Unexpected Stereospecific Rearrangement-Addition Reaction of Trisubstituted Gibberellin Epoxides with Trimethylaluminium

The gibberellins (GAs) are diterpenoid plant growth hormones which are essential to the normal growth and development of plants1. Over one hundred GAs have been identified to date and most of these compounds are present in nature only in minute quantities. Based on their carbon skeleta, the known gibberellins can be classified into two major groups, i.e., C20-gibberellins (C20-GAs, e.g. GA12, GA53) which contain the full twenty diterpenoid carbon atoms and C19-gibberellins (C19-GAs, e.…     

Regioselective Opening Reaction of Epoxides with Diphenyl Diselenides

The oxirane ring opening[1] with various nuclephiles is an important synthetic transformation to allow easy ac cess to a large number of functionalized intermediates that are required during the synthesis of natural products. [2]The reaction of epoxides with phenylselenolate ion gave the organic selenides[3] which were formed via trans opening of the epoxides with the selenolate ion. However, many of methods suffer from lack of generality, poor regioselectivity and low temperature ( - 78 ℃ ). [4]     

Epoxides as Alkylating Reagents for the Catellani Reaction

We report a cooperative catalytic system comprising a Pd^II complex, XPhos, and the potassium salt of 5‐norbornene‐2‐carboxylic acid that enables the use of epoxides as alkylating reagents in the Catellani reaction, thereby expanding the existing paradigm of this powerful transformation. The potassium salt of inexpensive 5‐norbornene‐2‐carboxylic acid acts as both mediator and base in the process. This mild, chemoselective, scalable, and atom‐economical protocol is compatible with a wide variety of readily available functionalized aryl iodides and epoxides, as well as terminating olefins. The resulting products undergo facile oxa‐Michael addition to furnish ubiquitous isochroman scaffolds.     

三正丁基膦参与的二苯联硒与吖啶及环氧化合物的开环反应

Aziridines and epoxides were reacted with diphenyl diselenide in the presence of a stoichiometric amount of （n-Bu）3P, respectively, giving β-amino- or β-hydroxy selenides in moderate to excellent yields under mild conditions. In the reactions the （n-Bu）3P might act as a reductant though it was a nucleophilic catalyst in other similar ring-opening reactions.     

Reaction of Epoxides with (Alkylthio)methyl Chloride

The reaction of (methylthio)methylchloride with 1,2-epoxybutane and styrene oxide furnishes eleven and eight compounds, respectively. The probable mechanism of their formation and their mass spectral characterization are presented in this article.     

Cycloaddition Reaction of Epoxides with Various Alkenes Under Microwave Irradiation

Abstract

The reactivity of gem-dicyano epoxides with various alkenes is studies in solvent free conditions, and in homogeneous solution, under microwave irradiation. Microwave heating of these substrates in solvent, yields carbonyl ylides which give 1-3-dipolar cycloaddition.     

1,1,3,3-四(全氟己基乙基)二锡氧烷二聚体在环氧化合物开环反应中的催化作用

采用氟碳-有机溶剂两相催化体系,考察了1,1,3,3-四(全氟己基乙基)二锡氧烷二聚体(1)在环氧化合物开环反应中的催化作用.结果表明,催化剂(1)在氟碳-有机溶剂两相体系中使环氧苯乙烯和甲醇的开环反应产率高达95%,¹³CNMR谱表明,开环反应的区域选择性为100%.在氟碳-有机溶剂两相催化体系中以一锅法制备了3-苯基丙酸2-甲氧基-2-苯乙醇酯,收率高,方法简便,催化剂几乎可以定量回收循环使用.     

Visible-Light Mediated Arbuzov-Like Reaction with Thiophenols

We hereby disclose, a visible light mediated addition of sulfenyl radicals to trialkyl phosphites to access functionalized phosphorothioates. The use of cheap and readily available Eosin Y as a photocatalyst under mild energy efficient conditions bypassing the use of external oxidants forms the chief highlight of the work. The protocol is scalable and mechanistic studies indicate that the reaction proceeds through an ionic-Arbuzov like pathway from phosphoranyl radicals.     

The Aqueous Trimethylamine Mediated Baylis-Hillman Reaction

Aqueous trimethylamine mediated Baylis-Hillman coupling of alkyl acrylates with aldehydes is described.     

双功能金属卟啉催化环氧化合物与 CO2 偶联反应合成环碳酸酯

 合成了新颖的双功能水溶性金属卟啉 催化剂 M(TTMAPP)I4(X) (M = Co, Fe, Mn 和 Cr; X = OAc, CF3COO, CCl3COO, OTs, Cl, Br 和 I), 研究了它们催化 CO2 与末端环氧化合物合成环碳酸酯的偶联反应. 分别考察了反应温度、不同金属的 Lewis 酸中心、抗衡离子和催化剂重复使用次数对反应性能的影响. 当以 Co(III)(TTMAPP)I4(OAc) 为催化剂, 底物与催化剂摩尔比为 1 000, 温度为 353 K, CO2 压力为 667 kPa 和无溶剂条件下, 反应 5 h 时丙烯环碳酸酯收率为 95.4%. 在 298 K, 底物与催化剂之比为 2 000 时, 加入 1 ml 甲醇, 反应 24 h 丙烯环碳酸酯收率为 19.4%. 催化剂可以用乙醚回收, 循环使用 5 次后催化剂活性没有明显降低.     

Reaction in Low Hydrated Solid-Liquid Heterogeneous Medium: Thiiranes Synthesis from Epoxides

A new method for the selective thiiranes synthesis from epoxides has been elaborated. A low hydrated solid-liquid heterogeneous medium is involved which contains solid thiocyanate with or without solvent.     

Catalytic Three‐Component Domino Reaction for the Preparation of Trisubstituted Oxazoles

Multicomponent reactions are attractive for assembling functionalized heterocyclic compounds. To this end, an efficient gold‐catalyzed three‐component domino reaction to form oxazoles directly from imines, alkynes, and acid chlorides is presented. The reaction proceeds in a single synthetic step by using a gold(III)–N,N′‐ethylenebis(salicylimine) (salen) catalyst to give trisubstituted oxazoles in up to 96 % yield. The substrate scope, a mechanistic study exploring the role of the gold catalyst, and the synthetic applications of the oxazole products are discussed.     

Sultones and Sultines via a Julia–Kocienski Reaction of Epoxides

The development of the homologous Julia–Kocienski reaction has led to the discovery of two new reaction modes of epoxides with sulfones. These pathways allow rapid and direct access to a range of γ‐sultones and γ‐sultines.     

各种金属参与的水相Barbier-Type反应

详细地概括了各种金属和金属盐参与的水相Barbier-Type反应,对反应机理以及反应的化学、区域和立体选择性进行了系统的总结,此外,还对水相Barbier-Type反应在有机合成中的应用作了初步的介绍.     

An Aldol-Like Reaction Mediated by SmI2

α-Haloketone reacted with aldehydes to form α, β-unsaturated ketones accompanied by dehalogenation in the presence of SmI₂. Mechanism involving samarium enolate intermediate formed in situ from α-haloketone with both SmI₂ and Sm(III)/I species was proposed.