供体-受体氮杂环丙烷碳-碳键断裂的环加成反应研究进展

氮杂环丙烷有两种不同的开环方式:一种是碳-氮键断裂开环,另一种是碳-碳键断裂开环.其中,氮杂环丙烷以碳-氮键断裂的反应已经有很多综述报道.主要概述了近二十年来供体-受体(Donor-Acceptor,D-A)氮杂环丙烷以碳-碳键断裂的环加成反应研究进展.在合适催化剂作用下,D-A氮杂环丙烷经碳-碳键断裂开环形成亚胺叶立德,该叶立德可以和醛、亚胺、烯烃、炔烃和吲哚等发生[3+n]环加成反应.     

镍催化氮杂环丙烷的开环偶联反应研究

氮杂环丙烷类化合物是重要的有机合成子,其广泛存在于各种有机合成反应当中.因其独特的三元环结构,致使其具有较大的环张力.通常氮杂环丙烷类化合物可以与各种亲核试剂反应,合成各种传统方法难以合成的β-位取代的胺类化合物,其中包括氨基醇、氨基醚以及二胺类化合物.通过亲核试剂开氮杂环丙烷的反应研究已经相当成熟,此处不再赘述.此外,过渡金属催化的C—N活化是一类重要的合成方法.作为C—N活化重要底物,过渡金属催化氮杂环丙烷的开环偶联反应取得长足的发展.尤其是近十年来,镍催化氮杂环丙烷的开环偶联反应不断涌现.基于此,综述了镍催化在氮杂环丙烷开环偶联反应中的研究进展和设计原则,重点介绍氮杂环丙烷的开环原理,对比不同取代的氮杂环丙烷区域选择性,总结不同催化模式下的共性.本综述将从以下三个方面介绍氮杂环丙烷的开环偶联反应:其一是单独的镍催化模式;其二是光/镍协同共催化模式;其三则是电化学促进的镍催化模式.对于氮杂环丙烷的开环模式则可以分为:镍催化的SN2型亲核开环模式、卤素离子亲核开环模式以及电化学还原模式.     

酸性离子液体催化的羟基化合物对N-对甲苯磺酰基氮杂环丙烷的开环反应

本文研究了羟基化合物对两种类型N-对甲苯磺酰基氮杂环丙烷的开环反应。在功能性离子液体[hmim]HSO4存在条件下,氮杂环丙烷与醇反应,以中等到高的产率和非常高的区域选择性得到对应的β-胺基醚。并且离子液体[hmim]HSO4可以循环使用。     

非对称氮杂环丙烷的亲核开环反应及其区域选择性

本文系统地总结了各类亲核试剂对非对称氮杂环丙烷(吖丙啶)的亲核开环反应及开环的区域选择性.氮杂环丙烷亲核开环的区域选择性是一种空间效应和电子效应平衡的结果,非芳基和非烯基取代的氮杂环丙烷的亲核开环通常发生在氮杂环丙烷取代少的碳原子上,空间效应起主导作用;而芳基和烯基取代的氮杂环丙烷的亲核开环通常发生在氮杂环丙烷芳甲位和烯丙位的碳原子上,电子效应起主导作用,烯基取代的氮杂环丙烷的亲核开环还可以发生在烯基的β-碳原子上;分子内的亲核开环反应主要受成环时环大小的控制,成环时的倾向是五元环>六元环>七元环.对于亲核试剂,一般的亲核试剂也同时受电子效应和空间效应的影响; 而亲核性强的亲核试剂通常只受空间效应的影响.容易生成稳定自由基的亲核试剂容易发生单电子转移机理的开环反应,生成相当于亲核试剂进攻氮杂环丙烷中取代多的碳原子得到的开环产物.     

碳亲核试剂对氮杂环丙烷的开环反应研究进展

综述了各种碳亲核试剂对氮杂环丙烷的开环反应研究进展,主要包括炔、腈、芳烃、芳香杂环化合物、活泼亚甲基和有机金属试剂等作为碳亲核试剂发生的开环反应,并对其发展方向进行了展望.     

三氟亚乙基取代的N-苯甲酰基氮杂环丙烷的合成

发展了一种制备三氟亚乙基取代的N-苯甲酰基氮杂环丙烷的新颖方法. 三氟甲基取代的炔丙胺化合物1在盐酸作用下脱去叔丁基亚磺酰基得到三氟甲基炔丙胺盐酸盐2, 当用NaOH作碱对2进行苯甲酰化反应时意外地以中等产率获得了N-苯甲酰基-2-三氟亚乙基氮杂环丙烷类化合物3a～3c. 在类似条件下也可以从1出发采用“一锅法”制得氮杂环丙烷3d和3e. 化合物3b可以在酸催化下发生开环反应得到化合物6b. 化合物3和6的结构经IR, 1H NMR, 19F NMR, MS, HRMS和元素分析进行确证.     

金属配合物催化氮杂环丙烷化和饱和C-H键氮插入反应

氮杂环丙烷是有机合成之砌块,其合成方法是重要的研究课题.本文全面介绍了近20年来的氮杂环丙烷的金属配合物催化合成,尤其是以氮宾转移到烯烃或碳宾加成到亚胺 为合成途径的氮杂环丙烷化催化反应的研究进展,还包括该反应在金属催化时发生的竞争性插入到饱和C-H键的反应.     

烯丙型膦叶立德与卟啉铁卡宾反应: 催化的高效、高选择性的分子间卡宾对烯烃C—H键形式插入反应

叶立德作为带有特殊离去基团的碳负离子(亲核试剂)被广泛应用于有机合成研究. 传统的叶立德参与的反应主要有叶立德同亲电的羰基化合物、亚胺以及烯烃的反应, 分别生成烯烃和环氧化合物、氮杂环丙烷化合物以及环丙烷化合物. 亲电的金属卡宾作为一类重要的亲电试剂, 其同叶立德的反应研究报道则很少. 最近, 中国科学院上海有机化学研究所唐勇等发现, 酯基稳定的卟啉铁卡宾可以高效、高选择性地插入到烯丙型膦叶立德的C—H键中. 机理研究表明, 反应经历环丙烷化-开环重排反应的串联过程. 在此基础上, 高立体选择性地实现了1,1,4-三取代共轭丁二烯衍生物的合成, 反应具有很好普适性. 该发现提供了叶立德与金属卡宾(亲电试剂)反应的一种新模式.     

二碘化钐促进的硒代酯的合成

用SmI2/THF/HMPA体系在室温下使二芳基二硒醚中的Se-Se键还原断裂成硒负离子物种, 继而与酸酐作用得到硒代酯, 该反应条件温和中性, 产率良好, 提供了合成硒代酯的一个新途径。     

非对称氮杂环丁烷的区域选择性开环反应

本文系统总结了非对称氮杂环丁烷的区域选择性开环反应。氮杂环丁烷的开环反应主要包括亲核开环、Stevens重排扩环及消除开环反应等。其中,亲核开环反应是氮杂环丁烷的主要开环方式。开环的区域选择性与氮杂环丁烷取代基结构密切相关。氮杂环丁烷相对比较稳定,其开环通常需要路易斯酸催化或者先转化成季铵盐才可以发生,因此,其开环反应的区域选择性受电子效应的影响比较明显。邻位带有不饱和官能团的氮杂环丁烷及其季铵盐一般发生氮原子与带有不饱和官能团的碳原子之间化学键的断裂,这是因为如芳基、烯基、氰基、酰基、甲酸酯基和甲酰胺基等不饱和官能团的共轭效应可以稳定其连接的碳原子在开环时形成的过渡态或者中间体,使该C—N键更容易断裂。如亲核开环反应,亲核试剂一般进攻芳甲位、烯丙位或连有氰基或甲酸酯基或甲酰胺基的邻位碳原子,电子效应起主要作用。对于2-烷基取代的氮杂环丁烷及其季铵盐,大位阻或者亲核性强的亲核试剂的开环反应一般发生在位阻小的氮邻位碳原子,空间效应起主要作用。分子内的亲核开环反应主要受反应过程中环大小的控制,一般有利于经过三元环、五元环、六元环和七元环过程开环得到开环产物。氮杂环丁烷是一类非常重要的含氮杂环化合物,通过总结和分析氮杂环丁烷的开环反应及其区域选择性,可以更好地认识和利用这类反应,通过有效地预测和控制开环反应的方向,来制备所需的有机化合物。希望本文能够促进氮杂环丁烷开环反应在有机化学中的发展与应用。     

Construction of three contiguous tertiary stereocenters from aziridines in one step

A range of active methylene nucleophiles were found to participate in ring-opening of tosylated aziridines under mild phase-transfer catalyzed conditions. High isolated yields coupled with a 1:1 reaction stoichiometry and high levels of relative stereocontrol are distinguishing features of this method. The products are obtained without epimerization, underscoring the optimal conditions afforded by the phase-transfer catalysis for connecting active methylene nucleophiles and weakly electrophilic N-tosylated aziridines.     

Chiral Aziridines—Their Synthesis and Use in Stereoselective Transformations

The preparation of enantiomerically pure compounds is one of the major areas of organic chemistry. Much emphasis is placed on the elaboration of naturally occurring starting materials and on the development of techniques for enantio-selective transformations of achiral substrates. In this field, chiral aziridines form an attractive class of compounds, since they are available in enantiomerically pure (or highly enriched) form by a variety of procedures and can be used for asymmetric synthesis in a number of different ways. The chemistry of aziridines is dominated by ring-opening reactions, the driving force for which is relief of ring strain. By suitable choice of sub-stituents on the carbon and nitrogen atoms, excellent stereo- and regiocontrol can be attained in ring-opening reactions with a wide variety of nucleophiles, including organometallic reagents; this makes chiral aziridines useful as substrates for the synthesis of important biologically active species including alkaloids, amino acids, and /Mactam antibiotics. Substrate-controlled diastereo-selective synthesis is also possible by use of aziridines as removable chiral auxiliaries, while metalation at a ring carbon atom allows aziridines to be used as chiral reagents for asymmetric synthesis. Chiral bisaziridines can act as ligands for transition metals, and applications in the challenging field of enantioselective catalysis can be envisioned. Today, the exclusion of three-membered carbo- and heterocycles from the arsenal of the organic chemist is inconceivable.

1 H. Heimgartner, Angew. Chem. 1991 , 103, 271; Angew. Chem. Int. Ed. Engl. 1991 , 30, 238.

     

Efficient and regioselective ring-opening of arylaziridines with alcohols,thiols, amines and N-heteroaromatic compounds using sulphated zirconia

Sulphated zirconia is an efficient catalyst for the regioselective ring-opening of aryl-substituted aziridines. This heterogeneous catalyst can be used several times without loss of activity and is compatible with a variety of acid sensitive and slightly basic nucleophiles.     

Ring-opening reactions of nonactivated aziridines catalyzed by tris(pentafluorophenyl)borane

The ring-opening reactions of nonactivated aziridines with amine nucleophiles are efficiently catalyzed by tris(pentafluorophenyl)borane leading to derivatives of trans-1,2-diamines in high yields. A mechanistic investigation of the reaction suggests that in situ formed [(C(6)F(5))(3)B(OH(2))].H(2)O catalyzes the opening through a Br?nsted acid manifold.     

Aziridines from intramolecular alkene aziridination of sulfamates: reactivity toward carbon nucleophiles. application to the synthesis of spisulosine and its fluoro analogue

Catalytic intramolecular alkene aziridination of sulfamate is an emerging methodology for the asymmetric synthesis of chiral functionalized amines involving the formation of bicyclic aziridines. This study demonstrates the ability of the latter to undergo ring-opening with various carbon nucleophiles: Grignard reagents, lithium salts of terminal alkynes, dithiane, malonate. These S(N)2-type reactions occur with high levels of regio- and chemoselectivity to generally afford seven-membered cyclic sulfamidates in good yields. Carbon nucleophiles have also been found to react with these sulfamidates provided that the sulfamate ester has been previously activated by introduction of a tosyl substituent on the NH group. The versatility of this strategy has been illustrated with the syntheses of spisulosine and its fluoro analogue.     

非对称环硫乙烷的区域选择性亲核开环反应

环硫乙烷与它的氧类似物环氧乙烷和氮类似物氮杂环丙烷一样,是一类重要的有机合成中间体,在医药和农用化学品工业领域也得到广泛应用。通过开环和异构化反应,还广泛用于制备硫醇和硫醚等含硫化合物。本文总结了常用亲核试剂对非对称环硫乙烷的亲核开环反应及其区域选择性。环硫乙烷的亲核开环反应通常只受空间效应影响,亲核试剂进攻非对称环硫乙烷位阻小的碳原子,对于烯基取代的环硫乙烷有时可以进攻烯基的β碳原子发生SN2’开环反应。强亲核性的亲核试剂容易致使环硫乙烷脱硫生成烯烃,而亲核性相对较弱的亲核试剂容易发生多聚反应生成多硫醚。在Lewis酸存在下,电子效应会对开环反应的区域选择性产生影响,甚至起主导作用。虽然烷基取代环硫乙烷在Lewis酸存在下的开环仍然主要发生在其取代基少的碳原子上(位阻控制),但受电子效应影响,芳基和烯基取代环硫乙烷的亲核开环,其亲核试剂一般倾向于进攻环硫乙烷的芳甲位和烯丙位碳原子(电子效应控制)。     

New insights into the mechanism of palladium-catalyzed allylic amination

A comparative investigation into palladium-catalyzed allylic amination of unsubstituted aziridines and secondary amines has been carried out. The use of NH aziridines as nucleophiles favors formation of valuable branched products in the case of aliphatic allyl acetates. The regioselectivity of this reaction is opposite to that observed when other amines are used as nucleophiles. Our study provides evidence for the palladium-catalyzed isomerization of the branched (kinetic) product formed with common secondary amines into the thermodynamic (linear) product. In contrast, the branched allyl products obtained from unsubstituted aziridines do not undergo the isomerization process. Crossover experiments indicate that the isomerization of branched allylamines is bimolecular and is catalyzed by Pd(0). The reaction has significant solvent effect, giving the highest branched-to-linear ratios in THF. This finding can be explained by invoking the intermediacy of sigma-complexes, which is consistent with NMR data. The apparent stability of branched allyl aziridines towards palladium-catalyzed isomerization is attributed to a combination of factors that stem from a higher degree of s-character of the aziridine nitrogen compared to other amines. The reaction allows for regio- and enantioselective incorporation of aziridine rings into appropriately functionalized building blocks. The resulting methodology addresses an important issue of forming quaternary carbon centers next to nitrogen. The new insights into the mechanism of palladium-catalyzed allylic amination obtained in this study should facilitate synthesis of complex heterocycles, design of new ligands to control branched-to-linear ratio, as well as absolute stereochemistry of allylamines.     

Tributylphosphine: a remarkable promoting reagent for the ring-opening reaction of aziridines

Tributylphosphine was found to be an effective promoting reagent for ring opening of a variety of aziridines and nucleophiles to produce anti-bifunctional products in good to excellent yield. The study showed that the reaction is initiated through the attack of tributylphosphine as a nucleophile at the carbon atom of the aziridine ring.     

Ynolate chemistry. Reaction of a silylynolate with aziridines leading to gamma-lactams.

A silylynolate, generated via the carbonylation of lithium silyldiazomethane, was reacted with N-tosyl aziridines to produce various five-membered lactams in good yields. The key step of this reaction involves the ring-opening ketenylation of aziridines by the silylynolate. The reaction proceeded in a highly stereoselective manner, and ketenylation took place at the less hindered carbon. When treated with aldehydes prior to protonation, the alpha-silylated lactam enolates gave alpha-vinylidene gamma-lactams. These reactions represent a unique path to the generation of and for controlling the reactivity of a rare class of reactive intermediates, namely, acyllithium derivatives and ynolates.     

Stereocontrolled intramolecular aziridination of glycals: ready access to aminoglycosides and mechanistic insights from DFT studies

Stereocontrolled intramolecular aziridination of the glycal-derived sulfamates offers a highly efficient strategy to divergently prepare aminoglycosides. Rhodium-catalyzed nitrogen-atom transfer to C==C bonds formed semistable aziridines, which were subjected to various nucleophiles (C, O, S, and N) to give cyclic sulfamate-containing aminosugar derivatives selectively. The second nucleophilic displacement of sulfonyloxy moieties of [1,2,3]-oxathiazepane-2,2- dioxides allows straightforward access to aminoglycosides with selective alpha- or beta-linkages. This approach is operationally simple, complements existing methods, and is a versatile protocol for the synthesis of polyfunctionalized amino sugars. In addition, the mechanism of the rhodium-catalyzed intramolecular aziridination of glycals and its ring-opening reaction was extensively studied by using DFT calculations.