小分子伯胺催化异噁唑有氧还原开环反应(英文)

有机催化是催化领域的前沿.在水介质中,以水合肼作为还原剂研究了小分子有机胺催化3-甲基蒽醌-[1,2-c]-异噁唑有氧还原开环反应高效合成1-氨基-2-乙酰基蒽醌,详细考察了不同种类有机胺对异噁唑有氧还原开环反应的催化性能,发现小分子有机伯胺具有很好的还原开环催化性能.在1倍水合肼存在下室温反应3 h,3-甲基蒽醌-[1,2-c]-异噁唑转化率和目标产物1-氨基-2-乙酰基蒽醌选择性均可达到97.2%.产物的分子结构经氢核磁谱和质谱得以确证.此外,提出了小分子有机伯胺催化3-甲基蒽醌-[1,2-c]-异噁唑有氧还原开环反应合成1-氨基-2-乙酰基蒽醌的可能反应机理.     

1,5-二硝基蒽醌电化学还原制备──1,5-二氨基-4,8-二羟基蒽醌的研究(英文)

采用循环伏安法、稳态极化曲线法和恒电位电解法相结合的实验手段,研究了１,５－二硝基蒽醌（１,５－ＤＮＡ）在硫酸溶液中、汞齐化铜电极上阴极还原制备１,５－二氨基－４,８－二羟基蒽醌（１,５－ＤＡ－４,８－ＤＨＡ）的电化学反应性能．结果表明：在１２．７５ｍｏｌ／ＬＨ２ＳＯ４和１４０℃温度下,１,５－ＤＮＡ在汞齐化铜阴极表面上具有反应物强吸附和不可逆随后化学反应的特征．电解最后的产物经红外光谱测定为１,５－二氨基－４,８－二羟基蒽醌,平均电流效率为７８％,产率为７２％．１,５－ＤＮＡ直接电化学还原的行为与电极材料、酸浓度、添加剂、反应物浓度等有关．     

铜催化异噁唑还原环清洁高效合成1-氨基-2-乙酰基蒽醌简

以水为反应介质,水合肼为还原剂,研究了痕量铜催化3-甲基蒽醌-[1,2-c]-异噁唑还原开环反应以清洁高效合成1-氨基-2-乙酰基蒽醌,考察了不同种类过渡金属硝酸盐的催化性能,发现Cu（NO₃）₂性能最好. 加入 2.6% 的催化剂和1.3倍的水合肼,在室温反应 2 h,底物转化率和目标产物选择性分别可达到 97.2%和 95%,TON达到38. 产品结构经氢核磁谱和质谱得以确证,主要副产为羟基取代的1-氨基-2-乙酰基蒽醌. 此外,提出了铜催化 3-甲基蒽醌-[1,2-c]-异噁唑还原开环反应合成 1-氨基-2-乙酰基蒽醌的可能反应机理.     

蒽醌法生产过氧化氢用新型氢化催化剂的制备

 采用水合肼液相还原法制备了负载型镍催化剂，对其催化蒽醌加氢反应的活性进行了考察，采用电感耦合等离子发射光谱、X射线衍射以及H2化学吸附等手段对催化剂进行了表征，并与用氢气还原法制备的催化剂进行了对比．结果表明，用水合肼还原制备的催化剂的Ni粒子较大，Ni分散度及H2吸附量较低，但其催化蒽醌氢化反应的活性高得多．     

应用固定化Baker's酵母还原醌类化合物的研究

苯醌、萘醌和蒽醌类化合物在水溶液中能被固定化Baker's酵母还原。本文研究了影响固定化Baker's酵母还原活性、醌类化合物还原速度的因素及还原产物的分离和稳定性。     

蒽醌/聚吡咯复合膜修饰电极的电化学行为和电催化活性

在水溶液中制备了掺杂蒽醌磺酸盐(AQS)的聚吡咯(PPy)/玻碳复合膜修饰电极,采用循环伏安法和旋转圆盘电极技术研究了该修饰电极在不同pH值溶液中的电化学行为以及在pH=5.5的磷酸盐缓冲溶液中对氧还原反应的电催化性能和动力学.结果表明,与裸玻碳电极相比,PPy膜的存在不仅降低了AQS的反应电位和峰电位差,而且增大了其氧化还原反应的峰电流,H2AQ/HAQ-氧化还原对的电离常数为9.5.AQS/PPy膜修饰电极上氧的还原主要是两电子还原为H2O2的不可逆过程,H2AQ对氧还原反应起主要催化作用,还原过程符合异相氧化还原催化机理.该修饰电极具有良好的电化学重现性.     

蒽醌类染料的电化学行为研究

采用玻碳电极研究了蒽醌类染料的电化学行为.研究发现,由活性艳蓝KN-R表现出的伏安特性可推断出负电位区发生的是蒽醌基和氢醌基的互变反应,正电位区发生的是氨基的氧化反应.由分散红3B的伏安图可推断出在负电位区发生的是蒽醌基的还原,在正电位区存在氨基和羟基的氧化还原反应.而分散蓝2BLN的伏安图能推断出负电位区的蒽醌基的还原反应,但正电位区只能观察到一个氧化峰.     

米托蒽醌在金电极上的电化学研究及其应用

米托蒽醌(MTX)在0.2 mol/L B-R缓冲溶液(pH=1.5)中循环伏安扫描时,在金电极上会产生一个灵敏的氧化峰P1(峰电位为1.087 V)和两个灵敏的还原峰P2(峰电位为0.817 V)、P3(峰电位为0.764 V)。P1峰电流值与MTX浓度在1.0×10-9~1.0×10-6mol/L范围内呈良好的线性关系;其检出限可达5.6×10-10mol/L。本研究优化了测定米托蒽醌的最佳实验条件,建立了可灵敏测定米托蒽醌的新方法;同时对米托蒽醌在金电极上的电化学行为进行了较为详细的研究。     

米托蒽醌在离子注入修饰电极上的伏安行为及其应用

在0.1mol/LNH₃-NH₄Cl缓冲溶液(pH_9.5)中,米托蒽醌在镍离子注入修饰电极上有一灵敏的伏安还原峰,峰电位为-0.85V(vs.SCE).峰电流与米托蒽醌的浓度成线性关系.检出限为1.8×10^-8mol/L.研究了其伏安行为,并将该波用于尿样的测定.结果表明,还原过程为具有吸附性和催化性的准可逆过程.AES和XPS实验表明,Ni已注入到玻碳电极的表面,使电催化活性提高.     

1,2,1′,2′-双蒽醌-3,12-二羧酸的还原反应

1,2,1＇,2＇-双蒽醌-3,12-二羧酸(1)是一个π-共轭体系芳环化合物,内环酮基由于受空间效应和共振效应的影响,不能被还原成相应的醇或相应的碳氢基团,却成了不常见的内“双氧桥”化合物(4)。化合物2,3,4的结构已经确定,并对1的还原机理进行了初步讨论。     

New -lactam systems from penicillins

3-Isopropyl-4-thia-2,6-diazabicyclo[3.2.0]heptan-7-on ( 8 ), a potential intermediate for the synthesis of new β-lactam antibiotics [5], was prepared from the urethanes 7a and 9 by reduction with zinc/acetic acid. The cyclic Schiff base 10 , which constitutes an intermediate in this reaction, was prepared by reduction of 9 with CrCl² and was further reduced to 8 with zinc/acetic acid.     

Synthesis of 3,4-Dihydrophthalazin-1(2H)-one by Zinc Reduction of Phthalazin-1(2H)-one

3,4-Dihydrophthalazin-1(2H)-one (II) was first prepared by H.Sund ¹⁾, by electrochemical reduction of phthalazin-1(2H)-one (I) (phthalazone). In the recent years we have described new syntheses of II, through easily hydrolyzable mono- or diacetyl- derivatives, namely condensation of 2-bromomethylbenzoylchloride with N,N'-diacetylhydrazine ²⁾ catalytic reduction of I in acetic acid ²⁾ or of 2-acetylphthalazone in acetic anhydride ³⁾ The reduction of I with zinc is known to proceed with ring contraction and formation of N-aminophthalimidine (III)⁴⁾ (zinc and sodium hydroxide at about 100[ddot]C) or of phthalimidine (IV) ⁵⁾ (zinc and hydrochloric acid under unspecified conditions).

Having observed that II is transformed into N-aminophthalimidine when heated with hydrazine hydrate ⁶⁾ or sodium hydroxide ²⁾, the zinc reduction of I was reinvestigated with the aim to find out in which cases the intermediate formation of II can be dem-onstratedo     

Reduction of the 1,2,5-thiadiazole ring of 3,6:12,15-di-1,4-benzo[6.6](3,4)-1,2,5-thiadiazolo- and 3,5:11,13-di-1,3-benzo-[6.6](3,4)-1,2,5-thiadiazolocyclophanes. Selective preparation of cis- and trans-[23]cyclophane-1,2-diacetoamide

The effect of the [2.2.2]cyclophane ring structure on the reduction of 1,2,5-thiadiazole ring incorporated in cyclophanes 1a-c and 2a-c was investigated. When reduced by sodium metal in ethanol followed by acetylation, para[2³]cyclophane 1 gave a mixture of the expected cis- and trans-diamides, 3 and 4 , in which 4 was the major product. On the other hand, reduction of 1 with lithium aluminum hydride proceeded in a cis-selective manner and gave 3 as a major product after a treatment of the reduced products with acetic anhydride. The reduction of metacyclophane 2 , which is less strained than 1 , proceeded exclusively in cis-fashion and a subsequent treatment of the reduction product with acetic anhydride gave only cis-diamide 6 .     

Rearrangement of the benzidine type in the indole series

12-Acetamidoindolo[1,2-c]quinazolities were obtained by treatment of 3-arylazoindoles with zinc in acetic acid in the presence of acetic anhydride and sodium acetate. The products were converted to the corresponding amines by hydrolysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1096–1098, August, 1975     

Different specificities in the bromination of 6-(2-furyl)imidazo[2,1-b]thiazole and its derivatives with 1 mole of bromine

The action of 1 mole of bromine on 6-(2′-furyl)imidazo[2,1-b]thiazole, its 2-methyl-, 3-methyl-, and 2,3-dimethyl-substituted derivatives, and their hydrobromides in chloroform and glacial acetic acid was studied. The bromination of bases containing a methyl group in the 3 position leads primarily to the 5′-derivatives with respect to the furan ring in chloroform, whereas in the remaining cases 5-bromo derivatives with respect to the imidazothiazole system are formed. Compounds of the latter type are formed by the action of bromine in glacial acetic acid or of sodium hypobromite in alkaline media on the bases. The hydrobromides are brominated in both acetic acid and chloroform, regardless of the substituents in the thiazole ring, primarily in the 5′ position of the furan ring. The structures of the bromination products were proved by means of alternative syntheses, thin-layer chromatography, and the PMR spectra.     

Synthesis and Complexing Properties of Alkyl (3-Oxo-2,3-dihydrothiophen-2-ylidene)- and (4-Oxothiazolidin-5-ylidene)acetate Derivatives

Condensation of dimethyl and diethyl acetylenedicarboxylate with thioacetamides gave the corresponding alkyl (3-oxo-2,3-dihydrothiophen-2-ylidene)- and (4-oxothiazolidin-5-ylidene)acetates. Treatment of these compounds with zinc in acetic acid resulted in reduction of the exocyclic double bonds. The products can be used in membrane processes as sodium cation carriers.     

Furopyridines. I. Synthesis of furo[2,3-c]pyridine

The parent framework of furo[2,3-c]pyridine has been synthesized. 3-Furoic acid chloride ( 2 ) was reduced with bis(triphenylphosphine) copper(1) tetrahydroborate to afford 3-furaldehyde ( 3 ) which was condensed with malonic acid to give β-(3-furyl)acrylic acid ( 4 ). The acrylic acid 4 was converted to the acid azide ( 5 ), which in turn was cyclized to give furo[2,3-c]pyridin-7(6H)-one ( 6 ) by heating at 180° in diphenylmethane. The pyridone 6 was chlorinated with phosphorus oxychloride, followed by reduction with zinc and acetic acid to give furo[2,3-c]pyridine ( 8 ).     

Convenient preparation of O-linked polymer-bound N-substituted hydroxylamines, intermediates for synthesis of N-substituted hydroxamic acids

[reaction: see text] An efficient procedure for preparation of O-linked polymer-bound N-substituted hydroxylamines by reduction of resin-bound oximes with borane.pyridine complex in the presence of dichloroacetic acid is reported. Other reducing systems commonly used for imine or oxime reduction were ineffective, including borane.pyridine in the presence of acetic acid. Oximes derived from a variety of aromatic and aliphatic aldehydes and ketones were successfully reduced. The N-substituted products were acylated and cleaved from resin to afford N-substituted hydroxamic acids.     

Reductive cleavage and subsequent transformations of 5-oxa-6-azaspiro[2.4]heptane-1-carboxylates

Treatment of methyl 4,6-diaryl-5-oxa-6-azaspiro[2.4]heptane-1-carboxylates with zinc in acetic acid leads to cleavage of the N–O bond in the isoxazolidine ring with formation of 1,3-amino alcohols whose subsequent cyclization under the reaction conditions yields bi- or tricyclic lactams or lactones with retention of the three-membered ring.     

Synthesis of 3a,4,6,7,11b,12-hexahydro-3a-methyl-7-phenylbenzo[a]furo[2,3-g]quinolizines

By alkylation of stereoisomeric 7a-methyl-2-oxo-5-phenylfuro-[2,3-c]piperidines with phenacyl bromide and subsequent reduction of the keto group by sodium borohydride, amino alcohols were obtained; heating of these products in 70% sulfuric acid affords 3a,4,6,7,11b,12-hexahydro-3a-methyl-7-phenylbenzo[a]furo[2,3-g]quinolizines. It was found that the cis-quinolizidine, upon heating to 150°C in acetic acid, is isomerized to the trans-quinolizidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1679–1682, December, 1993.