The applications of Schiff bases in Ti-catalyzed asymmetric alkynylation of aldehydes

Sciff bases 1 and 2, .which were derived from chiral aminoalcohols, were used as figands in Ti-catalyzed asymmetric alkynylation of aldehydes. Good enantioselectivities （up to 88% ee） and high chemical yields （80-90%） were obtained.

Visible-light-induced decarboxylative alkynylation of carboxylic acids in batch and continuous flow

A green efficient photoredox-catalyzed decarboxylative alkynylation of carboxylic acids with alkynyl bromides has been developed.This broadly applicable protocol is presented whereinα-amino,aliphatic andα-oxy acids are converted into useful alkynylation products.The commercially-available organic photocatalyst 4CzIPN is used as the photocatalyst,organic base DBU is utilized as the base,and DMSO serves as solvent.This strategy features mild conditions,is metal-free,and is environmentally friendly.The batch and continuous-flow protocols described were applied to obtain a broader substrate scope of functionalization(more than 50 examples).Furthermore,we demonstrate that the use of microflow technology enhanced and intensified the reaction process,achieving significantly reduced reaction times(i.e.,10 min of residence time).

Pd-catalyzed asymmetric carbonyl alkynylation:Synthesis of axial chiral ynones

Ynones are important skeletons in bioactive molecules and valuable building blocks for organic synthesis,thus great efforts have been devoted to their preparation.While,introducing prochiral substrates to construct ynones bearing a chiral framework is unrealized to date.Herein,we reported the first example of Pd/SOP-catalyzed asymmetric carbonylative alkynylation via a non-classical carbonylative Sonogashiratype approach(acyl-Pd(Ⅱ)species generated from nucleophiles).By using cyclic diaryliodonium salts as prochiral substrates,various axial chiral ynones with good functional group tolerance(39 examples),satisfied yields(71%-96%)and excellent enantioselectivities(generally 94%-99%ee)were produced.Synthesis of bioactive compounds,scale-up experiment and useful transformations were also conducted to demonstrate the utility of this process.

Palladium-Catalyzed Oxidative Alkynylation of Allenyl Ketones: Access to 3-Alkynyl Poly-substituted Furans

Furans bearing alkynyl substituents are highly useful in organic synthesis.However,the methodologies to access these important furan derivatives are rather limited.We herein report an efficient synthesis of alkynylated furan derivatives based on Pd-catalyzed oxidative cross-coupling reaction between allenyl ketones and terminal alkynes.This novel synthesis of alkynylated furans with wide substrate scope is operationally simple and tolerates various functional groups.Mechanistically,the formation of the palladium carbene through cycloisomerization and the subsequent alkynyl migratory insertion are proposed as the key steps in the transformation.The reaction reported in this paper further demonstrates the generality of the carbene-based cross coupling.

Recent Developments in Copper(Ⅰ)-Catalyzed Enantioselective Alkynylation Reactions via a Radical Process

Alkynes are one of the most significant functional groups in organic chemistry and great efforts have been made to explore efficient approach for the construction of chiral alkynes.The asymmetric C(sp^(3))–C(sp)cross-coupling provides a significant complementary strategy through radical-initiated process.However,the stereocontrol of highly reactive and unstable radical intermediate has been a challenge for decades.To address this problem,a variety of chiral ligands are developed for initiating the reaction and achieving enantiocontrol of alkyl radicals.This review summarizes recent developments in copper-catalyzed enantioselective alkynylation of prochiral alkyl radicals and their brief mechanistic studies.

Copper catalyzed/mediated direct B–H alkenylation/alkynylation in carboranes

Base metal catalyzed regioselective cage B–H functionalization has been achieved. Under the assistance of a bidentate directing group, Cu-catalyzed [4+2] annulation of carboranyl amides with internal alkynes affords unprecedented C,B-substituted carborane-fused-pyridone derivatives, whereas the use of terminal alkynes leads to B–H/C(sp)–H dehydrocoupling products. The isolation and structural identification of a notably stable Cu(Ⅰ) intermediate shed light on the reaction mechanism, which is proposed to involve a Cu(Ⅲ) intermediate.

Highly Stereoselective C-Glycosylation by Photocatalytic Decarboxylative Alkynylation on Anomeric Position:A Facile Access to Alkynyl C-Glycosides

The highly stereoselective synthesis of diverse medicinally valuable alkynyl C-glycosides under mild and green reaction conditions remains a great challenge.Herein,we wish to report a visible-light induced photocatalytic decarboxylative alkynylation approach.By utilizing an iridium photocatalyst in the presence of visible light,glycosyl radicals are in-situ generated via the decarboxylation of anomeric acids and efficiently coupled with a variety of ethynylbenziodoxolones(EBXs),which allows the facile synthesis of a variety of alkynyl C-glycosides in moderate to high yields and with excellent diastereoselectivity.

Oxidative C—H alkynylation of 3,6-dihydro-2H-pyrans

Current synthesis of α-substituted 3,6-dihydro-2H-pyrans dominantly relies on functional group transformation. Herein, a direct and practical oxidative C -H alkynylation and alkenylation of 3,6-dihydro-2H-pyran skeletons with a range of potassium trifluoroborates is developed. The metal-free process is well tolerated with a wide variety of 3,6-dihydro-2H-pyrans, rapidly providing a library of 2,4-disubstituted 3,6-dihydro-2H-pyrans with diverse patterns of α-functionalities for further diversification and bioactive small molecule identification.

Asymmetric Alkynylation of Tertiary Carbon-Centered Radical via Copper-Catalyzed Radical Relay

Alkynes are frequently found in a high proportion of natural products and bioactive moleculars,as well as a common synthon in organic synthesis,which can be easily transformed to an alkenyl,alkyl,heteroaryl,or carboxylic acid group.The enantioselective construction of alkyne substituted all carbon quaternary stereocenters is rarely reported and still a big challenge.As part of our continuous effort on developing asymmetric radical transformations,we found introducing an amidyl group(CONHAr)adjacent to the tertiary carbon radical could enable the asymmetric radical coupling with alkyne reagents.The amidyl group may stabilize the tertiary carbon radical or coordination with the chiral copper catalyst.Herein,we communicate a copper-catalyzed asymmetric trifluoromethyl-alkynylation ofα-aryl substituted acrylamides,which provides a straightforward and efficient access to chiral quaternary all-carbon centers bearing alkynyl groups in good yields and enantioselectivities.This reaction was also applied for the synthesis of chiral functionalized dipeptide.

Catalytic C-N Bond Alkynylation of N-Benzylic Sulfonamides with Terminal Alkynes

A new cross-coupling reaction of N-benzylic sulfonamides with terminal alkynes for the synthesis of internal alkynes is reported.In the presence of 5 mol%of(Tf)_(2)NH/Bi(OTf)_(3)(1∶1),a broad range of N-benzylic sulfona-mides react smoothly with arylacetylenes to afford structurally diverse internal alkynes in moderate to excellent yields.We reasoned that vinyl cations could be formed by the regioselective attack of terminal alkynes with benzyl cations generated in situ from N-benzylic sulfonamides under acidic conditions,which then eliminated to form a carbon-carbon triple bond.

NiH-catalyzed asymmetric hydroalkynylation of α,β-unsaturated amides

An enantioselective NiH-catalyzed hydroalkynylation ofα,β-unsaturated amides is reported.A wide range ofα,β-unsaturated amides and bromoalkynes are suitable substrates for this reaction,which proceeds under mild conditions,allowing access to a variety of enantioenriched chiralβ-alkynyl amides.β,γ-Unsaturated amides can also be used as substrates and undergo theβ-selective hydroalkynylation with a slightly lower enantiomeric excess.

Mechanochemical synthesis of oxygenated alkynyl carbon materials with excellent Hg(Ⅱ) adsorption performance from CaC2 and carbonates

Adsorptive removal of heavy metal ions from wastewater is very important,and the key is the development of efficient sorbents.In this work,oxygenated alkynyl carbon materials(OACMs)were synthesized via mechanochemical reaction of CaC_(2) and a carbonate(CaCO_(3),Na2CO_(3),or NaHCO_(3))at ambient temperature.The resultant OACMs are micro mesoporous carbon nanomaterials with high specific area(>648 m2 g^(-1)),highly crosslinked texture,and rich alkynyl and oxygenated groups.The OACMs exhibit excellent Hg(Ⅱ)adsorption due to the soft acid-soft base interaction between alkynyl and Hg(Ⅱ),and OACM-3 derived from CaC_(2) and NaHCO_(3) has the saturated Hg(Ⅱ)adsorbance of 483.9 mg g^(-1)along with good selectivity and recyclability.The adsorption is mainly chemisorption following the Langmuir mode.OACM-3 also shows high adsorbance for other heavy metal ions,e.g.256.6 mg g^(-1)for Pb(II),232.4 mg g^(-1)for Zn(II),and 198.7 mg g^(-1)for Cu(II).This work expands the mechnochemical reaction of CaC_(2)with carbonates and possibly other oxyanionic salts,provides a new synthesis approach for functional alkynyl carbon materials with excellent adsorption performance for heavy metal ions,as well as a feasible approach for CO2 resource utilization.

A new synthesis of alkynyl tellurides promoted by CsOH and 4 MS

The mixture of cesium hydroxide and terminal alkynes in dry DMF in the presence of 4 A molecular sieves was stirred for 3.0 h at room temperature under N2, then aryltellurenyl bromide in THF was added, and the reaction mixture was stirred for 2.0 h. Alkynyl tellurides were obtained in about 90% yields by flash chromatography.

Triphenylphosphine-catalyzed isomerization of alkynyl ketones in aqueous solution

An efficient isomerization of alkynyl ketones to (E,E)-diene ketones was developed. The reaction catalyzed by 20 mol% triphenylphosphine in aqueous media gave the desired products in good yields.

High extraction ability of 1,3-dialkynyl calixarene towards mercury(Ⅱ) ion

The reaction of 1,3-dipropyn-2-yloxycalix[4]arene with mercury（U） acetate could give mercury-containing alkynyl calixarene polymer. The extraction behavior of 1,3-dipropyn-2-yl-oxycalix[4]arene towards mercury（Ⅱ） ion was examined. When the mole ratio of Hg^2＋/calixarene was 1：1, the extractive percent can reach to 99.1%, and the extraction capacity was up to 431 mg/g. It could also decrease the Hg^2＋ concentration from 5 to 0.85 mg/L, which was only 17% of the national standard of effluent and satisfied the national standard of drinking water. The extraction process included chemical reaction.

Syntheses and Characterizations of Luminescent Complexes [(BINAP)Pt(C≡CC_6H_4R-p)_2] (R = H, 1; CH_3, 2) (BINAP = 2,2’-Bis(diphenylphosphino)-1,1’-binaphthyl)

[（BINAP）Pt（C≡CC6H4R-p）2] （R = H, 1; CH3, 2） （BINAP = 2,2＇-bis（diphenylphosphino）-1,1＇-binaphthyl） were synthesized and characterized by X-ray crystallography. Complex 1 crystallizes in triclinic, space group P1^- with a = 11.699（3）, b = 12.512（3）, c = 15.611（4） ,A^°, α= 93.277（3）, β= 97.626（2）, γ = 97.375（14）°, V = 2239.9（9） ,A^°3, Mr = 1014.92, Z = 2, Dc = 1.505 g/cm^3, F（000） = 1010,μ（MoKα） = 3.244 mm^-1, the final R = 0.0338 and wR = 0.0905 for 7738 observed reflections （1 〉 2σ（I））. Complex 2 crystallizes in monoclinic, space group P2（1/n） with a = 18.03690 （10）, b = 13.06060（10）, c = 21.6913（3） A^°,β= 96.5430（10）°, V= 5076.60（9） A^3, Mr = 1132.94, Z = 4, Dc = 1.482 g/cm^3, F（000） = 2272,μ（MoKα） = 2.973 mm^-1, the final R = 0.0481 and wR = 0.0893 for 8916 observed reflections （1 〉 2σ（I））. Both complexes emit intensively photoluminescence in both solid state and fluid solution due to MLCT （Pt→C≡CC6H4R-p） emissive state.

Synthesis and characterization of N,N-(pyromellitoyl)-bis-L-phenylalanine diacid ester butynediol

N,N-（pyromellitoyl）-bis-L-phenylalanine diacid ester butynediol（PBDCB）from pyromellitic dianhydride（PMDA）,butynediol（2-butyne-1,4-diol）and DL-phenylalanine（DLP）was synthesized.The PBDCB can be used as chain extender for thermoplastic polyurethane.The starting material of N,N-（pyromellitoyl）-bis-L-phenylalanine diacid（PBD）was synthesized through addition reaction between PMDA and DLP.Then,PBD was esterified using triethylamine as catalyst and attached antacids as well as dimethylacetamide（DMAc）as solvent.The obtained PBDCB was characterized using Fourier transformed infrared spectroscopy（FTIR）,nuclear magnetic resonance（1 H NMR）spectroscopy,mass spectrometry（MS）,thermal gravimetric（TG）,and differential scanning calorimetry（DSC）.The results showed that the PBDCB was highly thermal stable.

Synthesis,Structure and Photophysical Properties of Heteronuclear Pt_2Cu Alkynyl Complexes

Two luminescent hetero-trinuclear complexes [Pt2Cu（μ-dpppy）2（C≡CC6H4R-4）4]（Cl O4）（R = H,1;R = CH3,2;dpppy = 2,6-bis（diphenylphosphino）pyridine） have been synthesized and characterized by elemental analyses,ESI-MS,^1H and ^31P{^1H} NMR spectroscopy,and X-ray crystallography for 2.Their photophysical properties in the solid state and in solutions at room temperature and in frozen glasses at 77 K were studied.Both complexes 1 and 2 show strong orange-red emission in the solid state at room temperature and in frozen glasses at 77 K,and weak emission in solutions.

Recent Expedition in Pd-Catalyzed Sonogashira Coupling and Related Processes

Sonogashira cross-coupling protocol,typically showing the reaction between aryl/vinyl halide and terminal alkyne,has been a widely used protocol for constructing C(sp2)-C(sp)bond.The resulting internal alkynes are highly versatile for reaching differently function-alized alkyne-containing scaffolds or serving as valuable synthetic synthons to many other functional groups.It is worth noting that products originated from this coupling reaction are mostly applicable to be transformed into corresponding Z-alkene,alkane,or het-erocyclic moieties in natural product syntheses.The reaction conditions and catalyst systems are able to be tweaked in order to facil-itate the activation of steric hindered and/or electron-rich electrophiles.Pd-catalyzed copper-free Sonogashira coupling reaction has caught increasing attention as the improved method can be more environmentally friendly.What is more,the conditions of the cou-pling reaction can be readily amended to allow the fusion of other carbonylation or decarboxylation step in the catalytic cycle,and thus allow more complex yet versatile convergent synthesis to proceed in an operationally simple one-pot manner.