Ketones to amides via a formal Beckmann rearrangement in ‘one pot’: a solvent-free reaction promoted by anhydrous oxalic acid. Possible analogy with the Schmidt reaction

A variety of ketones can be directly converted into the secondary amides expected from a Beckmann rearrangement of the corresponding oximes in high yield, by heating them with hydroxylamine hydrochloride and anhydrous oxalic acid at ∼100°C for 4-12 h. (Aromatic aldehydes afforded mixtures of nitrile and amide.) The transformation is apparently (kinetically) driven by the coupled decomposition of oxalic acid (to CO+CO₂) via the fragmentation of an intermediate oxime mono-oxalate. However, an alternative pathway, mechanistically analogous to the Schmidt reaction, is not only equally likely but may well be general for the Beckmann rearrangement.     

A Novel Method for Beckmann Rearrangement of Oximes with Silica Sulfuric Acid under Mild Condition

The conversion of ketoxime into corresponding amide, known as the Beckmann rearrangement, is a common method used in organic chemistry and is also a topic of current interest. It accomplishes both the cleavage of carbon-carbon bond and the formation of a carbon-nitrogen bond, and represents a powerful method particularly for manufacture ε-caprolactam in chemical industry. This reaction, however, generally requires high reaction temperature, strong Br?nsted acid and dehydrating media, causing …     

Syntheses of 2-arylated 1-benzazocines via Beckmann rearrangement

One-step and highly efficient syntheses of 2-aryl-1-benzazocines via Beckmann rearrangement of 5H-benzocyclohepten-5-one oxime mesylates in dry toluene was described, in which aryl Grignard reagents were used for the first time to induce Beckmann rearrangement directly without any additional protic agents. Iodotrimethylsilane was also employed to promote Beckmann rearrangement of the mesylates, followed by the treatment of the intermediate imidoyl iodide with phenylmagnesium bromide to complete the synthesis of benzazocines.     

Beckmann重排法合成抗癫痫药加巴喷丁

由亚甲基环己烷出发, 采用[2＋2]环加成和Beckmann重排策略, 经四步反应在比较温和的条件下合成了抗癫痫药物加巴喷丁盐酸盐.     

磺酸树脂在樟脑肟贝克曼裂解反应中的催化作用

我们发现以磺酸树脂作为固体酸催化樟脑肟贝克曼裂解反应可以生成α-龙脑烯腈.考察了溶剂、催化剂用量、反应温度和反应时间等对反应的影响.在优化条件下樟脑肟可以完全转化,α-龙脑烯腈选择性高达90.5%.动力学研究表明,樟脑肟在磺酸树脂催化下的贝克曼裂解反应服从准一级动力学模型,经过最小二乘法求得反应的表观活化能为64.6kJ/mol.     

钴催化的高效贝克曼重排反应

利用廉价易得的氟硼酸钴水合物, 在温和、 无添加剂的空气条件下, 高效催化酮肟衍生物的贝克曼重排反应, 底物的普适性和官能团的兼容性均较理想, 产物收率最高达97%. 基于该高活性的氟硼酸钴水合物, 实现了10 g级二苯甲酮肟的贝克曼重排反应, 收率为71%. 同时, 也实现了钴催化酮类衍生物和盐酸羟胺的一步法贝克曼重排反应, 产物最高收率为94%, 反应体系中无溶剂及添加剂, 反应体系的原子经济性和底物普适性较好.     

Titanium cation-exchanged montmorillonite as an active heterogeneous catalyst for the Beckmann rearrangement under mild reaction conditions

Titanium cation-exchanged montmorillonite acts as an efficient heterogeneous catalyst for the Beckmann rearrangement of a wide range of ketoximes including aromatic, aliphatic, and alicyclic ketoximes under mild reaction conditions. After the rearrangement reaction, titanium cation-exchanged montmorillonite is easily separated by simple filtration, and can be reused with retention of high efficiency.     

Silicalite-1空心球材料制备及其在Beckmann重排反应中催化应用研究

以碳微球作为硬模板、纳米Silicalite-1分子筛作为壳层,采用水热法合成了Silicalite-1空心球材料。采用XRD、SEM、FT-IR、N_2吸附、29Si M AS NM R、TG、XPS等技术对催化剂的物相、形貌和性能等进行表征,发现该空心材料具有较高的结晶度、发达的多级孔道结构和丰富的表面羟基。与传统方法制备的Silicalite-1分子筛催化剂相比,Silicalite-1空心材料在环己酮肟Beckmann重排反应中表现出优异的催化性能,使环己酮肟的转化率达99%、己内酰胺的选择性达94%,同时催化剂保持极佳的稳定性。研究表明,Silicalite-1空心材料中具有的大量巢式硅羟基和末端硅羟基是Beckmann重排反应的主要活性位,且可通过简单焙烧再生实现羟基活性位的完全恢复。     

钛硅分子筛催化气相环己酮肟贝克曼重排反应

 对比研究了具有MFI结构的TS－1，silicalite－1，Al－ZSM－5和B－ZSM－5分子筛对气相环己酮肟贝克曼重排反应的催化性能．结果显示，TS－1适宜用作重排反应的催化剂，而含骨架B或Al的ZSM－5分子筛的催化性能较差，表明将Ti引入至sili－calite－1有利于改善其对环己酮肟重排反应的催化性能．反应氛围（溶剂、载气和原料添加物）对TS－1催化性能的影响规律说明，弱酸性气体的存在有利于TS－1对环己酮肟的活化与己内酰胺的选择性生成．优化的反应氛围包括以甲醇或乙醇为溶剂，二氧化碳为载气，以及醋酸为原料添加物．     

氢氟酸后处理对Silicalite-1催化环己酮肟气相Beckmann重排反应性能的影响

 研究了氢氟酸后处理对 silicalite-1 催化环己酮肟气相Beckmann重排反应性能的影响. 结果表明,经适当浓度的氢氟酸溶液处理后,催化剂的选择性和稳定性都明显改善. 其中, silicalite-1 原粉先经硝酸铵预处理后再进行氢氟酸后处理所得到的催化剂催化性能最好,反应53 h后环己酮肟的转化率仍保持在96%左右,己内酰胺的选择性高达96.1%. XRD, FT-IR和 29Si MAS NMR的结果表明,较高的具有氢键相互作用的硅羟基与孤立硅羟基的比例值对环己酮肟气相Beckmann重排反应有利,同时, silicalite-1 表面硅原子的排布方式对该反应也有重要影响.     

Abnormal Beckmann rearrangement of steroidal α-chlorocyclobutanone oximes: the fragmentation-substitution reaction

α,α-Dichlorocyclobutanones of various substitution patterns, readily available by the thermal cycloaddition of dichloroketene to steroid olefins, were selectively dehalogenated and further transformed to α-chlorocyclobutanone oximes. In contrast to the Beckmann rearrangement of the α-unsubstituted oximes, α-chlorocyclobutanone oximes, on treatment with thionyl chloride in benzene, gave normal and abnormal reaction products. In all reactions studied, the Beckmann fragmentation-substitution was the major process. The rearrangement of α-chlorocyclobutanone oximes is the key step of the novel method for geminal functionalization of carbonyl carbon atom in ketones and regioselective vicinal functionalization of unsymmetrical olefins. The regiochemistry observed in the rearrangements is supported by semiempirical calculations (AM1).     

A concise approach to chiral chromenes based on levoglucosenone

Levoglucosenone, a chiral α,β-unsaturated ketone derived from cellulose, undergoes a stereoselective domino oxa-Michael-aldol reaction with 2-hydroxybenzaldehydes affording optically active pyrano[3,4-b]chromenes. The latter are further converted into 2H-chromenes via a Beckmann fragmentation reaction.     

Carbon Tetrabromide/Triphenylphosphine‐Activated Beckmann Rearrangement of Ketoximes for Synthesis of Amides

An efficient Beckmann rearrangement of ketoximes was developed using carbon tetrabromide/triphenylphosphine as an organocatalyst without addition of any acids or metals. The reaction showed good functional group tolerance and gave various amides in moderate to good yields.     

Silica sulfate as a recyclable and efficient catalyst for Beckmann rearrangement under microwave irradiation

Silica sulfate has been proved to be an efficient and recyclable catalyst for Beckmann rearrangement of a variety of oximes in acetone under microwave irradiation. This protocol has advantages of high conversion, high selectivity, short reaction time, no environmental pollution, and simple work-up procedure.     

Facile Synthesis of Thioamides via P2S5‐Mediated Beckmann Rearrangement of Oximes

A facile and efficient approach to the synthesis of secondary thioamides from ketoximes via Beckmann rearrangement has been established, using phosphorus pentasulfide as a dehydrating and thiating agent. It is also efficient for the preparation of primary thiobenzamide from benzaldoxime. This approach features simple‐operation, easy‐control and good to excellent yields.     

Multicatalytic Beckmann rearrangement of 2-hydroxylarylketone oxime: Switchable synthesis of benzo[d]oxazoles and N-(2-hydroxylaryl)amides

A switchable synthesis route is developed for benzo[d]oxazole derivatives and (2-hydroxylaryl)benzamide from 2-hydroxylbenzeneketoxime using organomolecules (BOP-Cl, and CNC) and Lewis acid cocatalyzed Beckmann rearrangement (BR) reaction. Further, this reaction is switched using different organocatalysts.     

Polystyrene-supported phosphine oxide-catalysed Beckmann rearrangement of ketoximes in 1,1,1,3,3,3-hexafluoro-2-propanol

A polystyrene-supported phosphine oxide-catalysed Beckmann rearrangement of ketoximes in 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) has been developed. Good substrate compatibility, mild reaction conditions, good yields as well as the reusability of the catalyst/solvent made this procedure more environmentally benign.     

A novel task-specific ionic liquid for Beckmann rearrangement: a simple and effective way for product separation

Under mild conditions and without any additional organic solvents, Beckmann rearrangement of ketoximes was performed in a novel task-specific ionic liquid consisting sulfonyl chloride. Especially for the conversion of cyclohexanone oxime to ε-caprolactam, ε-caprolactam has good solubility in water while the task-specific ionic liquid is immiscible with water, therefore, ε-caprolactam could be easily separated from the reaction system by water extraction.     

High-Yield Method for the Preparation of 1,3,4,5-Tetrahydro-7-methoxy-2H-1-benzazepin-2-one with Excellent Regio- and Stereoselectivity

We have surveyed the effects of different acid catalysts, reaction times, and temperatures on the yield, regioselectivity, and stereoselectivity and calculated the ketoxime isomerization and activation energy of the title compound. A facile synthetic procedure with good yields and good regio- and stereoselectivity for Beckmann rearrangement of oxime sulfonate with ZnCl₂ in the presence of solvent is developed.     

A new and concise way to enamides by fluoroalkanosulfonyl fluoride mediated Beckmann rearrangement of α,β-unsaturated ketoximes

The reaction of α,β-unsaturated ketoximes with fluoroalkanosulfonyl fluorides in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) underwent the Beckmann rearrangement smoothly to afford the corresponding acid-sensitive enamides in moderate to excellent yields, which provides a new efficient method for the preparation of acid-sensitive enamides.