single copy region (SSC, 18,343 bp), and two inverted repeat regions (IRs, 26,778 bp). The overall GC content was 37.91%. There were 128 genes annotated, including 86 protein-coding genes, 34 tRNA genes, and eight rRNA genes. The phylogenetic tree showed that C. caulescens formed a monophyletic clade with C. miniata, C. miniata var. aurea, and C. gardenii.

Palladium-Catalyzed Asymmetric Tandem Denitrogenative Heck/Tsuji-Trost of Benzotriazoles with 1,3-Dienes.

The asymmetric denitrogenative cycloaddition has emerged as a powerful tool to build chiral aza-heterocyles. However, only one example of asymmetric denitrogenative cycloaddition of benzotriazole with unsaturated hydrocarbons has been explored so far, because the ring-opening of benzotriazole to generate α-imino metal carbenoid species is a thermodynamically unfavorable process. We herein report an efficient asymmetric denitrogenative cycloaddition of benzotriazoles with cyclic and acyclic 1,3-dienes enabled by Pd and chiral sulfonamide phosphine ligand. A variety of substituted hexahydrocarbazoles and indolines were delivered in good yields with high ee values. Interestingly, a pair of enantiomers could be obtained with the use of Xu1 and PC2 with the same absolute configuration. The synthetic utilities of the optically active hexahydrocarbazoles were also showcased.

Simultaneous construction of axial and planar chirality by gold/TY-Phos-catalyzed asymmetric hydroarylation.

The simultaneous construction of two different chiralities via a simple operation poses considerable challenge. Herein a cationic gold-catalyzed asymmetric hydroarylation of ortho-alkynylaryl ferrocenes derivatives is developed, which enable the simultaneous construction of axial and planar chirality. The here identified TY-Phos derived gold complex is responsible for the high yield, good diastereoselectivity (>20:1 dr), high enantioselectivities (up to 99% ee) and mild conditions. The catalyst system also shows potential application in the synthesis of chiral biaryl compounds. The cause of high enantioselectivity of this hydroarylation is investigated with density functional theory caculation.

Palladium/TY-Phos-Catalyzed Asymmetric Intermolecular α-Arylation of Aldehydes with Aryl Bromides.

Despite much progress has been made in the asymmetric α-arylation reactions of cyclic ketones, lactones and lactams, the enantioselective α-arylation of acyclic carbonyl compounds lagged much behind due to the in situ generated Z/E-enolate intermediates leading to opposite enantiomers. Especially, the asymmetric α-arylation of acyclic aldehydes is a long-standing challenge, because of the highest activity among carbonyl compounds leading to various competitive side reactions. Herein we reported an efficient Pd-catalyzed asymmetric intermolecular α-arylation reaction of α-alkyl-α-aryl disubstituted aldehydes with aryl bromides, which provides a rapid access to chiral aldehydes bearing an α-all-carbon quaternary stereocenter in moderate to good yields with good er in most cases. In addition, a pair of enantiomers could be easily prepared with the use of the same ligand by exchanging the aryl groups of aldehyde and aryl bromide.

Au-Catalyzed Formal Allylation of Diazo(thio)oxindoles: Application to Tandem Asymmetric Synthesis of Quaternary Stereocenters.

We report an efficient Au(I)-catalyzed formal allylation of diazo(thio)oxindoles using allyltrimethylsilane to give 3-allyl (thio)oxindoles, which are difficult to access by using traditional alkylation methods under basic conditions. The approach enables a highly stereoselective synthesis of quaternary (thio)oxindoles via a formal allylation-asymmetric Michael addition sequence. These adducts are versatile synthons for spirocyclic (thio)oxindoles. Initial biological studies reveal that chiral thiooxindoles show promising antiproliferation activity that is better than that of the corresponding oxindoles.

Copper-catalyzed cyclization reaction: synthesis of trifluoromethylated indolinyl ketones.

A novel, simple, effective and rapid synthetic method to construct the C-2 trifluoromethylated indolinyl ketones via a copper-catalyzed cyclization reaction between N-alkylaniline and ß-(trifluoromethyl)-α,ß-unsaturated enones was developed. The results of the control experiments show that the reaction may involve a radical mechanism by a single-electron transfer process. Moreover, a broad substrate scope and good functional groups, high diastereoselectivities (dr, up to >20 : 1) as well as gram-scale synthesis make this approach highly attractive.

Direct Electrochemical Defluorinative Carboxylation of gem-Difluoroalkenes with Carbon Dioxide.

We report a facile and economical synthesis of α-fluoroacrylic acids via direct electrochemical defluorinative carboxylation of gem-difluoroalkenes with CO2. By using a platinum plate as the working cathode and a cheap nickel plate as the anode in a user-friendly undivided cell under constant current conditions, the reactions proceed smoothly under room temperature, without the use of expensive transition metal catalysts, ligands, external base or reductant, affording the desired adducts in up to 83% yield and 20:1 Z/E ratio, with good functional group tolerance. A cyclic voltammetry study was conducted and suggested a novel ECEC process.

Design and Synthesis of TY-Phos and Application in Palladium-Catalyzed Enantioselective Fluoroarylation of gem-Difluoroalkenes.

The first example of highly enantioselective fluoroarylation of gem-difluoroalkenes with aryl halides is presented by using a new chiral sulfinamide phosphine (Sadphos) type ligand TY-Phos. N-Me-TY-Phos can be easily synthesized on a gram scale from readily available starting materials in three steps. Salient features of this work including readily available starting materials, good yields, high enantioselectivities as well as broad substrate scope make this approach very practical and attractive. Notably, the asymmetric synthesis of an analogue of a biologically active molecule is also reported.

Alcohol amine-catalyzed CO2 conversion for the synthesis of quinazoline-2,4-(1H,3H)-dione in water.

The conversion of CO2 to high value-added chemicals in water using environment-friendly and cost-effective catalysts is a very significant topic. In this work, a green method for the conversion of CO2 catalyzed by alcohol amines has been developed. Alcohol amines showed considerable activating ability to CO2 in the cyclization with 2-aminobenzonitrile to quinazoline-2,4(1H,3H)-dione in water. Notably, when diethanolamine (DEA) was used as the catalyst, 94% yield of quinazoline-2,4-(1H,3H)-dione could be achieved. A plausible mechanism has been proposed based on the 1H NMR, FT-IR analysis and DFT calculation. The excellent catalytic performance is attributed to the combined effect of both the secondary amine and hydroxyl groups on alcohol amines with the assistance of water in the formation of carbamate. Water plays a bi-functional role of solvent and co-catalyst in this catalytic process. Catalysts can be easily recovered and reused five times without significant loss of activity.

Multifunctional 1,3-diphenylguanidine for the carboxylative cyclization of homopropargyl amines with CO2 under ambient temperature and pressure.

Herein, we report that 1,3-diphenylguanidine (DPG) could be utilized for the carboxylative cyclization of homopropargyl amines with CO2 under ambient temperature and pressure, in combination with AgSbF6, which enabled the synthesis of both chiral and achiral 2-oxazinones efficiently. A mechanistic study revealed that the multi-functionality of DPG is critical to the success of the reaction.

Chiral bifunctional bisphosphine enabled enantioselective tandem Michael addition of tryptamine-derived oxindoles to ynones.

A chiral phosphine-catalyzed tandem Michael addition of tryptamine-derived oxindoles to ynones has been developed, which provides facile access to a series of optically enriched spiro[pyrrolidine-3,3'-oxindole] compounds in good yields with good to excellent enantio- (up to 97% ee) and diastereoselectivities (up to 20 : 1 dr). Mechanistic studies indicate that this tandem reaction proceeds via an intermolecular aza-Michael/intramolecular Michael addition process.

A neutral Cu-based MOF for effective quercetin extraction and conversion from natural onion juice.

We report herein a new microporous neutral three-dimensional (3D) metal-organic framework [Cu2(L)(DMF)(H2O)]·guest (1·guest) composed of copper paddle-wheel and flexible tetracarboxylic acid linkers (DMF = N,N-dimethylformamide, H4L = tetrakis[(6-carboxynaphthoxy)methyl]methane). Surprisingly, this MOF with neutral cavities can not only extract pure quercetin (QT) but also convert it into Cu-QT during the desorption process. It has been well characterized by UV-vis, IR, ESI-MS and TEM-EDS studies. Moreover, it can efficiently extract natural product QT from fresh QT-rich onion juice and rapidly convert it into Cu-QT with a relatively high conversion rate.

The complete chloroplast genome sequence of the threatened Cypripedium calceolus (Orchidaceae).

The complete chloroplast genome of Cypripedium calceolus, a rare species in the family Orchidaceae was reported in this study. The genome size is 175,122 bp in length, and contains four sub-regions: 97,486 bp of large single copy (LSC) and 22,260 bp of small copy (SSC) regions, separated by 27,688 bp of inverted repeat (IR) regions. A total of 133 genes were annotated, including 87 protein-coding genes, 38 tRNA genes and 8 rRNA genes. The GC content of this cp genome is 34.36%. Phylogenetic analysis revealed a close relationship between C. calceolus with C. japonicum and C. formosanum. This is the first complete cp genome for C. calceolus that would be useful for conservation and phylogenetic studies of this species.

Chirality Transfer in Rhodium(I)-Catalyzed [3 + 2]-Cycloaddition of Vinyl Aziridines and Oxime Ethers: Atom-Economical Synthesis of Chiral Imidazolidines.

A highly efficient and stereoselective synthesis of enantioenriched imidazolidines by rhodium-catalyzed intermolecular [3 + 2] cycloaddition reaction of chiral vinyl aziridines and oxime ethers has been successfully developed. Notably, both aldoximes and ketoximes are suitable substrates to afford the corresponding chiral imidazolidines in high yields with good stereoselectivity. This transformation represents an unprecedented example that utilizes ketimine derivatives as an aza-[2C]-component in cycloadditions of vinyl aziridines.

Divergent Access to Functionalized Pyrrolidines and Pyrrolines via Iridium-Catalyzed Domino-Ring-Opening Cyclization of Vinyl Aziridines with ß-Ketocarbonyls.

A useful synthesis of five-membered N-heterocycles has been developed through an iridium-catalyzed domino-ring-opening cyclization of vinylaziridines with ß-ketocarbonyls. α-Substituted 1,3-dicarbonyls reacted with vinylaziridines to give 2-methylenepyrrolidines bearing two adjacent sp3-carbon centers with moderate to excellent diastereoselectivity, while the reaction of α-unsubstituted 1,3-dicarbonyls afforded 2-pyrrolines in good yield.

Enantioselective Phosphine-Catalyzed Allylic Alkylations of mix-Indene with MBH Carbonates.

The first enantioenriched synthesis of 1,1,3-trisubstituted (trifluoromethyl)indene derivatives, bearing a quaternary stereogenic carbon center, is reported using a simple chiral sulfinamide phosphine-catalyzed asymmetric allylic alkylation of a mixture of indenes with Morita-Baylis-Hillman carbonates. The resulting derivatives can serve as a valuable synthetic building block for some drugs and natural products. Broad substrate scope and high regio- and enantioselectivity of this reaction were particularly remarkable.