TsNBr2 promoted decarboxylative bromination of α,β-unsaturated carboxylic acids

A rapid process for decarboxylative bromination of α,β-unsaturated carboxylic acids have been developed using N,N-dibromo-p-toluenesulfonamide (TsNBr₂). Treatment of cinnamic acids with TsNBr₂ in presence of potassium carbonate in acetonitrile produces corresponding β-bromostyrenes at room temperature. Exclusive formation of (E)-β-bromostyrenes was observed in a stereoselective manner within a very short period of time (5–15?min). This method was further extended for obtaining 1-bromoalkynes from corresponding propiolic acids. Instantaneous formation of bromoalkynes was observed when the reaction was carried out in presence of DBU as a base in acetonitrile at room temperature. A wide variety of cinnamic acids and propiolic acids could be converted to corresponding β-bromostyrenes and 1-bromoalkynes respectively under mild reaction condition with high to excellent yield.     

Palladium‐Catalyzed,tert‐Butyllithium‐Mediated Dimerization of Aryl Halides and Its Application in the Atropselective Total Synthesis of Mastigophorene A

A palladium‐catalyzed direct synthesis of symmetric biaryl compounds from aryl halides in the presence of tBuLi is described. In situ lithium–halogen exchange generates the corresponding aryl lithium reagent, which undergoes a homocoupling reaction with a second molecule of the aryl halide in the presence of the palladium catalyst (1 mol %). The reaction takes place at room temperature, is fast (1 h), and affords the corresponding biaryl compounds in good to excellent yields. The application of the method is demonstrated in an efficient asymmetric total synthesis of mastigophorene A. The chiral biaryl axis is constructed with an atropselectivity of 9:1 owing to catalyst‐induced remote point‐to‐axial chirality transfer.     

Dehydrogenative Homocoupling of Terminal Alkenes on Copper Surfaces: A Route to Dienes

Homocouplings of hydrocarbon groups including alkynyl (sp¹), alkyl (sp³), and aryl (sp²) have recently been investigated on surfaces with the interest of fabricating novel carbon nanostructures/nanomaterials and getting fundamental understanding. Investigated herein is the on‐surface homocoupling of an alkenyl group which is the last elementary unit of hydrocarbons. Through real‐space direct visualization (scanning tunneling microscopy imaging) and density functional theory calculations, the two terminal alkenyl groups were found to couple into a diene moiety on copper surfaces, and is contrary to the common dimerization products of alkenes in solution. Furthermore, detailed DFT‐based transition‐state searches were performed to unravel this new reaction pathway.     

Synthesis of (E)-prop-1-ene-1,3-diyldibenzene derivatives via direct decarboxylative coupling of α,β-unsaturated carboxylic acids with benzyl boronic acid pinacol ester

The first copper-catalyzed cross-coupling reaction between benzyl boronic acid pinacol ester and α,β-unsaturated carboxylic acids was described. The ready availability of the starting materials and excellent E selectivity make this protocol a safe and operationally convenient strategy for the efficient synthesis of (E)-prop-1-ene-1,3-diyldibenzene derivatives.     

Pd-catalyzed decarboxylative cross-coupling of sodium pyrimidinecarboxylates with (hetero)aryl bromides

A straightforward method for the synthesis of functionalized 4- or 5-(hetero)arylpyrimidines via decarboxylative cross-coupling reaction from readily available pyrimidine-4- and pyrimidine-5-carboxylates was described. In the presence of dual-catalyst system of Pd(PPh₃)₄/Cu₂O, the reaction proceeds smoothly, tolerates a variety of functional groups, and provides easy access to the synthesis of different (hetero)arylpyrimidines compounds.     

6,6'-二甲基-2,2'-联吡啶-4,4'-二甲酸甲酯的合成与表征

以6-甲基-2-羟基吡啶-4-甲酸甲酯为起始原料,经酯化反应制备2-甲基-6-(对甲苯磺酰氧基)吡啶-4-甲酸甲酯,使其在过渡金属镍络合物催化作用下自身偶联合成6,6'-二甲基-2,2'-联吡啶-4,4'-二甲酸甲酯,通过改变投料比例、反应温度及投料顺序获得最佳反应条件,收率77%。经核磁共振、红外光谱、质谱及差示扫描热量法等对分子结构进行了表征,验证了合成方法的可靠性。该结构能够满足均相时间分辨荧光免疫分析螯合剂中间体的需求。目前,它已成功用于均相时间分辨荧光免疫分析。     

Synthesis of symmetrical diarylalkyne from palladium-catalyzed decarboxylative couplings of propiolic acid and aryl bromides under water

Symmetric diarylalkynes were obtained from the decarboxylative coupling reactions of aryl bromides and propiolic acid in water solvent condition. In the presence of phase transfer surfactant C₁₈H₃₇N(CH₃)₃Cl, the catalytic system of both Pd(PPh₃)₂Cl₂/dppb and Pd(TPPMS)₂Cl₂/TPPMS afforded the desired coupled products in good yields.     

Tandem Pd/C‐Catalyzed Reductive Coupling and Dehalogenation of Benzylic Halides

High‐yield reductive homocoupling of benzotrichloride and benzal chloride followed by consecutive reductive dechlorination to 1,2‐dichlorostilbene and stilbene is effected in the presence of sodium formate as the reducing agent and Pd/C catalysts.     

Silver-catalyzed decarboxylative homocoupling reaction for the construction of tetrafluoroethylene-bridging aromatic compounds

The Ag(I)-catalyzed decarboxylative homocoupling from the difluoroacetate has been developed to the synthesis of symmetric CF₂–CF₂ containing dimers. This radical dimerization overpasses the prefunctionalization of the substrate and provides a direct and efficient method for construction of tetrafluoroethylene bridge-linked homodimers.