A new type of planar chiral Shvo catalysts, where the chirality is based solely on different substitution flanking the C O function, was prepared and used for transfer hydrogenation of imines and ketones. The reduction of ketimines represented by N‐(1‐phenylethylidene)aniline and prochiral ketones such as phenyl trifluoromethyl ketone with 2‐propanol was efficiently catalyzed by 0.5 mol% of the chiral Shvo catalyst to give high yields of the corresponding reduction products with the enantioselectivities in the range 45% to 64% ee.
A zeolite-encapsulated cobalt salophen catalyst was prepared by the intrazeolite ligand synthesis method. This catalyst proved to be active in the ruthenium-catalyzed oxidation of primary and secondary alcohols to aldehydes or ketones. Several advantages of the heterogenized catalyst was found in this system compared to the homogeneous counterpart, namely easy handling and better performance (less sensitive to solvent effects, higher specific rates). 相似文献
Sodium ruthenate was supported on 2% and 25% cross-linked poly(4-vinylpyridine). These compounds were found to be efficient
and selective catalysts for the room temperature oxidation of internal and external alcohols to aldehydes and ketones, respectively.
The catalysts were active with a wide range of co-oxidants and no over-oxidation products were observed. 相似文献
An oxidant‐free dehydrogenation of alcohols in the aqueous phase was developed for the first time using water‐soluble poly(N‐vinyl‐2‐pyrrolidone) (PVP)‐stabilized ruthenium nanoparticles with an ionic liquid as a promoter. The present catalytic system was highly efficient and stable for the catalytic dehydrogenation of various alcohols. It was found that the basic ionic liquid 1‐n‐butyl‐2,3‐dimethylimidazolium acetate ([BMMIM] OAc) additive played a crucial role in enhancing the catalytic activity and stability of ruthenium(0) nanoparticles. A reaction kinetics study and 1H NMR analysis demonstrated that the basic ionic liquid and ruthenium nanoparticles exerted a synergetic effect for the dehydrogenation reaction. 相似文献
The oxidation of alcohols to aldehydes and ketones has been described using silica‐supported vanadium(IV ) oxide (V/SiO2, 1 ) in the presence of tert‐butyl hydroperoxide in tert‐butyl alcohol at ambient temperature with quantitative yields. The procedure is simple, efficient and environmentally benign. 相似文献
Dehydrogenative coupling of primary alcohols with secondary amines to form tertiary amides and dihydrogen (H2) is efficiently catalyzed by bipyridyl‐based ruthenium pincer complexes (0.2–1 mol%) under neutral conditions (in case of the dearomatized complexes), or with added catalytic amount of base. The reaction is sensitive to steric hindrance; in the case of amidation of bulky secondary amines a less sterically hindered complex is more efficient. Selective acylation of primary amines in the presence of secondary amines was also demonstrated.
New 3rd generation designer ansa‐ruthenium(II) complexes featuring N,C‐alkylene‐tethered N,N‐dialkylsulfamoyl‐DPEN/η6‐arene ligands, exhibited good catalytic performance in the asymmetric transfer hydrogenation (ATH) of various classes of (het)aryl ketones in formic acid/triethylamine mixture. In particular, benzo‐fused cyclic ketones furnished 98 to >99.9% ee using a low catalyst loading.
A new electrocatalytic conversion of alcohols to ketones and aldehydes was developed based on an electrochemical study of Shvo's complex. The oxidation of secondary alcohols was efficiently performed under mild conditions using a catalytic amount of Shvo's catalyst, in combination with a sub‐stoichiometric amount of 2,6‐dimethoxy‐1,4‐benzoquinone in N ,N ‐dimethylformamide at 80 °C. The hydroquinone thus formed is continuously reoxidized with the aid of an electrochemical device. Excellent yields for different ketones, aromatic as well as aliphatic and α,β‐unsaturated ketones, are obtained. In addition, chemoselectivity towards oxidation of the secondary alcohol is achieved when converting vicinal diols such as 1,2‐octanediol and 1,2‐decanediol.
Possibilities for the preparation of substituted ketones by catalytic dehydrogenation of corresponding secondary alcohols were explored using a ZnO–Cr2O3 catalyst at 370–400°C. It was found that addition of about 1 wt% of sodium to the catalyst increases the yield of the ketone because the competitive dehydration of the alcohol is suppressed. Further improvement of the process was achieved by adding 20 wt% of water to the alcohol feed, which inhibited catalyst deactivation. Preparative experiments were conducted and 1-methoxy-2-propanone, 1-methoxy-2-butanone, 1-phenoxy-2-propanone and 2-methoxy-1-cyclohexanone were obtained. 相似文献
A new method was developed to transform alkenes into three types of functional molecules, including epoxides, aldehydes and 1,2‐diols by using dichlororuthenium(IV) meso‐tetrakis(2,6‐dichlorophenyl)porphyrin [Ru(IV)(TDCPP)Cl2] as catalyst and 2,6‐dichloropyridine N‐oxide (Cl2pyNO) as the oxidant, in which the 1,2‐diols were afforded via “one‐pot” reactions in moderate yields. 相似文献
This paper reports the structural modification of Hoveyda–Grubbs complexes through the introduction of either an N‐alkyl‐N′‐mesityl heterocyclic carbene, an N‐alkyl‐N′‐(2,6‐diisopropylphenyl) heterocyclic carbene, or an N‐alkyl‐N′‐alkyl heterocyclic carbene. The effect of the modified N‐heterocyclic carbene (NHC) ligand was investigated in representative ring‐opening metathesis polymerization (ROMP), ring‐closing metathesis (RCM) and cross metathesis (CM) reactions. A pronounced influence on both catalyst activity and selectivity was found to be exerted by the NHC amino substituents, which emphasizes that a rigorously selected steric environment is critical in olefin metathesis catalyst design. 相似文献
A (hydroxycyclopentadienyl)iron dicarbonyl hydride catalyzes the Oppenauer‐type oxidation of alcohols with acetone as the hydrogen acceptor. Many functional groups are tolerant to the oxidation conditions. The same complex also catalyzes the dehydrogenation of diols to lactones. A mechanism involving the formation of iron‐alcohol complexes and their rapid ligand exchange with free alcohols is proposed. The trimethylsilyl groups on the cyclopentadienyl ligand of the catalyst play a critical role in stabilizing the iron hydride and increasing the catalyst lifetime. 相似文献
The copper‐catalyzed intramolecular diastereoselective trifluoromethylcycloetherification of homoallylic alcohols with Togni’s reagent as trifluoromethylating reagent was realized under mild conditions. Various trifluoromethylated tetrahydrofurans were synthesized in moderate to good yields. Moreover, a wide range of common functional groups was tolerated.
