Copper-Catalyzed Enantioselective Difluoromethylation-Alkynylation of Olefins by Solving the Dilemma between Acidities and Reduction Potentials of Difluoromethylating Agents.

Molecules containing a difluoromethyl group or a propargylic stereocenter are widely used in pharmaceuticals and agrochemicals, and 1,2-functionalization of olefins is an important method for introducing the two groups into molecules simultaneously. The construction of the propargylic stereocenter with terminal alkynes usually requires bases. However, difluoromethylating agents with high reduction potentials often decompose in the presence of bases because of their acidities, and those with low reduction potentials are stable but difficult to undergo the desired single electron transfer (SET) reduction. Using the linear relationship between reduction potential differences (ΔE) and Hammett substituent constants (σ) of difluoromethyl aryl sulfones, we solved the dilemma between acidities and reduction potentials of difluoromethylating agents. Herein, we report the first enantioselective difluoromethylation-alkynylation of olefins with difluoromethyl 4-chlorophenyl sulfone with high enantioselectivity (>90 % ee). We also extended this asymmetric fluoroalkylation-alkynylation reaction with other fluoroalkyl sulfones, which enabled efficient installation of trifluoromethyl, difluoroalkyl, difluorobenzyl, (benzenesulfonyl)-difluoromethyl and monofluoromethyl groups into products.

Chirality Sensing of N-Heterocycles via 19F NMR.

Methods to rapidly detect and differentiate chiral N-heterocyclic compounds become increasingly important owing to the widespread application of N-heterocycles in drug discovery and materials science. We herein report a 19F NMR-based chemosensing approach for the prompt enantioanalysis of various N-heterocycles, where the dynamic binding between the analytes and a chiral 19F-labeled palladium probe create characteristic 19F NMR signals assignable to each enantiomer. The open binding site of the probe allows the effective recognition of bulky analytes that are otherwise difficult to detect. The chirality center distal to the binding site is found sufficient for the probe to discriminate the stereoconfiguration of the analyte. The utility of the method in the screening of reaction conditions for the asymmetric synthesis of lansoprazole is demonstrated.

Optimization of production system of shale oil development in Ordos basin, China.

In this paper, production system (PS) of shale oil is optimized according to production data and indoor experiments, including core and fluid tests. Results showed that: ① Pressure drop rate at wellhead is a reasonable reference for the determination of post-fracture shut-in duration (PFSID). When pressure at a wellhead of horizontal well is relatively stable and the pressure drop less than 0.1 MPa per day for three consecutive days, PFSID ends; ② Flowback intensity of fracturing fluid affects the effectiveness of proppant underground, thus flowback intensity can be determined by the critical flow rate and safety factor of each proppant; ③ Flowback intensity should be varied during different development stages, which could be divided into four according to production gas and oil ratio(GOR) of a shale oil horizontal well: low, medium-high, high and high-low production GOR. During the stage of low production GOR, ratio of flow pressure and saturation pressure should be maintained greater than 1.0, and the initial daily liquid productivity for a hundred-meter oil-bearing lateral length in a horizontal well is 2.4 ~ 2.9 m3/d; and during the medium-high production GOR, high production GOR and high-low production GOR stages, the responding initial daily liquid productivity should be maintained between 0.8 ~ 1.0 or less than 0.8 respectively.

Enantioselective nickel-catalyzed dicarbofunctionalization of 3,3,3-trifluoropropene.

Despite paramount applications of chiral trifluoromethylated compounds in medicinal chemistry and materials science, limited strategies have been developed for catalytic asymmetric synthesis of such valuable fluorinated structures. Here, we report a nickel catalyzed enantioselective dicarbofunctionalization of inexpensive industrial chemical 3,3,3-trifluoropropene (TFP) with readily available tertiary alkyl and aryl iodides. The reaction overcomes the ß-F elimination side reaction of TFP, and proceeds efficiently under mild reaction conditions. The protocol possesses advantages, such as synthetic convenience, high enantioselectivity, and excellent functional group tolerance, providing rapid and straightforward access to chiral trifluoromethylated compounds of medicinal interest.

Fe-BPsalan Complex-Catalyzed Asymmetric [4 + 2] Cycloaddition of Cyclopentadiene with α,ß-Unsaturated Heterocycles.

An efficient iron-catalyzed asymmetric [4 + 2] cycloaddition of cyclopentadiene with α,ß-unsaturated acyl imidazoles or 2-cinnamoylisoindoline-1,3-dione derivatives was developed to afford the addition products in high yield and selectivity. Interestingly, the absolute structures of the addition products were controlled by the auxiliaries via different coordination modes with the same type of catalyst.

SulfoxFluor-enabled deoxyazidation of alcohols with NaN3.

Direct deoxyazidation of alcohols with NaN3 is a straightforward method for the synthesis of widely used alkyl azides in organic chemistry. However, known methods have some limitations such as high reaction temperatures and narrow substrate scope. Herein, a general and practical method for the preparation of alkyl azides from alcohols using NaN3 has been developed. N-tosyl-4-chlorobenzenesulfonimidoyl fluoride (SulfoxFluor) plays an important role in this deoxyazidation process, which converts a broad range of alcohols into alkyl azides at room temperature. The power of this deoxyazidation protocol has been demonstrated by successful late-stage deoxyazidation of natural products and pharmaceutically relevant molecules.

Regio- and enantioselective umpolung gem-difluoroallylation of hydrazones via palladium catalysis enabled by N-heterocyclic carbene ligand.

The enantioselective construction of C-CF2R (R: alkyl or fluoroalkyl) bonds has attracted the attention of synthetic chemists because of the importance of chiral fluorinated compounds in life and materials sciences. Catalytic asymmetric fluoroalkylation has mainly been realized under organocatalysis and Lewis acid catalysis, with substrates limited to carbonyl compounds. Few examples using transition-metal catalysis exist, owing to side reactions including decomposition and isomerization of fluoroalkylating reagents. Herein we report umpolung asymmetric difluoroallylation of hydrazones with 3-bromo-3,3-difluoropropene (BDFP) under palladium catalysis. Difluoroallylation products having quaternary chiral carbon centers are afforded in good yields with high α/γ- and enantioselectivities. The usefulness of the reaction products is demonstrated and an inner-sphere mechanism of the reaction is proposed. The use of chiral N-heterocyclic carbene as ligand is the key for the selectivities as well as the productivity of the reaction.

Cobalt-Catalyzed Asymmetric Cross-Coupling Reaction of Fluorinated Secondary Benzyl Bromides with Lithium Aryl Boronates/ZnBr2.

A cobalt-catalyzed asymmetric cross-coupling of α-bromo-α-fluorotoluene derivatives with a variety of aryl zincates derived from lithium aryl n-butyl pinacol boronates and ZnBr2 under mild reaction conditions was described. In addition to mild reaction conditions, another advantage includes the compatibility of various common functional groups such as fluoride, chloride, bromide, cyano, or ester groups. Furthermore, this protocol was successfully applied to the enantioselective synthesis of three fluorinated derivatives of biologically active compounds or drug molecules.

Facilitating the transmetalation step with aryl-zincates in nickel-catalyzed enantioselective arylation of secondary benzylic halides.

Nickel-catalyzed asymmetric cross-coupling of secondary alkyl electrophiles with different nucleophiles represents a powerful strategy for the construction of chiral tertiary carbon centers. Yet, the use of aryl Grignard reagents or aryl zinc halides in many reactions typically resulted in low enantioselectivity, mainly due to their slow transmetalation step in the catalytical cycle and consequently the requirement of relatively high temperature. Here we report that the use of lithium aryl zincate [Ph2ZnBr]Li facilitates the transmetalation step of the nickel-catalyzed cross-coupling reaction. Based on this discovery, a highly enantioselective construction of fluoroalkyl-substituted stereogenic center by a nickel-catalyzed asymmetric Suzuki-Miyaura coupling of α-bromobenzyl trifluoro-/difluoro-/mono- fluoromethanes with a variety of lithium aryl zincates [Ph2ZnBr]Li that  were in situ generated from the reaction of lithium organoboronate with 1.0 equivalent of ZnBr2 was described.

Inhibition of CTRP6 prevented survival and migration in hepatocellular carcinoma through inactivating the AKT signaling pathway.

C1qTNF-related proteins (CTRPs) are a member of the adiponectin paralogs family, which are implicated in regulation of various biological processes. Recently, CTRP6 was found upregulated in human hepatocellular carcinomas (HCC). However, the specific roles and molecular mechanisms of CTRP6 in HCC remain unclear. Here, we investigated the effects of CTRP6 on the vitality, apoptosis, migration, and invasion of HCC cells. Firstly, we measured the levels of CTRP6 in HCC tissues and cell lines. Our results showed that CTRP6 was markedly upregulated in HCC tissues and Hep3B cells. Then, the CTRP6 siRNA was transfected into Hep3B cells. Cell counting kit-8 (CCK-8) assay and flow cytometry analysis revealed that silencing CTRP6-induced cell viability inhibition, and apoptosis. The wound-healing and transwell assay showed that CTRP6 deficiency suppressed the migration and invasion of Hep3B cells. Meanwhile, the AKT phosphorylation level was reduced by CTRP6 silencing. Next, Hep3B cells were pretreated with insulin-like growth factor-1 (IGF-1) (an activator of AKT), and then transfected with CTRP6 siRNA, and the cell vitality, apoptosis, migration, and invasion were measured again. We found that all these alterations caused by CTRP6 inhibition could be reversed by IGF-1 treatment. Taken together, CTRP6 suppression blocked cell survival, migration, and invasion and promoted cell apoptosis through inactivating the AKT signaling pathway. Our findings present a novel potential molecular target for HCC therapy.

Enantioselective Trifluoromethylalkynylation of Alkenes via Copper-Catalyzed Radical Relay.

A novel enantioselective copper-catalyzed trifluoromethylalkynylation of styrenes, proceeding through a radical relay process, is described herein, which affords structurally diverse CF3-containing propargylic compounds in good yield with excellent enantioselectivities under very mild conditions. In addition, the reaction features wide substrate scope and good functional group tolerance. Moreover, the trifluoromethylalkynylated products can be easily converted into synthetically useful chiral terminal alkynes, allenes, Z-alkenes, as well as CF3-modified nonsteroidal anti-inflammatory drugs.

Asymmetric Synthesis of Silicon-Stereogenic Vinylhydrosilanes by Cobalt-Catalyzed Regio- and Enantioselective Alkyne Hydrosilylation with Dihydrosilanes.

The strategic carbon-to-silicon substitution at a stereogenic center can produce chiral silanes with significantly improved properties relative to their carbon congeners. We herein report an unprecedented cobalt-catalyzed asymmetric hydrosilylation of unsymmetric alkynes with dihydrosilanes that furnishes silicon-stereogenic vinylhydrosilanes with high regio- and enantioselectivity. The absolute configurations of the products were determined by chiroptical methods in combination with DFT calculations. The synthetic versatility of the vinylhydrosilanes as chiral building blocks was further demonstrated by asymmetric Si-H insertion and catalytic hydroboration reactions.

Copper-Catalyzed Highly Stereoselective Trifluoromethylation and Difluoroalkylation of Secondary Propargyl Sulfonates.

It is challenging to stereoselectively introduce a trifluoromethyl group (CF3 ) into organic molecules. To date, only limited strategies involving direct asymmetric trifluoromethylation have been reported. Herein, we describe a new strategy for direct asymmetric trifluoromethylation through the copper-catalyzed stereospecific trifluoromethylation of optically active secondary propargyl sulfonates. The reaction enables propargylic trifluoromethylation with high regioselectivity and stereoselectivity. The reaction could also be extended to stereospecific propargylic difluoroalkylation. Transformations of the resulting enantiomerically enriched fluoroalkylated alkynes led to a variety of chiral fluoroalkylated compounds, thus providing a useful protocol for applications in the synthesis of fluorinated complexes.

Enantioselective Construction of Trifluoromethoxylated Stereogenic Centers by a Nickel-Catalyzed Asymmetric Suzuki-Miyaura Coupling of Secondary Benzyl Bromides.

Trifluoromethoxy-substituted stereogenic centers can be constructed with high enantioselectivity by a nickel-catalyzed Suzuki-Miyaura coupling of readily available α-bromobenzyl trifluoromethyl ethers with a variety of aryl pinacol boronates. The coupling proceeds under mild reaction conditions, and a variety of common functional groups, such as fluoride, chloride, bromide, ester, enolizable ketone, nitro, cyano, amino, and vinyl moieties, were well tolerated. Furthermore, the reaction can be easily scaled up to gram quantities without a decrease in enantioselectivity.

Asymmetric Copper-Catalyzed Intermolecular Aminoarylation of Styrenes: Efficient Access to Optical 2,2-Diarylethylamines.

We have developed a copper-catalyzed enantioselective intermolecular aminoarylation of alkenes using a novel N-fluoro-N-alkylsulfonamide as the amine reagent, which could react with the Cu(I) catalyst to release a related amino radical. After addition to styrene, the generated benzylic radical could couple with a chiral L*CuIIAr complex to achieve enantioselective arylation. Various optical 2,2-diarylethylamines were efficiently synthesized from simple styrenes with high enantioselectivity, and these products can serve as valuable synthons toward bioactive molecules' synthesis.

Asymmetric Cu-Catalyzed Intermolecular Trifluoromethylarylation of Styrenes: Enantioselective Arylation of Benzylic Radicals.

A novel asymmetric radical trifluoromethyl-arylation of alkenes has been developed, which provides an efficient approach to access chiral CF3-containing 1,1-diarylmethane derivatives with good to excellent enantioselectivity. Various vinyl arenes and aryl boronic acids are compatible with these conditions. The utility of the method is demonstrated by accessing modified bioactive molecules.

Enantioselective Copper-Catalyzed Intermolecular Cyanotrifluoromethylation of Alkenes via Radical Process.

A novel enantioselective copper-catalyzed intermolecular cyanotrifluoromethylation of alkenes has been developed, in which a variety of CF3-containing alkylnitriles are furnished with excellent enantiomeric excess. Preliminary mechanistic studies revealed (1) the reaction was initiated by a SET process between activated Togni's CF3+ reagent and a Cu(I) catalyst; (2) the released CF3 radical readily added to styrene to provide a benzylic radical, which was then trapped by a chiral Cu(II) cyanide species to deliver the desired alkylnitriles; (3) a low concentration of the CN anion was crucial to obtain high enantioselectivity.

[Enantioseparation of ferroence derivatives with high performance liquid chromatography].

The method for the enantioseparation of ferroence derivatives, four derivatives with single chirality and three derivatives with double chiralities containing centre and face chirality, on chiral stationary phases, namely Chiralpak IC (cellulose-tris (3, 5-dichlorobenzene carbamate)) and Chiralpak IE3 (amylose-tris(3,5-dichlorobenzene carbamate)), was investigated. We found that the three derivatives of the four chiral ferroence derivatives with single chirality can be baseline separated on Chiralpak IE3; another one can be baseline separated on Chiralpak IC. Meanwhile, the three chiral ferroence derivatives with double chiralities can be baseline separated on Chiralpak IC. The research shows that the both kinds of chiral stationary phases exhibited high enantiomeric recognition capability to the enantiomers of the chiral ferroence derivatives. This two chiral stationary phases exhibited complementary selectivities in the enantioseparation of chiral ferroence derivatives. This study provides a reference method for the enantioseparation of chiral ferroence derivatives.

Enantioselective Bromo-oxycyclization of Silanol.

Relying on the nucleophilicity of silanol for building up silicon-incorporated scaffold with an enantiopure tetrasubstituted carbon center remains elusive. In this report, asymmetric bromo-oxycyclization of olefinic silanol by using chiral anionic phase-transfer catalyst is described. This protocol provided a facile entry to a wide arrangement of enantiopure benzoxasilole in moderate to excellent enantioselectivities depending on the unique reactivity of bromine/N-benzyl-DABCO complex.

Total Synthesis of (-)-Conolutinine.

The first enantioselective synthesis of (-)-conolutinine was achieved in 10 steps. The synthesis featured a catalytic asymmetric bromocyclization of tryptamine to forge the tricycle intermediate. Hydration of an alkene catalyzed by Co(acac)2 was also employed as a key step to diastereoselectively introduce the tertiary alcohol moiety. The absolute configuration of (-)-conolutinine was established to be (2S,5aS,8aS,13aR) based on this asymmetric total synthesis.