钯催化下活性亚甲基化合物的烯丙基化相转移反应

钯催化下活性亚甲基化合物的烯丙基化反应在有机合成中是一种十分有用的方法。例如在双三苯基膦二氯化钯催化下丙二酸二乙酯、α-砜基乙酸乙酯等活性亚甲基化     

Double Carbonylation of Organohalogen Compounds Catalyzed by Polymer-Bound Palladium Complexes

Palladium complex-catalyzed double carbonylation is a recently discovered reaction in organotransition metal chemistry. In this paper, some polymer-bound palladium complexes-polystyrylphosphine-palladium(0) complexes, poly-2-vinylpyridine-palladium(II) complexes, and poly-2-Af-vinylpyrrolidone-palladium(II) complexes have been prepared and characterized. The complexes were tested as catalysts in the double carbonylation reaction. Among these catalysts, polystyrylphos-phine-palladium(0) complexes showed good activity and selectivity, and can be easily recovered and reused. The influence of experimental parameters was investigated as well.     

Enantioselective Aldol Reaction with Difluoroenoxysilanes Catalyzed by Cationic Palladium Aqua Complexes

The enantioselective addition of difluoroenoxysilanes to aromatic aldehydes, catalyzed by cationic palladium aqua complexes, has been described. The reaction is operationally simple, does not require anhydrous conditions and performs at room temperature. The palladium catalysts, previously discovered and reported by Sodeoka, are easily prepared in two steps from PdCl₂(MeCN)₂. The aldol compounds were obtained in good yields and with enantiomeric ratios up to 93 : 7, the reaction being more efficient using electron-rich aldehydes.     

A Direct Amination of Isoprene by Aniline – Catalyzed by Palladium Complexes

The reaction of isoprene with aniline, catalyzed by Pd (acac)₂–(RO)₃P‐CF₃COOH, (1:4:4) (R = Me, Et, acac = (CH₃CO)₂CH‐) in MeCN solution, results in high (up to 89 mol.%) selectivity of N–(3‐methyl‐2‐buten‐1‐yl) aniline. The presence of telomeric products in the reaction mixture is observed at a P/Pd ratio of 1:2 and 1:1. The use of (1,1,1‐trifluoro, 4‐perfluorocyclo hexyl ‐2,4‐butanedionato) palladium as the catalyst gives rise to 92 mol% mol.selectivity of telomers by the favored tail‐to‐head and head to head coupling.     

溴化钯或乙酰丙酮羰基铑/手性配体催化醛与乙酰胺的不对称酰胺羰化反应研究

采用溴化钯为催化剂前体,与非螯合型双齿膦配体L1(DPPFF)、联吡啶型双齿膦配体L2(P-PHOS)和二茂铁基手性双膦配体L3((S,Rp)-BPPF)制备络合物催化剂,以乙酰丙酮羰基铑为催化剂前体,与手性亚磷酸酯配体L4-L6制备络合物催化剂,将其分别应用于底物环己基甲醛或苯乙醛的不对称酰胺羰化反应中,研究结果表明...     

Rh(Xantphos)L催化氢化肉桂醛和降冰片二烯间转移加氢甲酰化反应的理论研究

采用密度泛函理论方法 M11-L/6-31G(d,p)对氢化肉桂醛与降冰片二烯(nbd)在活化催化剂a[Rh(Xantphos)L,L=苯甲酸根,Xantphos=4,5-双二苯基膦-9,9-二甲基氧杂蒽]催化下发生转移加氢甲酰化反应生成主产物苯乙烯(3)的反应机理进行理论研究.结果表明,参与反应的醛类化合物在α碳(α-C)上应至少连接一个氢原子,这可以减少醛类反应物和抗衡离子的空间排斥作用.通过反应能垒图可见,受体nbd发生加氢甲酰化反应,促进了脱氢甲酰化反应的进行,进而促使整个转移加氢甲酰化循环不可逆进行.还研究了氢化肉桂醛发生脱羰化生成少量副产物苯乙烷(4)的机理过程.结果表明,苯甲酸根作为抗衡离子抑制了脱羰化反应的竞争,理论计算得到脱氢甲酰化反应的选择性为苯乙烯(3)∶苯乙烷(4)99∶1.简单醛(如丙醛)在活化催化剂a催化下更易于发生脱羰反应而不是脱氢甲酰化反应.     

钯体系催化苯乙烯区域选择氢酯化反应中金属氯化物的助剂效应

原位制备的一和纱列钯体系催化剂,在苯乙烯、一氧化碳、甲醇氢酯化反应中显示出良好的反应活性及较大差异的区域选择性。不同的金属氯化物助催化剂,对反应活性及区域选择性影响很大,而在相同条件下选择其它类型的金属盐类,如醋酸盐,则导致催化活性完全丧失。     

Intermolecular Methoxycarbonylation of Terminal Alkynes Catalyzed by Palladium(II) Bis(oxazoline) Complexes

Boxing clever : Direct conversion of a terminal alkyne group into a β‐methoxyacrylate is realized with the aid of the bis(oxazoline) ligand (box). Acetyl and ketal protecting groups, free hydroxy groups, and acid‐sensitive glycosidic bonds are not affected under the reaction conditions. The one‐pot synthesis of (±)‐dihydrokawain from the homopropargyl alcohol is also achieved. tfa=trifluoroacetate

     

Carbonylation of Difluoroalkyl Bromides Catalyzed by Palladium

Although important progress has been made in the fluoroalkylation reactions, the transition‐metal‐catalyzed carbonylative fluoroalkylation reaction remains challenging so far. Herein, we report the first example of a Pd‐catalyzed carbonylation of difluoroalkyl bromides with (hetero)arylboronic acids under one atmosphere pressure of CO. The reaction can also be extended to the aryl potassium trifluoroborate salts. The advantages of this protocol are synthetic simplicity, broad substrate scope, and excellent functional group compatibility. The resulting difluoroalkyl ketones can serve as versatile building blocks for the synthesis of various useful fluorinated compounds.     

Hydrophosphorylation of Terminal Alkynes Catalyzed by Palladium

A series of new 1-aryl-, 1-heteroaryl-, and 1-alkylethenylphosphonates was prepared by hydrophosphorylation of terminal acetylenes catalyzed by palladium. A stable in air complex Pd₂(dba)₃·CHCl₃ was applied as catalyst. The reaction mechanism is discussed.     

Arylation of Substituted Anilines Catalyzed by Palladium

Arylation catalyzed by palladium complexes of substituted anilines obtained by modification of 2,4,6-trinitrotoluene makes possible preparation of various diaryl- and arylheterylamines in high yields.     

Studies on Suzuki‐Miyaura Reactions Catalyzed by Ferrocenyl or Cobaltocenyl Phosphines Ligated Palladium Complexes

DFT studies on several dppf ‐ and dppc ‐derived bidentate phosphines ligated palladium complexes catalyzed Suzuki‐Miyaura coupling reactions were pursued. The catalytic reactions employing ligands, having two phosphine biting sites on different cyclpentadienyl or cyclobutadiene rings, such as 1,1′‐dmpf or 1,1′‐dmpc , have been verified to be energetically more favorable than those on the same ring provided that tetra‐coordinated palladium conformations for all transition states and intermediates are maintained. Apart from the purpose of storage, the application of phosphinous acid (R₂P(OH)) in Suzuki‐Miyaura reaction is inferior to tertiary phosphine (R₃P).     

Studies on Suzuki‐Miyaura Reactions Catalyzed by Ferrocenyl or Cobaltocenyl Phosphines Ligated Palladium Complexes

DFT studies on several dppf ‐ and dppc ‐derived bidentate phosphines ligated palladium complexes catalyzed Suzuki‐Miyaura coupling reactions were pursued. The catalytic reactions employing ligands, having two phosphine biting sites on different cyclpentadienyl or cyclobutadiene rings, such as 1,1'‐dmpf or 1,1' ‐dmpc, have been verified to be energetically more favorable than those on the same ring provided that tetra‐coordinated palladium conformations for all transition states and intermediates are maintained. Apart from the purpose of storage, the application of phosphinous acid (R₂P(OH)) in Suzuki‐Miyaura reaction is inferior to tertiary phosphine (R₃P).     

Addition of Bromotrichloromethane and Tetrachloromethane to cis-Cyclooctene,Cyclohexene, and Norbornadiene in the Presence of Palladium(II) Complexes

Addition of bromotrichloromethane and tetrachloromethane to alkenes in the presence of palladium(II) complexes begins with single-electron transfer from the palladium atom to polyhalomethane molecule, followed by fragmentation of the radical anion thus formed and generation of trichloromethyl radical. Halogen transfer to a carbon-centered radical arising from addition of trichloromethyl radical at the double bond occurs both from the polyhalomethane molecule and from halide palladium complex.     

Allylation of 5-Methylfurfural Catalyzed by Phase-Transfer Reagents in Aqueous Media

Allylation of 5-methylfurfural with allyl halide and zinc was performed by using quaternary ammonium and phosphonium salts as phase-transfer catalysts. The phosphonium salt showed higher activity than the ammonium salt. Excellent yields were obtained with both catalysts.     

Useful Sialic Acid Modifications Catalyzed by Palladium

A regio‐ and stereocontrolled solution for a selective modification at the C‐2 or C‐4 position of N‐acetylneuraminic acid involves the use of allylic substitution catalyzed by palladium. As illustrated in the scheme, regioselective malonylation is under the strict influence of the ligands associated with the allylpalladium complex.