Selective deoxygenation of styrene oxides under a CO atmosphere using silver nanoparticle catalyst

Deoxygenation of styrene oxide derivatives into the corresponding alkenes was efficiently catalyzed by inorganic materials of hydrotalcite-supported silver nanoparticles (Ag/HT) using CO/H₂O as a reductant. The Ag/HT catalyst was reusable without loss of activity or selectivity.     

The catalytic hydrogenolysis of benzylamine derivatives

The hydrogenolysis of optically active ethyl 2-amino-2-phenylpropionate (I), its N-methyl (II), and N,N-dimethyl (III) derivatives was studied using Raney Ni and Pd as the catalysts. The Raney Ni catalysed hydrogenolysis of II and III, as well as the reaction catalysed by Pd, occurred predominantly with inversion of configuration; this is not in accord with the hydrogenolysis of corresponding benzyl alcohols. This difference can be ascribed to the difference of the affinity for Ni between N and O atoms. The “SN_Ni” process may be inhibited in the Raney Ni catalysed hydrogenolysis of II and III since the amino group acts as a self-catalyst poison, and the “S_N2” process appears to be preferable to the “S_Ni” one. The predominance of the configurationally inversion was also observed in the Pd catalysed hydrogenolysis of I. These results over Pd are reasonable in reflecting that the N atom has not so high affinity for Pd. The hydrogenolysis of a quarternary ammonium bromide of I was also reported.     

Stereochemistry modulates the catalytic hydrogenolysis of nitrile-substituted cyclopropanes

The study of Raney-Ni catalyzed chemo- and regioselective hydrogenolysis of diastereomeric nitrile-substituted spirocyclopropyloxindoles is presented. The chemoselectivity outcome of the reaction is remarkably influenced by the relative stereochemistry of the nitrile-substituted spirocyclopropyloxindoles. Chemo- and high regioselective cyclopropane ring-opening occurs from the syn diastereomers to give the corresponding 3-propylacetamide derivatives. X-ray crystallographic studies together with DFT model chemistry calculations indicate that chemo- and regioselectivity are directly dependent on the bond length asymmetry of the cyclopropane ring.     

Deoxygenations of arene oxides. Models for enzymatic deoxygenation

The transfer of oxygen from arene oxides to nitrogen and sulfur-containing substrates is described and the possible biological Significance relative to enzymatic deoxygenation discussed.     

The catalytic system tri-n-butyl boron-p-quinone in the free-radical polymerization of styrene

The AIBN-initiated polymerization of styrene is conducted at 60 and 80°C in the presence of tri-n-butyl boron and several p-quinones. The rate of polymerization and the molecular-mass characteristics of the polymers depend on the structure of the used p-quinone and the temperature of the process.     

Porous Pd-containing polypropylene membranes for catalytic water deoxygenation

Water deoxygenation has been studied in a catalytic membrane reactor in which oxygen is reduced with hydrogen fed into the hollow fiber of a porous polypropylene membrane containing palladium metal on its outer surface. Palladized fibers obtained by different methods and the initial fibers have been characterized by dynamic desorption porosimetry, gas permeability measurements, X-ray structure determination, and light microscopy. The possibility of efficient water deoxygenation at room temperature is demonstrated.     

HCl/DMF for enhanced chemoselectivity in catalytic hydrogenolysis reactions

An improved, chemoselective hydrogenolysis method has been developed. By employing a solvent-acid combination (i.e., DMF-aq HCl) we were able to favor debenzylation rather than aromatic hydrogenation and acid-mediated bond cleavage which are the two main drawbacks of these reactions. The generality of the method, which was primarily developed as a solution to a carbohydrate problem, is shown by the successful hydrogenolysis of 1,8-naphthalide, a previously unsolved problem.     

The catalytic hydrogenolysis of 1-phenylbicyclo[4.1.0]heptane and the corresponding azidirine and epoxide

The hydrogenolysisof 1-phenylbicyclo[4.1.0]heptane (1a), cis-1-phenyl-2-methylbicyclo[4.1.0]heptane (1b), 1-phenyl-7-azabicyclo[4.1.0]heptane (2) and 1-phenyl-7-oxabicyclo[4.1.0]heptane (3) was studied using Ni, Pd, Rh and Pt as catalysts. The hydrogenolysis of the C₁C₇ bond of 1a and 1b led to the selective formation of trans-1-phenyl-2-methylcyclohexane (4a) with retention of configuration. Compound 1a gave not only 4a but also phenylcycloheptane (6a), which is the product of C₁C₆ bond fission, and the ratio of 6a to 4a increased in the sequence: Ni ? Pd, Rh < Pt. No C₁C₆ bond fission was observed in the hydrogenolysis of 1b. These results can be explained by a mechanism involving the formation of the π-benzyl complex.trans-2-Phenylcyclohexylamine (8) was obtained stereoselectively in the hydrogenolysis of 2 over Raney Ni. This selective formation can be ascribed to the competition of “SN i” and “radical” processes. The Pd catalysed hydrogenolysis gave cis-2-phenylcyclohexylamine (9) as the main product, while the presence of sodium hydroxide promoted the formation of 8.Raney Ni catalysed hydrogenolysis of 3 yielded a mixture of phenylcyclohexane (13) and 2-phenylcyclohexanols (10 and 11). trans-2-Phenylcyclohexanol (10) was the dominant isomer; the hydrogenolysis resulted in the predominant configurational retention. Compound 13 was confirmed to be produced via 1-phenylcyclohexene (12). This deoxygenation may be explained by a mechanism involving the radical cleavage reaction of 3. The presence of sodium hydroxide led to the formation of cis-2-phenylcyclohexanol (11). The Pd catalysed hydrogenolysis also gave mainly 11.The difference in behaviour of cyclopropane, azidirine and epoxide we ascribe to the differences in the affinity for the catalyst and differences in the electronegativity between C, N and O atoms.     

过渡金属氧化物掺杂对铜锰氧化物催化CO氧化性能的影响

以乙酸铜和乙酸锰为铜锰前驱体,以NH₄HCO₃为沉淀剂,相应金属硝酸盐为掺杂剂,采用共沉淀法制备了不同过渡金属氧化物掺杂的铜锰氧化物催化剂.?采用N₂物理吸附、X射线衍射,氢气-程序升温还原和原位红外漫反射光谱等方法对催化剂进行了表征,考察了系列催化剂上CO反应性能.?结果表明,掺杂过渡金属氧化物可以调变催化剂对CO的吸附能力,进而影响催化剂性能.     

Artificial intelligence pathway search to resolve catalytic glycerol hydrogenolysis selectivity

The complex interaction between molecules and catalyst surfaces leads to great difficulties in understanding and predicting the activity and selectivity in heterogeneous catalysis. Here we develop an end-to-end artificial intelligence framework for the activity prediction of heterogeneous catalytic systems (AI-Cat method), which takes simple inputs from names of molecules and metal catalysts and outputs the reaction energy profile from the input molecule to low energy pathway products. The AI-Cat method combines two neural network models, one for predicting reaction patterns and the other for providing the reaction barrier and energy, with a Monte Carlo tree search to resolve the low energy pathways in a reaction network. We then apply AI-Cat to resolve the reaction network of glycerol hydrogenolysis on Cu surfaces, which is a typical selective C–O bond activation system and of key significance for biomass-derived polyol utilization. We show that glycerol hydrogenolysis features a huge reaction network of relevant candidates, containing 420 reaction intermediates and 2467 elementary reactions. Among them, the surface-mediated enol–keto tautomeric resonance is a key step to facilitate the primary C–OH bond breaking and thus selects 1,2-propanediol as the major product on Cu catalysts. 1,3-Propanediol can only be produced under strong acidic conditions and high surface H coverage by following a hydrogenation–dehydration pathway. AI-Cat further discovers six low-energy reaction patterns for C–O bond activation on metals that is of general significance to polyol catalysis. Our results demonstrate that the reaction prediction for complex heterogeneous catalysis is now feasible with AI-based atomic simulation and a Monte Carlo tree search.

An end-to-end artificial intelligence framework for the activity prediction of heterogeneous catalytic systems (AI-Cat method) is developed and applied for resolving the selectivity of glycerol hydrogenolysis on Cu catalysts.     

Synthesis of 2,5-dialkylpyrrolidines by conjugated catalytic hydrogenolysis of furan amines

Conclusions In hydrogenation in the vapor phase on a skeletal nickel-aluminum catalyst at 210–220°, 1-furyl-3-aminoalkanes undergo conjugated hydrogenolysis of the furan series at the 1,5-, 1,5- and 4,5-, as well as 1,5- and 3,4-bonds, forming 2-methyl-, 2-ethyl-, and 2-n-propyl-5-alkylpyrrolidines in yields of 38, 19, and 43%, respectively.Translated from Izvestiya Akademii Nauk SSSR, Setiya Khimicheskaya, No. 6, pp. 1120–1123, June, 1964     

甲酸为氢源的甘油催化选择氢解

以甲酸作为氢源, 采用铜基复合金属氧化物催化剂, 催化氢解甘油制备1,2-丙二醇, 其中液相甲酸的高选择性分解是实现甘油氢解的必要和关键步骤. 活性测试表明, 高分散的铜和ZrO₂载体间的协同作用对甲酸分解和甘油到1,2-丙二醇的转化至关重要, 20%Cu/ZrO₂催化剂的活性最佳. 由于避免使用相对昂贵的化石燃料氢, 因而该催化体系在生物质的高值利用方面具有潜在的应用前景.     

Consequences of affinity in heterogeneous catalytic reactions: highly chemoselective hydrogenolysis of iodoarenes

The catalytic hydrodeiodination reaction using molecular hydrogen and Pd/C has been revisited. It is shown, for the first time, that the chemoselectivity of this reaction is controlled by the high affinity of the iodinated compound for the catalyst. This reaction is compatible with most easily reducible functional groups (nitro, aldehyde, olefin, etc.). Using this reaction, the first general method for tritium labeling of 3-(trifluoromethyl)-3-phenyldiazirine is described.     

Stereoselective synthesis of styrene oxides via a Mitsunobu cyclodehydration

[reaction: see text] The Mitsunobu cyclodehydration of chiral phenethane-1,2-diols (4), readily accessed from the styrene derivative (5), has been demonstrated to provide the corresponding styrene oxides (2) with high levels of stereoretention (up to 99%). Optimized reaction conditions are described, from which the combination of tricyclohexylphosphine (Chx(3)P) and diisopropylazodicarboxylate (DIAD) in THF and R = EWG provides the best results.     

气相色谱法同时测定苯乙烯催化氧化反应液中的苯乙烯、环氧苯乙烷和苯甲醛

建立了同时测定苯乙烯催化氧化反应液中的苯乙烯、环氧苯乙烷和苯甲醛的气相色谱分析方法。该法以正庚烷为内标物,在DB-1毛细管色谱柱上进行分离,氢火焰离子化检测器。方法的回收率98%~101.5%,相对标准偏差小于2.0%。