常温常压下吡咯及其衍生物的镍催化加氢反应考察

为进一步研究常温常压下吡咯及其衍生物的镍催化加氢反应,我们对试剂吡咯、吡咯烷和吡咯烷酮做了相应的催化加氢实验。并采用电镜（TEM-HREM）、X射线衍射（XRD）对Ni基催化剂的形貌、结构、加氢活性和超声波对其影响进行了检测,同时还用紫外吸收光谱、气相色谱等对加氢产物进行了分析考察。结果表明超声波能促进镍基催化剂活性,使镍微晶(111)晶面间距增大1.5%、并保持高分散态。常温常压下纳米镍基催化剂对吡咯、吡咯烷和吡咯烷酮的加氢反应显示一定的催化活性;吡咯加氢首先生成吡咯烷,进而使环打开生成低碳烃、氨等产物,总反应为零级,符合表面接触反应特征。     

Catalytic asymmetric hydrogenation of 2,3,5-trisubstituted pyrroles

Catalytic asymmetric hydrogenation of N-Boc-protected pyrroles proceeded with high enantioselectivity by using a ruthenium catalyst modified with a trans-chelating chiral bisphosphine PhTRAP. The ruthenium catalyst prepared from Ru(eta3-methallyl)2(cod) and (S,S)-(R,R)-PhTRAP in the presence of triethylamine was the most enantioselective for the asymmetric hydrogenation of methyl pyrrole-2-carboxylate, giving the desired (S)-proline derivative with 79% ee in 92% yield. Moreover, 2,3,5-trisubstituted pyrroles bearing a large substituent at the 5-position were hydrogenated with 93-99.7% ee. The asymmetric reduction of 4,5-dimethylpyrrole-2-carboxylate gave only all-cis isomer and created three chiral centers with high degree of stereocontrol in a single process. This is the first highly enantioselective reduction of pyrroles.     

常温常压下五元杂环的催化加氢反应

 考察了常温常压下吡咯、呋喃和噻吩的催化加氢反应;用紫外吸收光谱、气相色谱和酸碱度测定分析了反应物质;用比表面积测定、X射线衍射、透射电镜及高分辨电镜表征了催化剂．结果表明,在纳米量级的镍基催化剂作用下,双键五元杂环的加氢反应过程是多反应同时进行：主要有环上双键先加氢生成四氢化物单键环,继而开环加氢生成若干小分子气体;也有直接开环反应．总体上是在还原条件下实现降解反应．超声波的介入有利于保持催化剂的活性．对反应机理进行了探讨．     

Synthesis of nitro and amino N-heterocycles via ring transformation of 2-methyl-3-nitrochromone

2-Methyl-3-nitrochromone ( 1 ) reacted with acid hydrazides, S-methylisothiourea, hydroxylamine and ethyl aminoethanoate to give the nitro derivatives of pyrazole 2 , pyrimidine 6 , isoxazole 11 and pyrrole 13 , respectively. These nitro compounds were reduced by catalytic hydrogenation to the corresponding amino derivatives. In the case of 2 , a rearrangement of the acyl group took place during the reduction. Substitution reactions of the 2-methylthio group in 6 were also described.     

Synthesis of 2,3,3a,8a-tetrahydroindeno[2,1-b]pyrrole derivatives

A new entry into the 2,3,3a,8a-tetrahydroindeno[2,1-b]pyrrole system, 1 , has been investigated. 2,3,3a,8a-Tetrahydro-3a,8a-dihydroxy-1-methylindeno[2,1–6]pyrrole-2,8-dione, 3 , formed from the reaction of ninhydrin and N-methylacetamide has been subjected to catalytic hydrogenation, hydride reduction, and chlorination reactions to afford a variety of substituted derivatives of 1 .     

Hydrogenation of compounds containing an indolizine moiety and of 1-benzylisoquinoline over rhenium heptasulfide

It was shown by hydrogenation of 2,8-diphenylindolizine, benzo[2,3]indolizine, dibenzo[2,3;5,6]indolizine, dibenzo[ 2,3;7,8 ]indolizine, 1-benzylisoquinoline, and 2,3-dimethyl-6-ethyl-4-(4-nitrophenyl)pyridine over Re₂S₇ (250°C, = 140 atm, 4 h) that the pyridine ring in benzoindolizines is hydrolyzed in preference to the pyrrole ring. Phenyl substituents at the indolizine do not prevent its complete reduction while alkyl substituents make reduction difficult. Annelation of the pyrrole and pyridine rings of indolizine lower the degree of its reduction; a nitro group is reduced to an amino group.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1413–1416, June, 1991.     

Liquid phase hydrogenation of some heterocyclic nitrogen compounds over ruthenium catalysts

Results are given for the hydrogenation of some heterocyclic nitrogen compounds (pyrrole, pyridine, indole, quinoline, and acridine) and certain derivatives of them in the liquid phase under pressure, in the presence of ruthenium catalysts. The results obtained indicate that these catalysts are very effective, making it possible to obtain high yields of the corresponding saturated compounds. In the cases of quinoline and acridine, depending on the temperature, double bonds in the polycyclic systems can be selectively hydrogenated.     

New synthesis of condensed heterocycles from isoxazole derivatives VI. 2,5-Dimethyl-3-aeetyl-7-amino-1H-pyrrolo[3,2-b] pyridine

A new synthesis of pyrrolo[3,2-b] pyridine starting with pyrrole ring is described. The procedure allows the synthesis of 4-azaindoles bearing a sensitive group at C-7. The nitration of 4b with nitric acid and acetic anhydride at ?15° gave 5 . The hydrogenation of 5 led to simultaneous reduction of N-hydroxy and nitro groups and to hydrogenolysis of the isoxazole nucleus, affording an appropriate chain of atoms to building up the pyrrolo[3,2-b] pyridine ring.     

Molecular mechanical devices based on quinone-pyrrole and quinone-indole dyads: a computational study

A set of intramolecularly connected dyads consisting of a quinone unit and a pyrrole or indole moiety have been designed and evaluated in quantum-chemical calculations. It is shown computationally for several systems, depending on the length and attachment points of the interconnecting chains, that a reduction of the quinone to the semiquinone radical anion or quinolate dianion state leads to a reversible intramolecular reorientation from a pi-stacked to a T-stacked arrangement. In the rearranged structures, a hydrogen bond from the pyrrole or indole N-H function to the semiquinone or quinolate pi-system is created upon reduction. In some systems, hydrogen bonds to the semiquinone or quinolate oxygen atoms are partly feasible and will be preferred over T-stacking. The choice of systems has been based on recent computational observations related to photosystem I. Systems with pyrrole or indole units should provide a better basis for the envisioned molecular motor than recently proposed quinone-benzene dyads. The intramolecular interactions modify the quinone redox potentials. Electronic g-tensors have been computed for the semiquinone states. These reflect characteristically the presence and nature of hydrogen bonds to the semiquinone and represent suitable electron paramagnetic resonance spectroscopic probes for the preferred structures. Intramolecular proton transfer is possible in the dianionic state.     

Catalytic Hydrogenation of meso‐Octamethylporphyrinogen (Calix[4]pyrrole)

Hydrogenation of meso‐octamethylporphyrinogen (calix[4]pyrrole) with a number of heterogeneous catalysts under different experimental conditions has been investigated. GC‐MS analyses of the reaction mixtures showed the formation of one to four products in low to moderate yields: three of them were diastereoisomers of the product derived from half‐hydrogenation of the substrate, and displayed alternating pyrrolidine and pyrrole rings, while the fourth was the all‐cis saturated product. An acidic medium was necessary to achieve hydrogenation. However, the use of too strongly acidic solvents or additives was detrimental to the stability of the substrate and/or the catalyst.     

Preparation of pyrrole and pyrrolidine derivatives of pyrimidine. 1‐(2‐pyrimidinyl)pyrrole ‐ an inhibitor of X. phaseoli and X. malvacearum

Pyrrole and pyrrolidine derivatives of pyrimidine were prepared in which the nitrogen atom of the pyrrole or pyrrolidine ring is bonded directly to the 2‐ or 4‐carbon atom of the pyrimidine ring. Pyrrole derivatives were prepared by the dry distillation of an intimate mixture of an aminopyrimidine with mucic acid and by the reaction of a chloropyrimidine with potassium pyrrole. Pyrrolidine derivatives were prepared by the reaction of a chloropyrimidine with pyrrolidine and, in a single instance, by the catalytic hydrogenation of a pyrimidinylpyrrole. At a concentration of 200 mcg/mL, 1‐(2‐pyrimidinyl)pyrrole inhibited two plant pathogenic bacteria — Xanthomanus phaseoli (pathogenic on the bean plant) and Xanthomanus malvacearum (pathogenic on the cotton plant).     

Structure sensitivity of carbon-nitrogen ring opening: impact of platinum particle size from below 1 to 5 nm upon pyrrole hydrogenation product selectivity over monodisperse platinum nanoparticles loaded onto mesoporous silica

Well-defined platinum nanoparticles between 0.8 and 5.0 nm were prepared using dendrimer and polymer capping agents and supported onto mesoporous SBA-15 silica. Using these model catalysts, pyrrole hydrogenation was demonstrated to be structure sensitive because ring opening occurred more easily over larger particles compared to smaller ones. The phenomenon is caused by surface roughness or electronic effects that change with particle size.     

Broader,Greener, and More Efficient: Recent Advances in Asymmetric Transfer Hydrogenation

Asymmetric transfer hydrogenation has become a practically useful tool in reduction chemistry in the last decade or so. This was largely triggered by the seminal work of Noyori and co‐workers in the mid‐1990s and is driven by its complementing chemistry to hydrogenation employing H₂. This Focus Review attempts to present a “holistic” overview on the advances in the area, focusing on the achievements recorded around the last three years. These include more‐efficient and “greener” metal catalysts, catalysts that enable hydrogenation as well as transfer hydrogenation, biomimetic and organocatalysts, and their applications in the reduction of C?O, C?N, and C?C bonds. Also highlighted are efforts in the development of environmentally benign and reusable catalytic systems.     

Rate and Stereoselectivity Changes During Hydrogenation of n-Heterocycles

High diastereoselectivities were obtained in the heterogeneous catalytic hydrogenation of chiral pyrrole and pyridine derivatives with complete conversion, in non-acidic medium. The products of the hydrogenations, secondary and tertiary amines act as catalyst modifiers, increasing the d.e. values in the last period of the reactions.     

Total synthesis of the antitumor active pyrrolo[2,1-a]isoquinoline alkaloid (±)-crispine A

Addition of a propargyl Grignard reagent to 3,4-dihydro-6,7-dimethoxyisoquinoline, silver(I)-promoted oxidative cyclization, and chemoselective hydrogenation of the pyrrole ring provide a simple three-step route to the antitumor active pyrrolo[2,1-a]isoquinoline alkaloid (±)-crispine A.     

Organocatalytic transfer hydrogenation of cyclic enones

The first enantioselective organocatalytic transfer hydrogenation of cyclic enones has been accomplished. The use of iminium catalysis has provided a new organocatalytic strategy for the enantioselective reduction of beta,beta-substituted alpha,beta-unsaturated cycloalkenones, to generate beta-stereogenic cyclic ketones. The use of imidazolidinone 4 as the asymmetric catalyst has been found to mediate the hydrogenation of a large class of enone substrates with tert-butyl Hantzsch ester serving as an inexpensive source of hydrogen. The capacity of catalyst 4 to enable enantioselective transfer hydrogenation of cycloalkenones has been extended to five-, six-, and seven-membered ring systems. The sense of asymmetric induction is in complete accord with the stereochemical model first reported in conjunction with the use of catalyst 4 for enantioselective ketone Diels-Alder reactions.     

Recent topics of transfer hydrogenation

A number of transition metal catalysts have been developed for transfer hydrogenation of organic molecules. This method provides a useful process for the reduction of unsaturated molecules without the need for explosive hydrogen gas. An important development in this area is the design of new ligands that improve activity and selectivity under mild reaction conditions. Polydentate ligands are good candidates for producing high performance metal catalysts. This digest describes recent developments in transfer hydrogenation as well as asymmetric reactions using metal catalysts containing polydentate ligand systems.     

高效钴氧化物催化羧酸可控加氢制醇（英文）

羧酸选择加氢是合成醇的重要方法,廉价高效的催化体系仍然在探索中.我们利用地球上储量丰富的钴氧化物作为催化剂,通过控制催化反应过程,进而实现高选择性地催化羧酸加氢制备醇.一系列含有不同官能团的羧酸可以被选择加氢至相应的醇类化合物,反应选择性可以满足工业生产要求.通过一系列的谱学表征以及理论计算,我们证实了钴氧化物在羧酸选择加氢反应中的优选活性位点位为氧化亚钴,从而建立了催化剂与反应活性之间的构效关系,为催化剂的理性设计提供指导.首先,我们选取硬脂酸加氢反应作为模型反应,通过对地球上储量丰富的氧化镍、四氧化三铁和四氧化三钴的催化活性对比发现,四氧化三钴催化剂活性最高,在473 K,2 MPa氢气条件下,反应速率可以达到1.2 mmol/(h·g).对四氧化三钴催化剂进行不同温度的预还原处理,我们发现催化剂的活性得到显著提高,其中573 K还原的样品活性最高,反应速率可以达到7.3 mmol/(h·g),要远远高于贵金属催化剂Pd/C(0.6 mmol/(h·g))和Pt/C(1.8 mmol/(h·g)).XRD结果表明,随着还原处理温度的不断升高,催化剂由四氧化三钴变为氧化亚钴,最终变为金属态的钴.当还原温度为573 K时,催化剂的组成为单一相氧化亚钴.XPS测试结果表明,当还原温度为573 K时,样品中只含有Co~(2+)的信号峰,并且Co/O的比例为1/1,进一步证明样品是纯态的氧化亚钴.从TEM照片中可以发现,在原始的四氧化三钴样品中观察到晶面间距为0.467和0.244 nm,分别对应四氧化三钴的(111)和(311)晶面.而对于573 K还原的样品只观察到一种晶面间距(0.246 nm),对应氧化亚钴的(111)晶面.结合表征手段和硬脂酸催化加氢活性结果,我们得出氧化亚钴是573 K还原样品催化羧酸加氢反应的活性位点.理论计算结果进一步证实了这个实验结论.理论计算结果表明,在氧化亚钴(111)晶面,硬脂酸加氢转换为十八醇是非常快速和高效的,然而,对于氢解C-C键和C-O键,需要耗费更高的能量,能垒约为1.2 e V.因为硬脂酸的吸附远远强于十八醇的吸附,硬脂酸的存在会抑制十八醇氢解形成烯烃的反应,只有当硬脂酸酸完全转化为十八醇,才会发生随后的氢解反应.通过控制催化反应过程,可以实现在氧化亚钴(111)晶面高选择性催化酸加氢至醇,也就是反应控制催化过程.基于氧化亚钴在硬脂酸加氢制备十八醇上的优异催化性能,我们进一步研究了一系列含有不同官能团的羧酸化合物的催化加氢,发现氧化亚钴表现出良好的官能团容忍度,可以实现高效、广谱的酸选择加氢至醇反应.     

制备溶剂对NiCoB非晶态合金催化剂结构及糠醛加氢性能的影响

采用化学还原法在不同单一和复配溶剂体系中制备了一系列NiCoB非晶态合金催化剂,对其液相糠醛加氢性能进行了考察,并采用N_2吸附-脱附等温线、ICP、FE-SEM、HRTEM、XRD、XPS等手段进行了表征。结果表明,在相同反应条件下,制备溶剂的表面张力、黏度、极性大小和溶解度常数等对NiCoB非晶态合金催化剂的组成、形貌和结构及其糠醛加氢反应性能均产生重要影响。由甲醇/乙二醇复配溶剂(MEG,体积比1∶1)制备的NiCoB-MEG催化剂具有最理想的糠醛液相加氢制糠醇性能,糠醛转化率达到96.4%,糠醇选择性达到83.49%,这可归因于甲醇和乙二醇之间的协同作用促进了金属组分的分散和还原。     

Integrating Biomass into the Organonitrogen Chemical Supply Chain: Production of Pyrrole and d-Proline from Furfural

Production of renewable, high-value N-containing chemicals from lignocellulose will expand product diversity and increase the economic competitiveness of the biorefinery. Herein, we report a single-step conversion of furfural to pyrrole in 75 % yield as a key N-containing building block, achieved via tandem decarbonylation–amination reactions over tailor-designed Pd@S-1 and H-beta zeolite catalytic system. Pyrrole was further transformed into dl -proline in two steps following carboxylation with CO₂ and hydrogenation over Rh/C catalyst. After treating with Escherichia coli, valuable d -proline was obtained in theoretically maximum yield (50 %) bearing 99 % ee. The report here establishes a route bridging commercial commodity feedstock from biomass with high-value organonitrogen chemicals through pyrrole as a hub molecule.