26981-81-7Relevant academic research and scientific papers
Atomically dispersed Rh on hydroxyapatite as an effective catalyst for tandem hydroaminomethylation of olefins
Gun, Gong,Li, Liusha,Li, Xiao,Lin, Tiejun,Qin, Tingting,Zhong, Liangshu
, (2021/07/07)
Tandem hydroaminomethylation is an efficient and green route for one-pot synthesis of amines directly from olefins. Herein, heterogeneous hydroxyapatite (HAP) supported single-atom Rh catalyst was prepared and used for tandem hydroaminomethylation of olefins. Characterization techniques confirmed the atomic dispersion of Rh species on HAP. Up to 99% conversion of 1-hexene with high selectivity to the desired amines (93.2%) was obtained over 0.5Rh1/HAP catalyst. Mechanism study demonstrated that the first hydroformylation step during the tandem catalytic process was rate-determining. Compared with the Rh nanoparticles on other oxide supports (Mg3Al, MgO and Al2O3), the atomically dispersed Rh sites on HAP ensured the high hydroformylation activity, thereby guaranteed the outstanding catalytic performance for the total tandem process. Furthermore, various corresponding amines can be obtained with satisfactory yields over 0.5Rh1/HAP catalyst from a wide scope of olefins or amines substrates.
Photometric Characterization of the Reductive Amination Scope of the Imine Reductases from Streptomyces tsukubaensis and Streptomyces ipomoeae
Matzel, Philipp,Krautschick, Lukas,H?hne, Matthias
, p. 2022 - 2027 (2017/10/07)
Imine reductases (IREDs) have emerged as promising enzymes for the asymmetric synthesis of secondary and tertiary amines starting from carbonyl substrates. Screening the substrate specificity of the reductive amination reaction is usually performed by time-consuming GC analytics. We found two highly active IREDs in our enzyme collection, IR-20 from Streptomyces tsukubaensis and IR-Sip from Streptomyces ipomoeae, that allowed a comprehensive substrate screening with a photometric NADPH assay. We screened 39 carbonyl substrates combined with 17 amines as nucleophiles. Activity data from 663 combinations provided a clear picture about substrate specificity and capabilities in the reductive amination of these enzymes. Besides aliphatic aldehydes, the IREDs accepted various cyclic (C4–C8) and acyclic ketones, preferentially with methylamine. IR-Sip also accepted a range of primary and secondary amines as nucleophiles. In biocatalytic reactions, IR-Sip converted (R)-3-methylcyclohexanone with dimethylamine or pyrrolidine with high diastereoselectivity (>94–96 % de). The nucleophile acceptor spectrum depended on the carbonyl substrate employed. The conversion of well-accepted substrates could also be detected if crude lysates were employed as the enzyme source.
Rhodium exchanged ETS-10 and ETS-4: Efficient heterogeneous catalyst for hydroaminomethylation
Sudheesh,Shukla, Ram S.
, p. 116 - 124 (2014/02/14)
Rhodium exchanged titanosilicates (ETS-10 and ETS-4) were synthesized and found to be efficient and stable catalysts for hydroaminomethylation reaction. The catalyst was highly active and selective towards amine product within lower reaction time of 4 h. 1-Hexene and pyrrolidine were taken as representative substrates for parametric variations using Rh-ETS-10. The increase in pyrrolidine ratio gave some significant information showing a decrease in conversion with increased selectivity. The reason may be the competition between pyrrolidine and 1-hexene for coordination sites in rhodium and which prevents the beta-hydride elimination. The ratios of H2 and CO have influenced hydroaminomethylation and the best performance was in the CO:H2 ratio of 1:4 under the studied conditions. The initial rate of formation of amine was double than that of isomerization of 1-hexene. The Rh cluster like complex was formed on treating the catalyst with syn gas. A homogenous- heterogeneous dual nature of Rh was found during hydroaminomethylation. The catalyst was effectively recycled for three times without much loss in its activity and selectivity.
Rhodium complex encapsulated functionalized hexagonal mesoporous silica for heterogeneous hydroaminomethylation
Sudheesh,Shukla, Ram S.
, p. 159 - 166 (2013/03/28)
HRh(CO)(PPh3)3 complex was encapsulated into the pores of amino functionalized hexagonal mesoporous silica. The catalyst was characterized by physico-chemical techniques like P-XRD, 31P-CPMAS NMR, FT-IR, SEM, ICP and N2 adsorption analysis. The catalyst was active for hydroaminomethylation and a variety of alkenes and amines were used as reactants for hydroaminomethylation. The catalyst afforded to achieve 100% conversion with high (>95%) selectivity to corresponding amines. Parametric variations were performed by taking 1-hexene and morpholine as representative reactants for the study of catalyst amount, temperature, pressure and 1-hexene:morpholine ratio. Significant amounts of aldehydes and enamines were observed during the course of the reaction indicating that there could be two possible rate determining steps. The catalyst was effectively recycled up to five times without much loss in its activity and selectivity.
Selective hydroaminomethylation of olefins using simple and efficient Rh-phosphinite complex catalyst
Khan, Shoeb R.,Bhanage, Bhalchandra M.
, p. 711 - 715 (2013/12/04)
Hydroaminomethylation of various olefins with primary and secondary amines was carried out using a simple and efficient rhodium-phosphinite complex catalyst. The influence of various reaction parameters including the effects of temperature, pressure, catalyst loading, time and solvents has been investigated. The present protocol is general with wider substrate applicability for the synthesis of an important class of aliphatic amines and arylethylamines. High activity and selectivity for amines was achieved with a very good substrate/catalyst molar ratio (turnover number 2500) under mild reaction conditions. Copyright
