Diastereoselective synthesis of cyclic 1,3-aminoalcohols bearing CF3(CCl3)-groups

An aldol-type reaction of cyclic imines and cyclic lactims with carbonyl compounds activated by electron withdrawing trifluoromethyl or trichloromethyl groups proceeded without any catalyst under mild condition. β-Hydroxymethyl substituted cyclic imines or imidates are formed as a result of the reaction. The reduction of the prepared imines leads stereoselectively to the cyclic 1,3-aminoalcohols. Application of methyl trifluoropyruvate in this transformation opens an opportunity for the synthesis of γ-aminoacids derivatives which contain pyrrolidine moiety.     

氧化铝负载的银纳米颗粒高选择性催化合成亚胺(英)

The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al_2O_3 was studied.The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines.The reactions were performed under mild conditions and afforded the imines in high yield(up to 99%) without any byproducts other than H_2O.The highest activity was obtained over 5 wt%Ag/Al_2O_3 in toluene with air as oxidant.The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H_2 in the gas phase.The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis.     

An Efficient Prins Cyclization for Stereoselective Synthesis of Tetrahydropyran from Imines and Homoallyl Alcohols

An unprecedented protocol has been developed for the efficient synthesis of substituted tetrahydropyrans via a bismuth‐promoted Prins cyclization of imines with homoallyl alcohols. In the presence of 40 mol% BiCl₃, a wide variety of imines react smoothly with homoallyl alcohols at room temperature to give the corresponding 4‐chlorotetrahydropyran derivatives in good to excellent yields.     

氧化铝负载的银纳米颗粒高选择性催化合成亚胺(英)

The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al₂O₃ was studied.The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines.The reactions were performed under mild conditions and afforded the imines in high yield（up to 99%） without any byproducts other than H₂O.The highest activity was obtained over 5 wt%Ag/Al₂O₃ in toluene with air as oxidant.The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H₂ in the gas phase.The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis.     

Synthesis of Poly-Substituted Pyridines via Noble-Metal-Free Cycloaddition of Ketones and Imines

An eco-friendly and noble-metal-free formal [4+2] cycloaddition reaction was developed for the efficient synthesis of biologically interesting poly-substituted pyridines from easily available ketones and imines, whereby two sequential C−C bonds are formed. The given approach features a unique synthetic strategy of imines and ketones with wide substrate scope, good functional group tolerance, mild conditions and operational simplicity, which represents a more direct pathway to synthesize poly-substituted pyridines than traditional methods.     

Direct synthesis of imines from gem-dibromomethylaryl derivatives: application to unsymmetrically substituted bipyridine frameworks

An efficient methodology for the one-pot synthesis of imines is described starting from gem-dibromomethylaryl compounds and primary amines. The synthesis was applied to various aliphatic mono- and polyamines as well as to electron-rich anilines. The protocol was extended to 6-bromo-5'-dibromomethyl-2,2'-bipyridine to afford the corresponding imines. With n-propyl- and n-decylamine, further conversion, in three steps, to the corresponding 6-carboxy-5'-alkylaminomethyl-2,2'-bipyridine derivatives was selectively achieved, providing new tridentate ligands that may find interesting applications for the complexation of lanthanide(III) cations in their anionic or zwitterionic form.     

Facile iodine(III)-induced oxidative cycloaddition of N-sulfonyl imines with methylene compounds under neutral conditions

An efficient oxidative cycloaddition of N-sulfonyl imines with methylene compounds using PhIO with a catalytic amount of KI under neutral conditions, which affords 2,2-difunctionalized aziridines in good to excellent yields, is reported.     

FeCl3-promoted formation of C–C bonds: synthesis of substituted quinolines from imines and electron-deficient alkynes

An efficient method for the synthesis of substituted quinolines is described. By FeCl₃-promoted C–C bond formation, 2,3-disubstituted and 2,3,4-trisubstituted quinolines were successfully synthesized from the reaction between imines and electron-deficient alkynes in good yields. The reaction can also be performed in a sequential three-component manner by using aromatic amines and aromatic aldehydes instead of the corresponding imines.     

A Porphyrin-Based Covalent Organic Framework for Metal-Free Photocatalytic Aerobic Oxidative Coupling of Amines

Imines are important intermediates in drug synthesis. Photocatalytic aerobic oxidative coupling of amines has been considered as a clean and promising way to produce imines and has attracted great attention. Herein, we designed and synthesized a novel two-dimensional porphyrin-based covalent organic framework (Por-BC-COF) which adopts an AA stacking mode with excellent crystallinity, high Brunauer–Emmett–Teller surface areas (1200 m² g⁻¹), wide light absorption range (200–1300 nm) and good stability in a variety of organic solvents. Por-BC-COF can be used as a metal-free heterogeneous photocatalyst for the photocatalytic oxidation of amines to imines under visible light and red light with a high yield (97 %). This work presents a novel and efficient COF photocatalyst in the application of light-driven organic synthesis.     

纳米二氧化铈催化制备亚胺

近年来,金属氧化物的晶面效应及其独特的催化性能引起研究者的广泛关注.其中,二氧化铈(CeO2)因具有储放氧性质、易于形成氧空位等特点,在诸多领域得到应用,尤其是作为催化剂,可用作活性相、载体、复合催化材料等. CeO2的晶面效应主要由于晶面上氧空位的性质引起的.目前,这方面的研究主要集中在高温条件下氧空位的动态转化过程,如水汽变换反应、有机物脱除等.但是高温下CeO2中氧空位的活泼性,增加了晶面效应的复杂性.因此,利用低温液相有机反应作为探针,研究晶面效应是一种可靠的解决方案.我们近些年的工作研究了CeO2不同晶面上的酸性及催化水解性能,在本研究中,我们提出在温和条件下, 采用有机探针反应,研究不同晶面的氧化还原性质.亚胺类化合物作为一类重要的含氮有机中间体,在生物、农药、医药等领域中具有重要应用.传统的亚胺合成方法是将醛类化合物或酮类化合物与胺类在酸催化剂的作用下直接缩合.近年来出现了新的亚胺合成方法,例如通过胺类氧化脱氢、炔烃的氢胺化、醇胺脱氢/氧化偶联等,其中醇胺脱氢/氧化偶联的方法因具有原料廉价易得、过程清洁等优点,而成为研究热点.最近, Masazumi Tamura等研究发现CeO2能够在温和条件下高效催化醇胺氧化偶联制亚胺,通过一系列表征发现CeO2的高活性主要由于其氧空位中存在丰富的活性氧物种.然而, CeO2的晶面效应及其在此反应中的催化性能,以及不同晶面上的氧化还原性质还有待进一步的研究.本文研究了CeO2的晶面效应及其在醇胺氧化偶联制亚胺反应中的催化性能.在温和的反应条件下(60 oC), CeO2能够高效催化苯甲醇与苯胺反应制备亚胺,并且对底物具有很好的普适性,在催化一系列醇与胺氧化偶联制亚胺的反应中,对于大部分底物,醇类化合物的转化率可达89%以上,亚胺类化合物的选择性可达90%以上.通过水热合成法分别制备了棒状CeO2、立方体CeO2和八面体CeO2,并通过X射线衍射、透射电子显微镜和高分辨透射电子显微镜确证了其结构和形貌,结果表明三种形貌的CeO2均为纯相的CeO2,其中棒状CeO2暴露(110)和(100)晶面,立方体CeO2暴露(100)晶面,八面体CeO2暴露(111)晶面.并以苯甲醇氧化反应和苯甲醇与苯胺反应为探针研究了其催化性能.结果发现：不同形貌的CeO2具有显著不同的催化活性,其中棒状CeO2表现出最优异的催化性能,立方体CeO2和八面体CeO2次之.通过Raman光谱表征了不同形貌CeO2的氧空位性质并比较了它们的氧空位浓度.结果发现：棒状CeO2的氧空位浓度相对值(A595/A462)为0.077,高于立方体CeO2和八面体CeO2.通过比较分析计算可知,在CeO2(110),(100)和(111)三种晶面中,(110)晶面因其具有最多的氧空位而表现出最高的催化活性和优异的氧化还原性质,(110)晶面上亚胺的生成速率为4.618 mmol/(g·h),分别为(100)晶面和(111)晶面上的32倍和49倍.该研究有助于提高认识CeO2基催化材料的低温氧化还原性质.     

One-pot nitro-Mannich/hydroamination cascades for the direct synthesis of 2,5-disubstituted pyrroles using base and gold catalysis

An efficient, easy to perform, one-pot reaction cascade for the synthesis of 2,5-disubstituted pyrroles from p-toluenesulfonyl protected imines and 4-nitrobut-1-yne under a combination of base and gold(III) catalysis is reported.     

Efficient and versatile synthesis of indoles from enamines and imines by cross-dehydrogenative coupling

Complement for Fischer: An efficient palladium-catalyzed indole synthesis proceeds by the intramolecular cross-dehydrogenative coupling of N-aryl imines under mild conditions using molecular oxygen as the sole oxidant. This practical method relies on anilines and ketones as starting materials (and thus the same retrosynthetic disconnection as the Fischer indole synthesis) and will likely become a popular route.     

A new ‘one-pot’ synthesis of 2-substituted 3-nitro pyrrolidines through a multicomponent domino reaction

An efficient ‘one-pot’ synthesis of the title compounds based on a multicomponent domino reaction between imines and 3-nitro-1-propanol methanesulfonate has been developed.     

Mannich Reaction of Indole with Cyclic Imines in Water

An efficient MsOH promoted direct Mannich reaction of indoles with α-nonsubstituted aliphatic cyclic imines has been developed. The reactions were performed in water and the obtained piperidin-2-yl-indoles act as a useful precursor for the synthesis of various alkaloid-like derivatives.     

Synthesis of 2-aryl-4-chloropyrroles via ring expansion of 2-aryl-1-chlorocyclopropanecarbaldehydes

An efficient electrophile-induced ring opening of 2-aryl-1-chlorocyclopropanecarbaldehydes is described towards halogenated butanals, which were converted to the corresponding imines. These α,α,γ-trichloroimines proved to be good substrates for a nucleophile-induced ring closure towards 2-pyrrolines as versatile synthons for the synthesis of pyrroles bearing physiologically interesting substitution patterns.     

Chemoselective aerobic oxidation of 2-amino-N-benzylanilines into N-(2-aminophenyl)imines via a nitroxide-free copper catalysis

Chemoselective oxidative synthesis of N-(2-aminophenyl)imines from 2-amino-N-benzylanilines was accomplished through combined use of O₂(air) and copper salt. This transformation was performed at room temperature, and the mild oxidation was efficient and chemoselective without using nitroxyl radicals and ligands.     

Atroposelective Synthesis of 3,3’‐Bisindoles Bearing Axial and Central Chirality: Using Isatin‐Derived Imines as Electrophiles

An atroposelective synthesis of a new class of 3,3’‐bisindoles bearing axial and central chirality has been established via catalytic asymmetric addition reactions using isatin‐derived imines as electrophiles (23 examples, up to 80% yield, > 95 : 5 dr, 98 : 2 er). This approach takes advantage of chiral phosphoric acid‐catalyzed dynamic kinetic resolution of 2‐substituted 3,3’‐bisindoles via nucleophilic addition of such substrates with isatin‐derived imines. In this approach, isatin‐derived imines acted as a class of competent electrophiles due to their high reactivity and bulky size, which provided an easy access to axially chiral 3,3'‐bisindoles incorporated with a biologically important chiral 3‐aminooxindole unit. This approach has greatly expanded the generality and applicability of the strategy of dynamic kinetic resolution for the synthesis of enantioenriched 3,3’‐bisindole derivatives bearing both axial and central chirality.     

CuI/La(OTf)3 catalyzed, one-pot synthesis of isomeric ellipticine derivatives in ionic liquid

An efficient method for one-pot synthesis of isomeric ellipticine derivatives through CuI/La(OTf)₃ catalyzed sequential inter/intramolecular cyclization of substituted alkynes with imines followed by aromatization is reported in good to excellent yields.     

A short formal synthesis of three epimers of penmacric acid

An extremely short formal synthesis of three epimers of penmacric acid is accomplished starting from pyroglutamate in one or two steps. Stereochemical outcome in the reaction of Li and Ti enolates of pyroglutamate with imines is found to be dependent on both chelation and steric factors.     

Direct synthesis of protected diethyl 1,2-diaminoalkylphosphonates

An efficient, diastereoselective synthesis of 5-substituted (2-thioxo-imidazolidin-4-yl)phosphonic acid diethyl esters from metallated diethyl isothiocyanatomethylphosphonate and activated imines has been developed. The three-step transformation of imidazolidine-2-thione derivatives into 1,2-diaminoalkylphosphonic acids is also described.