排序方式: 共有172条查询结果,搜索用时 31 毫秒
31.
32.
A new series of titanium(IV) and zirconium(IV) amides have been prepared from the reaction between M(NMe2)4 (M = Ti, Zr) and C2-symmetric ligands, (R)-2,2′-bis(pyridin-2-ylmethylamino)-6,6′-dimethyl-1,1′-biphenyl (2H2), (R)-2,2′-bis(pyrrol-2-ylmethyleneamino)-6,6′-dimethyl-1,1′-biphenyl (3H2), (R)-2,2′-bis(diphenylphosphinoylamino)-6,6′-dimethyl-1,1′-biphenyl (4H2), (R)-2,2′-bis(methanesulphonylamino)-6,6′-dimethyl-1,1′-biphenyl (5H2), (R)-2,2′-bis(p-toluenesulphonylamino)-6,6′-dimethyl-1,1′-biphenyl (6H2), and C1-symmetric ligands, (R)-2-(diphenylthiophosphoramino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (7H) and (R)-2-(pyridin-2-ylamino)-2′-(dimethylamino)-6,6′-dimethyl-1,1′-biphenyl (8H), which are derived from (R)-2,2′-diamino-6,6′-dimethyl-1,1′-biphenyl. Treatment of M(NMe2)4 with 1 equiv. of N4-ligand, 2H2 or 3H2 gives, after recrystallization from an n-hexane solution, the chiral zirconium amides (2)Zr(NMe2)2 (9), (3)Zr(NMe2)2 (11), and titanium amide (3)Ti(NMe2)2 (10), respectively, in good yields. Reaction of Zr(NMe2)4 with 1 equiv of diphenylphosphoramide 4H2 affords the chiral zirconium amide (4)Zr(NMe2)2 (12) in 85% yield. Under similar reaction conditions, treatment of Ti(NMe2)4 with 1 equiv. of sulphonylamide ligand, 5H2 or 6H2 gives, after recrystallization from a toluene solution, the chiral titanium amides (5)Ti(NMe2)2·0.5C7H8 (13·0.5C7H8) and (6)Ti(NMe2)2 (15), respectively, in good yields, while reaction of Zr(NMe2)4 with 1 equiv. of 5H2 or 6H2 gives the bis-ligated complexes, (5)2Zr (14) and (6)2Zr (16). Treatment of M(NMe2)4 with 2 equiv. of diphenylthiophosphoramide ligand 7H or N3-ligand 8H gives, after recrystallization from a benzene solution, the bis-ligated chiral zirconium amides (7)2Zr(NMe2)2 (17) and (8)2Zr(NMe2)2 (19), and bis-ligated chiral titanium amide (8)2Ti(NMe2)2 (18), respectively, in good yields. All new compounds have been characterized by various spectroscopic techniques, and elemental analyses. The solid-state structures of complexes 10, 12, 13, and 17-19 have further been confirmed by X-ray diffraction analyses. The zirconium amides are active catalysts for the asymmetric hydroamination/cyclization of aminoalkenes, affording cyclic amines in good to excellent yields with moderate ee values, while the titanium amides are not. 相似文献
33.
Gribkov DV Hultzsch KC Hampel F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(19):4796-4810
Monomeric diolate amido yttrium complexes [Y[diolate][N(SiHMe(2))(2)](thf)(2)] can be prepared in good yield by treating [Y[N(SiHMe(2))(2)](3)(thf)(2)] with either 3,3'-di-tert-butyl-5,5',6,6'-tetramethyl-1,1'-biphenyl-2,2'-diol (H(2)(Biphen)), 3,3'-bis(2,4,6-triisopropylphenyl)-2,2'-dihydroxy-1,1'-dinaphthyl (H(2)(Trip(2)BINO)) or 3,3'-bis(2,6-diisopropylphenyl)-2,2'-dihydroxy-1,1'-dinaphthyl (H(2)(Dip(2)BINO)) in racemic and enantiopure form. The racemic complex [Y(biphen)[N(SiHMe(2))(2)](thf)(2)] dimerizes upon heating to give the heterochiral complex (R,S)-[Y(biphen)[N(SiHMe(2))(2)](thf)](2). The corresponding dimeric heterochiral lanthanum complex was the sole product in the reaction of H(2)(Biphen) with [La[N(SiHMe(2))(2)](3)(thf)(2)]. Single-crystal X-ray diffraction of both dimeric complexes revealed that the two Ln(biphen)[N(SiHMe(2))(2)](thf) fragments are connected through bridging phenolate groups of the biphenolate ligands. The two different phenolate groups undergo an intramolecular exchange process in solution leading to their equivalence on the NMR timescale. All complexes were active catalysts for the hydroamination/cyclization of aminoalkynes and aminoalkenes at elevated temperature, with [Y((R)-dip(2)bino)[N(SiHMe(2))(2)](thf)(2)] being the most active one giving enantioselectivities of up to 57 % ee. Kinetic resolution of 2-aminohex-5-ene proceeded with this catalyst with 6.4:1 trans selectivity to give 2,5-dimethylpyrrolidine with a k(rel) of 2.6. 相似文献
34.
The inter- and intramolecular addition of nitrogen pronucleophiles to methylenecyclopropanes proceeds smoothly in the presence of palladium catalyst, giving the corresponding hydroamination products in good to excellent yields. The reaction proceeds mainly through cleavage of a distal bond of methylenecyclopropanes. 相似文献
35.
Dr. Jérôme Hannedouche Dr. Emmanuelle Schulz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(16):4972-4985
Asymmetric hydroamination allows the direct and selective formation of a new C? N bond as a simple procedure towards valuable scalemic synthons. Huge efforts have recently been made to overcome the challenges associated with this transformation. This non‐comprehensive Concept article aims at pointing out the most recent and original progresses, offering nearby developments, and addressing the next challenges. 相似文献
36.
Unusual NHC–Iridium(I) Complexes and Their Use in the Intramolecular Hydroamination of Unactivated Aminoalkenes
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gellért Sipos Arnold Ou Prof. Brian W. Skelton Dr. Laura Falivene Prof. Luigi Cavallo Prof. Reto Dorta 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6939-6946
N‐heterocyclic carbene (NHC) ligands with naphthyl side chains were employed for the synthesis of unsaturated, yet isolable [(NHC)Ir(cod)]+ (cod=1,5‐cyclooctadiene) complexes. These compounds are stabilised by an interaction of the aromatic wingtip that leads to a sideways tilt of the NHC?Ir bond. Detailed studies show how the tilting of such N‐heterocyclic carbenes affects the electronic shielding properties of the carbene carbon atom and how this is reflected by significant upfield shifts in the 13C NMR signals. When employed in the intramolecular hydroamination, these [(NHC)Ir(cod)]+ species show very high catalytic activity under mild reaction conditions. An enantiopure version of the catalyst system produces pyrrolidines with excellent enantioselectivities. 相似文献
37.
Synthetic Efforts toward the Lycopodium Alkaloids Inspires a Hydrogen Iodide Mediated Method for the Hydroamination and Hydroetherification of Olefins
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Paul R. Leger Rebecca A. Murphy Eugenia Pushkarskaya Prof. Richmond Sarpong 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(11):4377-4383
Progress toward the total syntheses of a diverse set of fawcettimine‐type Lycopodium alkaloids via a “Heathcock‐type” 6–5–9 tricycle is disclosed. This route features an intermolecular Diels–Alder cycloaddition to rapidly furnish the 6–5‐fused bicycle and a highly chemoselective directed hydrogenation to build the azonane fragment. While conducting these synthetic studies, trimethylsilyl iodide was found to effect a hydroamination reaction to furnish the tetracyclic core of serratine and related natural products. This observation has been expanded into a general method for the room temperature hydroamination of unactivated olefins with tosylamides utilizing catalytic “anhydrous” HI (generated in situ from trimethylsilyl iodide and water). The presence of the iodide anion is critical to the success of this Brønsted acid catalyzed protocol, possibly due to its function as a weakly coordinating anion. These conditions also effect the analogous hydroetherification reaction of alcohols with unactivated olefins. 相似文献
38.
39.
Dr. Florian F. Mulks Leonie J. Bole Dr. Laia Davin Dr. Alberto Hernán-Gómez Alan Kennedy Dr. Joaquín García-Álvarez Prof. Dr. Eva Hevia 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(43):19183-19188
A straightforward alkali-metal-mediated hydroamination of styrenes using biorenewable 2-methyltetrahydrofuran as a solvent is reported. Refuting the conventional wisdom of the incompatibility of organolithium reagents with air and moisture, shown here is that the presence of moisture is key in favoring formation of the target phenethylamines over competing olefin polymerization products. The method is also compatible with sodium amides, with the latter showing excellent promise as highly efficient catalysts under inert atmosphere conditions. 相似文献
40.
Surya Prakash Singh T. Vijaya Kumar M. Chandrasekharam L. Giribabu P. Yella Reddy 《合成通讯》2013,43(22):3982-3989
Highly efficient solvent-free aza-Michael additions of a variety of amines to α,β-unsaturated carbonyl compounds under microwave-irradiation conditions catalyzed by perchloric acid impregnated on silica gel (HClO4/SiO2) is reported. The reactions are completed within 2–7 min in a microwave oven to produce the corresponding adducts in excellent yields, and the catalyst can be recovered and reused. 相似文献