Rh(I)-catalyzed cross-coupling reactions of alkenyl tosylates with potassium aryltrifluoroborates

RhCl(PPh₃)₃/DPPF was successfully employed as an efficient catalyst in the Suzuki-Miyaura cross-coupling reactions of potassium aryltrifluoroborates with alkenyl tosylates, affording the corresponding products in good to excellent yields.     

Synthesis of alkenylsilanes via palladium(0)-catalyzed silylation of alkenyl iodides with hydrosilane

Various alkenyl iodides were silylated with hydrosilanes in the presence of KOAc and a catalytic amount of Pd₂(dba)₃·CHCl₃ to afford the corresponding regio- and stereodefined (E)-alkenylsilanes in high yields.     

The palladium(II)-catalyzed Nazarov reaction

The PdCl(2)-catalyzed cyclization of alpha-alkoxy dienones leads to 2-hydroxycyclopentenones, whereas the Pd(OAc)(2)-catalyzed reaction leads to cross-conjugated cyclopentenones through an oxidative process. [reaction: see text]     

Diversity synthesis using the complimentary reactivity of rhodium(II)- and palladium(II)-catalyzed reactions

Rhodium(II)-catalyzed reactions of aryldiazoacetates can be conducted in the presence of iodide, triflate, organoboron, and organostannane functionality, resulting in the formation of a variety of cyclopropanes or C-H insertion products with high stereoselectivity. The combination of the rhodium(II)-catalyzed reaction with a subsequent palladium(II)-catalyzed Suzuki coupling offers a novel strategy for diversity synthesis.     

Effective Pd-nanoparticle (PdNP)-catalyzed Negishi coupling involving alkylzinc reagents at room temperature

Pd(OAc)(2) is an efficient catalyst precursor for Negishi coupling in the presence of Bu(4)NBr. Secondary and primary alkylzinc reagents with beta-H and arylzinc reagents all reacted with aryl iodides at temperatures as low as -20 degrees C, giving moderate to good yields. One example of coupling between alkynylzinc reagents and aryl iodides was tested and the yield was good. Preliminary kinetic studies indicated that the process involved PdNPs as the active catalytic species.     

Carbonylative Stille coupling reactions of benzyl chlorides with allyltributylstannane catalyzed by palladium nanoparticles

The carbonylative Stille coupling reaction of benzyl chlorides with allyltributylstannane was successfully conducted by using palladium nanoparticles as the catalyst under phosphine ligand-free conditions. The corresponding α,β-unsaturated ketone products were obtained in good to excellent yields.     

Cationic palladium(II)-catalyzed stereoselective glycosylation with glycosyl trichloroacetimidates

The development of a new method for stereoselective glycosylation with glycosyl trichloroacetimidate donors employing cationic palladium(II), Pd(CH(3)CN)(4)(BF(4))(2), is described. This process employs Pd(CH(3)CN)(4)(BF(4))(2) as an efficient activator, providing access to a variety of disaccharides and glycopeptides. This reaction is highly stereoselective and proceeds under mild conditions with low catalyst loading. Interestingly, this palladium catalysis directs beta-glucosylations in the absence of classical neighboring group participation.     

Copper(II)-catalyzed ortho-functionalization of 2-arylpyridines with acyl chlorides

Copper-catalyzed ortho-benzoxylation of 2-arylpyridine sp(2) C-H bonds with acyl chloride is described. Notably, switching the base from t-BuOK to Li(2)CO(3) causes chlorination of the C-H bond to take place.     

Copper-catalyzed coupling reactions of alkenyl halides with alkynes in the absence of palladium and ligand

We report herein copper(I)-catalyzed cross-coupling reactions of alkenyl halides with alkynes for the synthesis of 2-alkynyl-buta-1,3-dienes in good to excellent yields. This procedure is the first example for the synthesis of enynes catalyzed by catalytic amount of copper(I) alone in the absence of palladium and any ligand at relatively lower temperature.     

Efficient Negishi coupling reactions of aryl chlorides catalyzed by binuclear and mononuclear nickel-N-heterocyclic carbene complexes

We describe the first nickel-N-heterocyclic carbene catalyzed Negishi cross-coupling reaction of a variety of unactivated aryl chlorides, heterocyclic chlorides, aryl dichlorides, and vinyl chloride. The mononuclear and binuclear nickel-NHC complexes supported by heteroarene-functionalized NHC ligands are found to be highly efficient for the coupling of unactivated aryl chlorides and organozinc reagents, leading to biaryls and terphenyls in good to excellent yields under mild conditions. For all aryl chlorides, the binuclear nickel catalysts show activities higher than those of mononuclear nickel complexes because of possible bimetallic cooperative effect.     

Microwave-assisted aqueous Suzuki coupling reactions catalyzed by ionic palladium(II) complexes

Suzuki coupling is one of the most powerful methods for the synthesis of biaryls. We have prepared and characterized a series of unsymmetrical sulfonated water-soluble Pd(II)-pyridyl imine complexes and investigated them as catalysts for the Suzuki cross-coupling reaction in water under microwave irradiation. The compounds proved to be effective catalysts.     

Palladium(0)-catalyzed suzuki-miyaura cross-coupling reactions of potassium aryl- and heteroaryltrifluoroborates with alkenyl bromides

Efficient palladium(0)-catalyzed Suzuki-Miyaura cross-couplings are described. The reactions involving potassium aryl- and heteroaryltrifluoroborates with alkenyl bromides can generally be carried out using < or =2 mol % of palladium catalyst and 3 equiv of base in toluene/H2O. When stereodefined alkenyl bromides are employed, the resulting styrene derivatives are accessed stereospecifically. A variety of functional groups are tolerated in both coupling partners.     

纳米钯催化苄基氯代物与烯丙基硼酸频哪醇酯的羧化Suzuki偶联反应

CO2是廉价的C1源,同时具有无毒、储量丰富的优点, 符合绿色化学发展要求. 利用 CO2构筑新的 C–C 键是化学固定CO2的重要方法. Β,γ-不饱和酯类结构单元是许多生物活性分子的重要组成部分, 经由双π-烯丙基钯中间体与 CO2反应, 合成新的β,γ-不饱和酯类化合物, 具有重要意义. CO2与有机硼化合物的羧化反应已有报道, 有机硼化合物具有低毒、对水不敏感等优点. 但是已报道的羧化 Suzuki 偶联反应存在诸多缺点: (1) 需要使用含膦或者氮杂环卡宾配体的催化剂, 而这些催化剂的制备过程使前期实验步骤变得冗长, 同时反应液的酸化后处理过程也会造成环境污染; (2) 有机硼试剂的官能团兼容范围窄, 限制了底物范围的拓展. 本课题组以原位生成的纳米钯粒子为催化剂, 在 CO2存在的温和条件下, 高效实现了苄氯与烯丙基硼酸频哪醇酯的羧化 Suzuki 偶联反应. 反应过程中无其它配体加入, 反应结束后不需要酸化或酯化的后处理过程. 该反应将具有广泛的官能团兼容性.本文以 TBAB 稳定的纳米钯粒子为催化剂, 在温和条件下, 实现了氯甲基芳香化合物、烯丙基硼酸频哪醇酯和 CO2的三组分羧化 Suzuki 偶联反应. 最佳反应条件为: Pd(acac)2(5 mol%)、TBAB (0.7 mmol, 1.4 equiv.)、KF (1 mmol, 2.0 equiv.)、苄基卤代物 (0.5 mmol)、烯丙基硼酸频哪醇酯 (0.6 mmol, 1.2 equiv.)、CO2(2.0 Mpa)、溶剂 THF (5 mL), 50 oC 反应 24 h. 在最佳反应条件下, 苯环、萘环以及杂芳环的氯甲基化合物均可发生该羧化反应. 苯环上取代基的位置对产物的收率有影响. 当使用 1-溴甲基萘作为底物时反应也能够发生, 收率与 1-氯甲基萘作为底物时的收率相当. 与已报道有机硼试剂的羧化反应相比, 该反应体系无需加入配体, 原位生成了纳米钯粒子, 避免了催化剂或者配体的复杂制备过程. 该反应中, 氟离子的存在是必要的, 对烯丙基硼酸频哪醇酯具有活化作用.     

New palladium(II)-catalyzed asymmetric 1,2-dibromo synthesis

[reaction: see text] The oxidation of olefins by chiral monometallic and bimetallic Pd(II)-Cu(II) catalysts in bromide-containing aqueous-THF reaction mixtures produced chiral 1,2-dibromides. With alpha-olefins, the ee's were about 95% while most of the internal alkenes gave somewhat lower enantioselectivities ( approximately 80%).     

The renaissance of palladium(II)-catalyzed oxidation chemistry

Palladium(II)-catalyzed oxidations constitute a paramount reaction class but have remained immature over the past few decades. Recently, this field has reappeared at the forefront of organometallic catalysis. This emerging area article outlines recent developments in palladium(II)-catalyzed oxidation chemistry with discussion of potential future growth.     

Cu(II)-catalyzed oscillatory chemical reactions

The role of copper ions in the copper-catalyzed chemical reactions is discussed. It is pointed out that copper ions can induce oscillatory behavior in many systems for the following reasons: (1) Copper cations can exist in three oxidation states (+1, +2 and +3); (2) Copper cations can form precipitates and stable complexes with a large number of reactants and intermediates; (3) Copper ions can participate in both oxidation and reduction processes, due to the surprisingly large range of redox potentials exhibited by the Cu²⁺/Cu⁺ and Cu³⁺/Cu²⁺ couples (known redox potentials span from 0.1 to 1.8 V, depending on the counter-ion or ligand present).     

Palladium(II)-catalyzed cycloisomerization of functionalized 1,5-hexadienes

Scope and limitations of the Pd(II)-catalyzed cycloisomerization of functionalized 1,5-hexadienes have been studied. In situ NMR experiments indicate a challenging competition between various reaction pathways. A careful balance between substrate structure, nature of the precatalyst, and reaction conditions was required to gain access to a useful building block for sesquiterpene total synthesis.