Ruthenium xantphos complexes in hydrogen transfer processes: reactivity and mechanistic studies
作者:Araminta E. W. Ledger、Paul A. Slatford、John P. Lowe、Mary F. Mahon、Michael K. Whittlesey、Jonathan M. J. Williams
DOI:10.1039/b813543f
日期:——
The in situ combination of [Ru(PPh3)3(CO)H2] with xantphos is catalytically active for the alkylation of alcohols with the ketonitriletBuC(O)CH2CN in a model oxidation–Knoevenagel–reduction process. The precursor complex [Ru(xantphos)(PPh3)(CO)H2] was isolated and reacted with stoichiometric amounts of PhCH2OH and PhCHO. Under these conditions, the alcohol is decarbonylated to afford [Ru(xantphos)(CO)2H2] and finally [Ru(xantphos)(CO)3], both of which prove to be less active for catalysis than the starting complex. The reactivity of the xantphos system contrasts with that of [Ru(dppp)(PPh3)(CO)H2], which is catalytically inactive for the Knoevenagel reaction and fails to show any stoichiometric reactivity with alcohols.
Imidazolium Ionic Liquids as Solvents for Cerium(IV)-Mediated Oxidation Reactions
作者:Hasan Mehdi、Andrea Bodor、Diána Lantos、István T. Horváth、Dirk E. De Vos、Koen Binnemans
DOI:10.1021/jo061909o
日期:2007.1.1
cerium salts as oxidizing agents was evaluated. Good solubility was found for ammonium hexanitratocerate(IV) (ceric ammonium nitrate, CAN) and cerium(IV) triflate in 1-alkyl-3-methylimidazolium triflate ionic liquids. Oxidation of benzyl alcohol to benzaldehyde in 1-ethyl-3-methylimidazolium triflate was studied by in-situ FTIR spectroscopy and 13C NMR spectroscopy on carbon-13-labeled benzyl alcohol. Careful
评估了咪唑鎓离子液体作为溶剂进行有机转化的过程,以四价铈盐为氧化剂。在六氟甲磺酸铵(IV)(硝酸硝酸铵,CAN)和三氟甲磺酸铈(IV)在1-烷基-3-甲基咪唑鎓三氟甲磺酸盐离子液体中发现了良好的溶解度。用原位FTIR光谱法研究了三氟甲磺酸1-乙基-3-甲基咪唑鎓中苄醇氧化为苯甲醛的方法,13碳13标记的苯甲醇的13 C NMR光谱。仔细控制反应条件是必要的,因为溶解在离子液体中的六偏硬脂酸铵(IV)不仅可以将苯甲醇转化为苯甲醛,而且还可以将苯甲醇转化为硝酸苄基或苯甲酸。三氟甲磺酸铈(IV)与苄醇在干燥的离子液体中反应的选择性取决于三氟甲磺酸铈(IV)的水合程度:无水三氟甲磺酸铈(IV)将苄醇转化为二苄醚,而水合铈(IV)三氟甲磺酸酯提供苯甲醛作为主要反应产物。已经研究了六偏乙酸铵(IV)与除苄醇以外的有机底物的反应。1,4-氢醌被定量转化为1,4-醌。苯甲醚和萘被硝化。
Metathesis Reaction of Diazo Compounds and <i>para</i>-Quinone Methides for C–C Double Bond Formation: Synthesis of Tetrasubstituted Alkenes and Quinolinones
作者:Bo Huang、Yangyong Shen、Zhenjun Mao、Yu Liu、Sunliang Cui
DOI:10.1021/acs.orglett.6b02365
日期:2016.10.7
The para-quinone methides (p-QMs) are activated by Lewis acid and then attacked by diazocompounds. The following rearrangement leads to nitrogen gas extrusion and C–C double bond formation to constitute a metathesis reaction process. Therefore, the diazoester is transformed into tetrasubstituted alkenes, whereas the diazo-oxindole delivers the quinolinone products. Furthermore, the 13C-labeling experiments
Catalytic Enantioselective [2,3]-Rearrangements of Allylic Ammonium Ylides: A Mechanistic and Computational Study
作者:Thomas H. West、Daniel M. Walden、James E. Taylor、Alexander C. Brueckner、Ryne C. Johnston、Paul Ha-Yeon Cheong、Guy C. Lloyd-Jones、Andrew D. Smith
DOI:10.1021/jacs.6b11851
日期:2017.3.29
A mechanistic study of the isothiourea-catalyzed enantioselective [2,3]-rearrangement of allylic ammonium ylides is described. Reaction kinetic analyses using 19F NMR and density functional theory computations have elucidated a reaction profile and allowed identification of the catalyst resting state and turnover-rate limiting step. A catalytically relevant catalyst–substrate adduct has been observed
Experimental and Theoretical Mechanistic Investigation of the Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols
作者:Esben P. K. Olsen、Thishana Singh、Pernille Harris、Pher G. Andersson、Robert Madsen
DOI:10.1021/ja5106943
日期:2015.1.21
decarbonylation of primary alcohols with the liberation of molecular hydrogen and carbon monoxide was studied experimentally and computationally. The reaction takes place by tandem catalysis through two catalytic cycles involving dehydrogenation of the alcohol and decarbonylation of the resulting aldehyde. The square planar complex IrCl(CO)(rac-BINAP) was isolated from the reaction between [Ir(cod)Cl]2, rac-BINAP
通过实验和计算研究了铱-BINAP 催化伯醇脱氢脱羰并释放分子氢和一氧化碳的机理。该反应通过串联催化通过两个催化循环进行,包括醇的脱氢和所得醛的脱羰。方形平面复合物 IrCl(CO)(rac-BINAP) 是从 [Ir(cod)Cl]2、rac-BINAP 和苯甲醇之间的反应中分离出来的。该复合物具有催化活性,可用于研究催化循环中的各个步骤。一个一氧化碳配体显示出在整个反应过程中与铱保持配位,并且表明从二羰基络合物中释放出一氧化碳。IrH2Cl(CO)(rac-BINAP) 也被合成并在苯甲醇的脱氢中检测到。在同一个实验中,从脱氢过程中 HCl 的释放以及随后与 IrCl(CO)(rac-BINAP) 的反应中检测到 IrHCl2(CO)(rac-BINAP)。这表明氯化物被醇取代以形成方形平面铱烷氧配合物,该配合物可以进行β-氢化物消除。脱羰的 KIE 为 1.0,整个反应的 KIE 为