Thioallenoates in catalytic enantioselective [2+2]-cycloadditions with unactivated alkenes

The application of thioallenoates to catalytic enantioselective [2+2]-cycloadditions with unactivated alkenes is reported. In many cases, the thioallenoates examined exhibit superior reactivity and selectivity compared to the allenic esters generally used in these cycloadditions.     

Cobalt-catalyzed dimerization of alkenes

In the presence of CoX₂(PPh₃)₂/3 PPh₃ and zinc metal conjugated alkenes (CH₂CHCOOR, CH₂CHCN, CH₂CHSO₂Ph and CH₂CHCONEt₂) undergo reductive tail-to-tail dimerization to yield the corresponding saturated linear products. Under similar reaction conditions, vinylarenes (ArCHCH₂) give stereoselective head-to-tail dimerization products, trans-1,3-diarylbut-1-ene, in good to excellent yields.     

Cobalt-catalyzed efficient aziridination of alkenes

[reaction: see text]. Cobalt porphyrins are capable of catalyzing the aziridination of alkenes with bromamine-T as the nitrene source. Among cobalt complexes of different porphyrins, Co(TDClPP) is an effective catalyst that can aziridinate a wide variety of alkenes. The catalytic system can operate at room temperature in a one-pot fashion with alkenes as limiting reagents, forming the desired N-sulfonylated aziridine derivatives in high to excellent yields with NaBr as the byproduct.     

Studies on the effects of doping cesium metal(III) halides of the type Cs3MIII2X9 (MIII = Sb or Bi, X = Cl or Br)

A series of compounds, Cs₃M^III₂X₉ (M^III = Sb and Bi, X = Cl or Br) are doped with impurity ions (Ba²⁺, Ca²⁺, Sn²⁺, Pb²⁺, Mg²⁺, Fe²⁺, Tl³⁺, In³⁺, Se⁴⁺). Lattices doped with Sn(II), Pb(II) and Se(IV) are colored. Sn-119m Mössbauer data are consistent with the donation of Sn-5s electron density from tin(II) to a conduction band to give a pseudo-tin(IV) electronic environment.     

Copper-catalyzed oxytrifluoromethylation of unactivated alkenes

A mild, versatile, and convenient method for the efficient oxytrifluoromethylation of unactivated alkenes based on a copper-catalyzed oxidative difunctionalization strategy has been developed. This methodology provides access to a variety of classes of synthetically useful CF(3)-containing building blocks from simple starting materials.     

Organocatalytic hydroacylation of unactivated alkenes

N-Heterocyclic carbenes interact with aldehydes to generate the Breslow intermediate, a rendering of the prototypical electrophile into a nucleophile (umpolung). Recent work has indicated that these intermediates may also add to simple, unpolarized alkenes. The use of a chiral precatalyst leads to the generation of the derived adducts with high yields and very high selectivities.     

Radical aminomethylation of unactivated alkenes

S-Succinimidomethyl- and S-phthalimidomethyl xanthates are added efficiently to various alkenes resulting in an overall aminomethylation process. In contrast, under similar conditions, S-pyrrolidonyl xanthate gives rise mostly to oligomers. This unexpected difference in reactivity is attributed to the more important allylic character of the intermediate radical in the case of the imide derivative as compared to the lactam.     

Synthesis,structure and magnetic properties of the dinuclear complex [1,3-C6H4{NC(Ph)N(SiMe3)}2]3Dy2 coordinated by ansa-bis(amidinate) ligands with a m-phenylene linker

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Synthesis of 4H-1,3-benzoxazin-4-ones from 2,2-diazidobenzofuran-3(2H)-ones

Benzoxazine derivatives are useful building blocks and display various biological activities. We serendipitously discovered and subsequently developed a new one pot method for the synthesis of 2-(dimethyl amino)/2-morpholino/2- (piperidin-1-yl)-4H-benzo[e][1,3]oxazin-4-ones from corresponding substituted 2,2-diazidobenzofuran 3(2H) - ones and N-formyl dimethyl amine (DMF)/N-formylmorpholine/N-formylpiperidine using m-CPBA at 100?°C in moderate to good yields. We also demonstrated the utility of 4H-benzoxazines for the synthesis of other medicinally important compounds such as 2-hydroxyphenyl substituted 1,2,4-triazoles, unsymmetrical 1,3,5-triazines, and 1,2,4-oxadiazoles.     

Leaving group effect on photochemistry of ortho-alkylphenacyl carboxylate

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Regioselective functionalization of gem-bis(trifluoromethylated) alkanols

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Pd/Cu-Catalyzed amide-enabled selectivity-reversed borocarbonylation of unactivated alkenes

The addition reaction between CuBpin and alkenes to give a terminal boron substituted intermediate is usually fast and facile. In this communication, a selectivity-reversed procedure has been designed and established. This selectivity-reversed borocarbonylation reaction is enabled by a cooperative action between palladium and copper catalysts and proceeds with complete regioselectivity. The key to the success of this transformation is the coordination of the amide group and slower CuBpin formation by using KHCO₃ as the base. A wide range of β-boryl ketones were produced from terminal unactivated aliphatic alkenes and aryl iodides. Further synthetic transformations of the obtained β-boryl ketones have been developed as well.

A selectivity-reversed borocarbonylation reaction has been developed with complete regioselectivity.

The catalytic borocarbonylation of alkenes represents a novel synthetic tool for the simultaneous installation of boron and carbonyl groups across alkenes, enabling rapid construction of molecules with high complexity from abundant alkenes. In particular, the obtained organoboron compounds are versatile synthetic intermediates that can be readily converted into a wide range of functional groups with complete stereospecificity.¹ Consequently, several catalytic systems have been developed to diversify the molecular frameworks through carbonylative borofunctionalization.² In general, carbonylative borofunctionalization of alkenes proceeds via an alkyl-copper intermediate, which was produced by the addition of CuBpin to the terminal position of the alkene starting material,³ followed by CO insertion and other related steps. A new C–B bond is formed at the terminal position of the alkene and a carbonyl group has been installed at the β-position simultaneously (Scheme 1a). However, in contrast to the progress in the borocarbonylation, a selectivity-reversed procedure (the boryl group is installed at the internal position) to give β-boryl ketone products is still unprecedented.Open in a separate windowScheme 1Strategies for borocarbonylation of activated alkenes.Recently, several attractive strategies have emerged for the borofunctionalization of unactivated alkenes to give β-boryl products.^4–7 In 2015, Fu, Xiao and their co-workers established a copper-catalyzed regiodivergent alkylboration of alkenes.^4a In the same year, Miura and Hirano''s group reported a copper-catalyzed aminoboration of terminal alkenes.^4b In these two attractive procedures, the regioselectivity was controlled by the ligand applied. More recently, an intermolecular 1,2-alkylborylation of alkenes was described by Ito''s research group.⁵ A radical-relay strategy was used to achieve the targeted regioselective addition. Furthermore, Engle and co-workers explored a palladium-catalyzed 1,2-carboboration and -silylation reaction of alkenes.⁶ Stereocontrol can be achieved in this new procedure with the assistance of a chiral auxiliary which is a coordinating group in this case.Inspired by these pioneering studies, we assumed that if the reaction could be initiated by the insertion of an acylpalladium complex into alkenes, followed by transmetalation with CuBpin before reductive elimination, β-boryl ketones can finally be produced (Scheme 1b). However, due to the inherent reactivity of the palladium species toward alkenes, olefin substrates were usually restricted to styrenes and a large excess of them is typically required (>6 equivalents).^8,9 Therefore, the critical part of the reaction design is to promote the reaction of the acylpalladium intermediate with alkenes faster than the insertion of CuBpin into olefins. One of the ideas is taking advantage of the coordinating group to transform the reaction from intermolecular to intramolecular. Among the developed directing groups,¹⁰ 8-aminoquinoline (AQ) is interesting and has been relatively well studied by various groups in a number of novel transformations.^11–13 Although the AQ directing group contains a NH group which can participate in intramolecular C–N bond formation,¹⁴ we believe that the selectivity-reversed borocarbonylation of alkenes can potentially be achieved through cooperative Pd/Cu catalysis. Then, valuable β-boryl ketones can be produced from readily available substrates directly and effectively.To test the viability of our design on selectivity-reversed borocarbonylation of alkenes, N-(quinolin-8-yl)pent-4-enamide (1a), iodobenzene (2a), and bis(pinacolato)diboron (B₂pin₂) were chosen as model substrates for systematic studies. As shown in 15 In the testing of palladium precursors, allylpalladium chloride dimer proved to be the best palladium catalyst for this reaction, affording 3a in 41% yield (†) and tend to generate the by-product β-aminoketone. Xantphos was found to be superior to the other tested bidentate ligands (

Self-condensation of N-substituted (4H-thieno[3,2-b]-pyrrol-5-yl)methanols into bis(thienopyrrolyl)methanes

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Efficient water-soluble catalytic system RhI-CAP for biphasic hydroformylation of olefins

Rhodium-catalysed hydroformylation of styrene and aliphatic olefins under biphasic conditions in the presence of watersoluble 1,4,7-triaza-9-phosphatricyclo[5.3.2.1^4,9]tridecane (CAP) chemoselectively affords aldehydes. Multiple catalyst reuse without loss in performance is demonstrated.     

15th Chinese International Peptide Symposium

正As one of the most important and influential peptide conferences in the world,Chinese International Peptide Symposium(CPS)was founded in 1990 and has been held every two years for14 consecutive sessions.From July 4~(th)to 6~(th),2018,the 15th CPS will be held in Shenzhen and hosted by Tsinghua University.This conference will focus on the topics of"Peptide:Technological Innovation and a Better Life",covering the synthesis,structure and function of peptides and proteins,peptide-based drug discovery,     

Enantiomerically pure piperazines via NaBH4/I2 reduction of cyclic amides

Enantiomerically pure (3S,7R,8aS)-3-phenyloctahydropyrrolo[1,2-a]pyrazine-7-ol, (3S,7R,8aS)-3-methyl octahydropyrrolo[1,2-a]pyrazine-7-ol, (3S,7R,8aS)-3-isopropyloctahydropyrrolo[1,2-a]pyrazine-7-ol and (3S,7R,8aS)-3-isobutyloctahydropyrrolo[1,2-a]pyrazine-7-ol 16d were synthesized via preparation of the corresponding cyclic amides from enantiomerically pure l-proline and hydroxyproline derivatives followed by reduction using sodium borohydride-iodine.     

Direct hydrogenation of CO2 on deposited iron-containing catalysts under supercritical conditions

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Synthesis of polyhydroxylated bicyclic tetrahydrofurans and tetrahydropyrans via a stereoselective domino cyclization/reduction reaction

A novel reaction cascade involving a Lewis acid-induced migration of an isopropylidene protecting group followed by the formation of a pyranose or furanose ring and subsequent reduction of the hemiacetal is described. Depending on the reaction conditions, as well as, the stereochemistry of the substrate, polyhydroxylated tetrahydrofurans or tetrahydropyrans can be obtained in reasonable yields. The synthons used in this transformation were prepared via a highly stereoselective one-pot tandem reaction, consisting of a 1,4-Michael addition of vinylmagnesium bromide to d-glucose-derived cyclohexenone followed by aldol reaction with 2,3-O-isopropylidene-d-glyceraldehyde.