碘催化烯烃双官能团化反应制备β-羟基硫醚

室温下,以碘单质为催化剂,以空气为氧化剂,以乙腈水溶液为反应溶剂, 烯烃和硫代磺酸酯反应生成β-羟基硫醚化合物3a~3x（3i, 3k, 3r, 3s为新化合物）,采用¹H NMR,¹³C NMR,MS(ESI)和元素分析对其结构进行确证。以S-(4-氯苯基)-4-氯硫代苯磺酸酯(1)和苯乙烯(2)的反应为模板,对反应条件进行优化。结果表明：最佳反应条件为：S-(4-氯苯基)-4-氯硫代苯磺酸酯 0.5 mmol,苯乙烯1 mmol,催化剂碘用量为0.1 mmol,乙腈1.5 mL,去离子水0.5 mL,室温下反应2 h,收率可达82%。     

合成抗病毒母体三羟基核苷的新方法

三羟基核苷因其具有良好的抗病毒性能及作为核酸代谢作用的抑制剂而受到人们的关注．文献报道的合成方法［１～３］因反应需避光，温度控制要求严格，中间体二醛不稳定［４］，给操作带来困难．产物不易纯化，一般局限于使用离子交换色谱法［５］，而按此方法得到的无环核...     

烯烃的催化不对称氨羟基化反应

烯烃的催化不对称氨羟基化反应是Ｓｈａｒｐｌｅｓｓ继手性钛络合物催化的烯丙醇的不对称环氧化反应和烯烃的催化不对称双羟基化反应这后发现的又一极为重要的催化不对称反应。本文对这一新反应作一综述。     

一种新型的烯烃邻羟基乙酰氧基化反应

烯烃有多种氧化方式,依试剂和反应条件的不同,可被转化为各种相应的产物。最近,Truesdale等报道,在铋酸钠和乙酸的存在下,烯烃可以直接被氧化为相应的邻羟基乙酸酯,但产率较低(10～40％),反应时间亦较长(3～24h)。Morimoto等以乙酸钴对芳基烯烃进行氧化,     

樟脑衍生的β-羟基酮的不对称合成

不对称合成方法学及其应用是现代合成化学的基石之一,也是当代有机化学及其相关学科研究的热点和前沿。在不对称合成越来越重要的今天,手性试剂的作用已是最为重要和必不可少的反应试剂。价廉易得的天然樟脑作为天然手性源,在不对称合成领域中一直备受关注[1,2,3,4],其可用于合     

过渡金属催化的6-苯基-5,6-二氢-2H-吡喃-2-酮的合成——推荐一个大学有机化学综合实验

有机合成中,碳-碳键的形成和断裂是一个永恒的热门话题,科学家为此发展了很多形成碳-碳键的方法。在这一领域,诞生了不少诺贝尔化学奖的成果,格氏反应和烯烃复分解反应就是其中的经典案例。烯烃复分解反应提供了一种连接sp2-碳和sp2-碳的全新思路,发展出了一些活性分子全合成的高效路径。因而,2005年的诺贝尔化学奖授予了对烯烃复分解反应有杰出贡献的三位科学家。本有机化学综合实验由三个反应构成,包括改进的格氏反应、DMAP催化的酯化反应和关环烯烃复分解反应。每一个反应都可独立成为一个基础有机化学实验,三步的连续反应可以作为一个综合多步合成实验。本实验有助于理解有机合成的过程和机理,体验有机合成的魅力。     

对羟基苯乙酮的合成

以苯酚和乙酐为原料，经过酯化反应和Fries重排反应合成了对羟基苯乙酮，收率58．5％，纯度98．68％。     

乙酰衍生化气相色谱-电子捕获检测法分析尿中α-羟基三唑仑和α-羟基阿普唑仑

三唑仑和阿普唑仑是目前国内麻醉抢劫案件中最常使用的两种麻醉药物。为确定案件性质及取得证据等原因,案件发生后常需要进行受害人血、尿等体液中药物或其代谢物的分析。这两种药物作用强、剂量小,服药后血中药物及其代谢物的浓度都很低,尿中药物的浓度也很低。相对而言,尿中代谢物α-羟基三唑仑(α-hydroxytrizolam,简写为α-     

光诱导醇的直接脱羟基衍生化研究进展

由于C_sp3—O键键能大的特点,传统还原裂解醇类的方法多涉及间接的活化过程,在温和条件下对醇C_sp3—O键直接裂解是一个巨大的挑战.近年来通过光诱导条件直接对其裂解进行脱羟基还原、脱羟基衍生化的策略取得了重大的突破,这些策略相较于传统方法不需要预活化步骤,也能避免传统当量氧化还原剂的使用,具有更好的原子经济性、步骤经济性以及氧化还原经济性.该主题综述文献较少,在此重点综述了光诱导下醇C_sp3—O键直接裂解还原及衍生化的进展,从而进一步推动该领域的蓬勃发展.     

5-溴-2-羟基苯甲醇的不对称羟基保护

采用分步法对5-溴-2-羟基苯甲醇中的不对称羟基进行了选择性保护.以2,3-二氢吡喃和氯甲醚为保护基,经两步反应得5-溴-2-甲醚氧基苯甲-2-(四氢吡喃)醚,其结构经1H NMR, IR和MS表征.     

Total Synthesis of Mycalolides A and B through Olefin Metathesis

An asymmetric total synthesis of the trisoxazole marine macrolides mycalolides A and B is described. This synthesis involves the convergent assembly of highly functionalized C1–C19 trisoxazole and C20–C35 side‐chain segments through the use of olefin metathesis and esterification as well as Julia–Kocienski olefination and enamide formation as key steps.     

Synthesis of 2,6-dioxabicyclo[3.3.0]octenes by tandem ring-rearrangement/cross metathesis

A facile synthesis of stereodefined 2,6-dioxabicyclo[3.3.0]octene derivatives from the vinyl ether of endo-7-oxanorbornen-2-ol via tandem ring-opening/ring-closing(ring-rearrangement)/cross metathesis is reported.     

Role of CO2 in dehydrogenation of propane over CrOX/SiO2 catalyst with low Cr content

When ethene alone was contacted with silica supported cobalt catalyst (Co/SiO₂), ethene homologation took place with considerable activity. Moreover, the propene metathesis reaction was suppressed ca. 1/6 fold as much as in the case using MoO_X/SiO₂ catalyst. The possibility of selective homologation with a lower activity for metathesis was suggested for the cobalt-based catalyst system.     

Template synthesis of a huge macrocycle by olefin metathesis using easily accessible [Pt(PEt(3))(2)] templates

We have reported the template synthesis of a 90-membered macrocycle by olefin metathesis. The macrocycle 7 was prepared by an initial six-oxidative-addition reaction of 2 by [Pt(PEt(3))(4)]. The definite structure of a six-oxidative product was confirmed by the crystal structure. The coordination of 2,6-bis(hex-5-enyloxy)pyridine to 3 led to the hexacationic aryl complex of type 4. The metathesis of olefin-substituted pyridine with Grubbs catalyst ([PhCH==RuCl(2)(Cy(3)P)(2)]) formed the expected macrocycle 5. The olefin metathesis reaction was formed under high dilution to suppress intermolecular olefin metathesis polymerization. The detachment of the newly formed macrocycle 6, followed by reduction to alkane macrocycle 7 by using palladium on charcoal and hydrogen led to a huge macrocycle. The mild and easy access of the template protocol opens a host of potential subsequent transformations toward the construction of a variety of macrocycles.     

Acyclic diene metathesis (ADMET) depolymerization: Ethenolysis of 1,4-polybutadiene using a ruthenium complex

α,ω-Vinyl-terminated butadiene oligomers can be generated through the cross-metathesis of ethylene and high molecular weight 1,4-polybutadiene catalyzed by the complex RuCl₂(CHPh)(PCy₃)₂. The effect of varied ethylene pressure is studied in order to obtain the highest conversion to the monomer 1,5-hexadiene. A dramatic increase in yield of this monomeric diene is realized relative to previous published attempts utilizing a well-defined group VI metal alkylidene in the same chemistry. Traces of side products are observed, and alternate mechanisms for their formation were proposed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1857–1861, 1999     

The Total Synthesis of (−)‐Nitidasin

Nitidasin is a pentacyclic sesterterpenoid with a rare 5‐8‐6‐5 carbon skeleton that was isolated from the Peruvian folk medicine “Hercampuri”. It belongs to a small class of sesterterpenoids that feature an isopropyl trans‐hydrindane moiety fused to a variety of other ring systems. As a first installment of our general approach toward these natural products, we report the total synthesis of the title compound. Our stereoselective, convergent route involves the addition of a complex alkenyl lithium compound to a trans‐hydrindanone, followed by chemoselective epoxidation, ring‐closing olefin metathesis, and redox adjustment.     

Total Synthesis of Principinol B

We have accomplished the first and asymmetric total synthesis of principinol B, a grayanoid possessing an oxabicyclo[3.2.1] architecture. A functionalized 5/7/6/5 tetracyclic intermediate was assembled in a convergent manner by a diastereoselective intermolecular aldol reaction and subsequent carbonyl–olefin metathesis of two enantiomerically enriched fragments. The oxabicyclo[3.2.1] architecture containing a 6,10-ether bridge was constructed by the Williamson ether synthesis.     

Enantioselective synthesis of [7]helicene: dramatic effects of olefin additives and aromatic solvents in asymmetric olefin metathesis

The asymmetric synthesis of [7]helicene was accomplished in good ee (80%) by kinetic resolution by means of asymmetric olefin metathesis. Three key factors contributed to the success of the kinetic resolution: the use of new Ru-based olefin metathesis catalysts bearing C1-symmetric N-heterocyclic carbene ligands, simple olefins as additives to control the nature of the propagating alkylidene and hexafluorobenzene as a solvent.     

The stereoselective total synthesis of PF1163A

A stereoselective total synthesis of 13-membered macrocycle PF1163A, an antifungal agent, has been accomplished for the first time starting from d-xylose. This approach involves a diastereoselective allylation of lactal ether,^3a reductive ring opening of tetrahydrofuran ring,^3b asymmetric methylation reaction, Yamaguchi esterification, and ring closing metathesis as key steps.