金属催化硫醚的不对称氧化研究进展

手性金属络合物催化硫醚的不对称氧化是合成手性亚砜最有效的方法. 理性设计各种手性金属络合物催化剂应用于催化对映选择性氧化潜手性硫醚反应中, 近年来引起了化学家们较大的关注. 综述了各类手性金属络合物催化剂在硫醚不对称氧化中的应用.     

铜催化的立体选择性Doyle-Kirmse反应

以重氮化合物和烯丙基硫醚/炔丙基硫醚为反应底物,通过手性辅基和大位阻配体的不对称双诱导策略,高对映选择性地实现了经由铜卡宾产生硫叶立德的不对称[2,3]-σ重排反应(Doyle-Kirmse反应).脱除手性辅基后反应最高可以得到96%ee对映选择性.机理探究实验表明,反应很可能经历了自由的叶立德重排过程.该反应被进一步应用到含手性中心烯丙基硫醚的动力学拆分中.     

手性亚砜合成

手性亚砜及其衍生物广泛作为重要手性中间体和辅剂、手性配体和催化剂、手性药物。手性亚砜可以采用生物方法和化学方法来合成,化学方法包括手性辅剂诱导、手性氧化剂氧化、手性拆分和不对称催化等。本文简要综述了手性亚砜的各种用途和各种合成方法的研究进展,主要介绍了钛和钒催化的不对称硫醚氧化反应,也介绍了作者最近在钒催化的不对称硫醚氧化反应方面所做的研究工作。     

手性铁催化体系在不对称催化中的应用研究

本文介绍了手性铁催化体系在酮及亚胺的不对称还原、烯烃及硫醚的不对称氧化、不对称环加成、不对称环丙烷化以及不对称Friedel-Crafts烷基化等反应中的应用.     

埃索美拉唑钠的合成

以不对称氧化反应合成埃索美拉唑钠,优化合成工艺路线。首先制备奥美拉唑硫醚,硫醚再氧化生成埃索美拉唑,最后与氢氧化钠反应制备埃索美拉唑钠。总收率达57.2%,目标化合物的结构经IR、1H NMR和MS的确证。     

手性钛配合物催化不对称反应研究

手性钛配合物是一类很有用的手性催化剂,在许多反应中显示出了良好的催化活性和高的对映选择性。在我们研究的系列反应中,发现手性钛配合物是一类优良的手性催化剂,其中不对称催化杂Diels-Alder反应制备二氢吡喃酮(99%ee),不对称催化硫醚氧化成亚砜反应(96%ee)和不对称催化硅腈化反应(87%ee),都获得了好的催化活性和高的对映选择性。我们对以上反应中其催化剂的用量、溶剂、催化剂浓度和抗衡离子的Lewis酸碱性、底物的结构与对映选择性的关系、催化循环机理等进行了较系统、深入的研究,发现非共价相互作用和分子识别现象在不对称催化反应中显示出重要的作用,为进一步设计新的手性催化剂,发展不对称催化反应提供了基础数据。     

钠型离子交换树脂催化过氧化氢选择性氧化硫醚的研究

在以钠型强酸性离子交换树脂为催化剂和过氧化氢为氧化剂的反应条件下,首次研究了选择性氧化苯甲硫醚生成苯甲亚砜的反应,优化得到了合成苯甲亚砜的最佳合成条件为:反应底物苯甲硫醚8mmol、过氧化氢9.6mmol、反应溶剂甲醇10mL、反应温度为常温、反应时间为8h、催化剂用量为底物摩尔量的50%。此反应的转化率大于90.0%,选择性大于99.9%。催化剂重复使用15次未见其活性和选择性明显下降。在类似的反应条件下,其他5种硫醚也被高效和高选择性地氧化为相应的亚砜。     

无催化条件下采用叔丁基过氧化氢(TBHP)选择性氧化硫醚/二硫醚至亚砜/单砜（英文）

在常见氧化剂叔丁基过氧化氢(TBHP)的存在下,成功开发了一种选择性将硫醚氧化成亚砜,将二硫醚氧化成单砜的新方法,得到一系列亚砜和单砜类化合物,收率为67%～98%.该方法具有不使用任何催化剂和添加剂、底物适用性广、反应效率高、选择性好等优点.此外,通过控制实验,提出了一种合理的自由基反应机理.     

β-环糊精衍生物诱导Na2MoO4催化H2O2不对称氧化苯甲硫醚

以单(6-O-p-甲苯磺酰基)-β-环糊精为原料,通过亲核取代反应合成了5个未见文献报道的环状氨基醇修饰β-环糊精CD-1～CD-5,收率36%～68%,其结构经过1H NMR,13C NMR和ESI-MS进行表征确认.将这些β-环糊精衍生物CD-1～CD-5作为Na2MoO4的配体,应用于H2O2不对称氧化苯甲硫醚,研究结果显示,反应介质的pH值对该反应体系的对映选择性具有较大影响.较佳配体CD-4在pH 7.0,1 mol/L CH3COONa-HCl中,诱导Na2MoO4催化H2O2不对称氧化苯甲硫醚,ee值为21.25%.通过2D-1H ROESY NMR表征,表明制约CD-1～CD-5在诱导Na2MoO4催化H2O2不对称氧化苯甲硫醚反应中ee值提高的主要因素为CD-1～CD-5的分子内自包结行为,并且该自包结状态也从量子化学计算方面得到了证实.     

系列手性二齿配体在硫醚的不对称氧化反应中的应用

设计合成了系列手性二齿配体,并将它们与Ti(OPr-i)4生成的配合物用于催化硫醚的不对称氧化,考察了配体的结构对反应活性和对映选择性的影响,阐明了手性配体的构型与产物亚砜过量异构体构型间的关系.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Exploring the scope of the Gewald reaction: Expansion to a four-component process

An efficient four-component reaction was developed to take advantage of the reactivity of the 2-aminothiophene-3-carbonitrile functionality, which is obtained during the classical three-component Gewald reaction. Various α-methylene bearing ketones were reacted with malononitrile, elemental sulfur, and aryl/heteroarylnitrile derivatives in t-BuOH/NaOH to afford 2-arylthieno[2,3-d]pyrimidin-4-amines in high yields. Preliminary studies revealed the photophysical properties of the products and their potential for use as metal sensors.