Mono-Allylation of Gem-Diacetates with Allylsamarium Bromide

Our group have explored the reaction of allylsamarium bromide with a variety of substrates, such as N-(2-aminoalkyl)benzotriazoles1, imines2, nitriles3, diorgano diselenides4, disulfides5, isocyanates6 and nitroalkenes7. Here we wish to report the monoallylation of gem-diacetates with allylsamarium bromide. Gem-diacetates are stable in neutral and basic media, thus they are frequently used to protect aldehydes8. However, the presence of two leaving groups at the same carbon may make carbon …     

Synthesis and Crystal Structure of 1,2,4,6-Tetraphenyl-2-hydroxy-8-azabicycle[3,2,1]octane

1 INTRODUCTIONAtrope alkaloids, which exist in eggplant plants, such as atrope and scopolamine, are used as a series of important drugs in medical science [1,2]. The typical character of atrope alkaloid is that these compounds contain the main skeleton of 8-azabicycle[3,2,1]octane , which results in the very complicated synthetic routine[3]. During our research for the reaction of 1,3,5,7-tetraphenyl-4- nitro-1,7-heptadione with low-valent titanium reagent, we easily synthesized the title …     

Two New Compounds from Goniothalamus Cheliensis Hu

Goniothalamus cheliensis Hu (Annonaceace) is a small tree or shrub in Yunnan Province, southwest of China. Acetogenins, styryllactones and alkaloids1-3 from the genus were reported in the previous literature and many of them showed strong cytotoxic activities against a number of human cancer cell lines4. The titled plant has been the subject of our investigation due to the impressive cytotoxicity of its organic extract against mouse lymphocytic leukemia cells in preliminary pharmacological s…     

CoMn@NC催化5-羟甲基糠醛常压氧化为2, 5-呋喃二甲酸二甲酯

2, 5-呋喃二甲酸二甲酯(DMFDCA)这一生物质衍生的增值化学品是石油基聚合物单体对苯二甲酸(TPA)的理想替代品。本研究采用一步共热解法合成了两种廉价金属修饰的氮掺杂多孔碳催化剂CoMn@NC,并将其用于5-羟甲基糠醛(HMF)在温和条件下的需氧氧化。由Co₃Mn₂@NC-800催化HMF在50 ℃和常压氧气的条件下反应12 h后,得到产率为85%的DMFDCA。多孔催化剂的高比表面积提高了传质效率。Co纳米粒子(NPs)和呈原子级分散的Mn与掺杂在碳中的氮配位形成M―N_x。富含吡啶氮的碳基体中的缺电子金属位点有利于HMF和氧的活化。氧形成的超氧自由基阴离子的存在确保了半缩醛中间体和5-(羟基甲基)-2-糠酸甲酯(HMMF)的羟甲基的脱氢氧化,从而高选择性得到DMFDCA。该催化剂性能稳定,可适用于各种取代芳醇。该催化体系具有用于生产聚合物单体羧基酯的应用潜力。     

糠醛氧化合成糠酸

糠酸作为糠醛的重要下游产品,在食品制造、材料制备、光学技术、药物合成中具有重要的应用,可用于合成防腐剂、增塑剂、热固性树脂、香料以及多种药物。目前,关于糠醛的制备以及催化氢化制备下游产物的综述报道相对较多,但是还没有系统地整理评述糠醛氧化合成糠酸的相关工作。本文综述了近年来以糠醛为主要原料制备糠酸的研究进展情况,讨论了不同催化体系及在不同氧源存在下对糠酸选择性的影响,重点突出了非均相催化剂在糠酸的工业化制备中的应用前景,对糠酸制备的未来发展方向进行了展望。     

Synthesis and Structure of E-2-(2,4,6-tri tert butylphenylphosphinyl)-2-〔N-(tert-butyldimethylsilyl)-N-(p-chrolophenyl)〕amino-1-(2,4,6-tri tert-butyl-phenyl)phosphacthylene

1　INTRODUCTIONItwaswellknown thatelementsofthesecondary and higherrow are in generaldifficulty to form multiplebondsin which apπ hybridized stateisinvolved〔1〕.Thus,simple compounds containing multiple phosphorus carbon bonds,such as methyl dynephosphine( HC≡P) 〔2 - 3〕 and methylenephosphine( H2 C=PH〔4〕,are notstableat room temperature.Three methods to stabilize compounds containing double ormultiple bond involving phosphorusatom in the pπ hybridized state are often used.The f…     

Site-specifically Hydrolytic Cleavage of Oxidized Insulin B Chain With Cu(II) Ion

Selectively chemical cleavage of peptides and proteins is one of the most important reactions in both chemical and biochemical processes. Over the past decade, the interaction of palladium(II) complexes with methionine, cysteine and histidine-containing peptides and proteins and the hydrolytic cleavage of the corresponding amide bond by Pd(II) complexes have been extensively studied1-13. However, reports concerning the directly selective hydrolysis of peptides and proteins with other simple …     

A New ent-Kaurane Diterpenoid from Isodon enanderianus

Isodon enanderianus (Hand. -Mazz.) H. W. Li, has been used in folk medicine as anti-inflammatory and detoxified agent1. The Isodon genus is known to be rich in ent-kaurane diterpenoids, a series of new ent-kaurane diterpenoids have been isolated from the dried leaves of I. enanderianus2-4. In order to find more biologically active substances, we have carefully investigated the chemical constituents of I. enanderianus collected in Shiping county of Yunnan province, and as a result, enanderi…     

Photochemical Reduction of Aromatic Imines by 2-Phenyl-N, N-dimethylbenzimidazoline

Reduction of C=N double bonds has been recognized as an important reaction both in organic chemistry and bio-chemistry1. Hantzsch 1,4-dihydropyridine (HEH, one of NADH model compounds) has been reported as a reductive reagent for imines2. However, application of dihydropyridines as practical reducing reagents in organic synthesis is limited because of their instability3. Like NADH models, 2-phenyl-N, N-dimethylbenzimidazoline (PDMBI) is an efficient electron and hydrogen donor (Eox = 0…     

Retention Behaviors of Uronic Acid-containing Polysaccharides and Neutral Polysaccharides in HPGPC

The determination of molecular weights (Mw) of polysaccharides has served as an important process since the physical properties of the polysaccharides are closely related to their Mw and/or molecular weights distribution (MWD). For Mw and MWD determinations, high performance gel permeation chromatography (HPGPC) has gained wide acceptance as a preferred method due to its high sensitivity, speed and reproducibility. In chromatography, it is well known that the molecular weights are determ…