Regiochemical and stereochemical studies on halocyclization reactions of unsaturated sulfides
摘要:
The regiochemistry and stereochemistry for the halocyclization reactions of unsaturated benzyl sulfides have been examined as a function of tether length, type of unsaturation (carbon-carbon double bond versus carbon-carbon triple bond), substituents, and halogenating agent. Alkenyl sulfides were found to react with iodine or bromine at room temperature to give five-membered ring cycloadducts exclusively over those having four-membered rings, while for larger systems, six-membered ring products are formed preferentially over their five-membered ring isomers and exclusively over the seven-membered ring adducts. The endo- versus exo-regioselectivity of these alkenyl sulfide ring closures most likely reflects the difference in thermodynamic stabilities of the beta-halo sulfide cycloadducts, which are able to equilibrate via a common episulfonium intermediate. The efficiency of the cyclization process markedly drops off for these alkenyl sulfides as the tether length increases beyond four intervening carbon centers. Thus, while the halogenations of 3-butenyl sulfides and 4-pentenyl sulfides give high yields of cycloadducts, those of 5-hexenyl sulfides afford only small amounts of cyclized products and large quantities of acyclic dibromides. Conversely the reactions of acetylenic sulfides with iodine give uniformly high yields and regiochemical control regardless of the tether length. Thus, 3-butynyl and 4-pentynyl sulfides cyclize cleanly to the five-membered ring while 5-hexynyl sulfides give exclusively the six-membered ring, The products arising from these alkynyl sulfide ring closures are believed to be formed under kinetic control. The methodology has been applied to the synthesis of unusual bicyclic beta-lactams related to the penicillin family of antibiotics.
Dihydroxylation and oxidative cleavage of olefins in the presence of sulfur
作者:Tarek Sammakia、T.Brian Hurley、Douglas M. Sammond、Randall S. Smith、Susan B. Sobolov、Thomas R. Oeschger
DOI:10.1016/0040-4039(96)00879-9
日期:1996.6
The dihydroxylation of olefins using AD-mix or in the presence of sulfides has been examined as has the rate of oxidation of various classes of sulfides. The selectivity of olefinoxidation in preference to sulfur oxidation depends on the nature of the sulfur moiety, and can be problematic for certain classes of substrates.
Photocatalytic Activation of Elemental Sulfur Enables a Chemoselective Three-Component Thioesterification
作者:Sho Murakami、Takeshi Nanjo、Yoshiji Takemoto
DOI:10.1021/acs.orglett.1c02904
日期:2021.10.1
thioesterification using olefins, α-ketoacids, and elemental sulfur has been developed. The photocatalytic activation of elemental sulfur, a cheap and abundant sulfursource, enables the rapid installation of a sulfur atom into molecules, reactions that ordinarily would require the use of reactive and malodorous sulfur-containingcompounds such as thiols and thioacids. This novel reaction is characterized
已经开发出使用烯烃、α-酮酸和元素硫的温和且化学选择性的三组分硫酯化反应。元素硫的光催化活化是一种廉价且丰富的硫源,能够将硫原子快速安装到分子中,而这些反应通常需要使用反应性和恶臭的含硫化合物,如硫醇和硫代酸。这种新反应的特点是产量高,底物范围广,可以将硫酯部分引入复杂的分子中,包括类固醇、肽和未受保护的糖苷。机理研究表明,这种转变的成功取决于元素硫所发挥的多种作用,包括硫化剂、末端氧化剂和 HAT 介质。
One-pot thiol-free synthetic approach to sulfides, and sulfoxides selectively
direct synthesis of sulfides and sulfoxides under green conditions without using any metal catalyst is reported. For this purpose, we used benzyl bromides as starting materials in the presence of potassium thioacetate (PTA) and Oxone® which are low-cost, and readily accessible chemicals. This method is highly compatible with a variety of functional groups and delivered a series of sulfides, bis-sulfides
Ruthenium-catalyzed intermolecular alkene–alkyne couplings in biologically relevant media
作者:Alejandro Gutiérrez-González、Daniel Marcos-Atanes、Leonard G. Cool、Fernando López、José L. Mascareñas
DOI:10.1039/d3sc01254a
日期:——
cyclopentadienyl Ru(II) catalysts can efficiently promote mild intermolecular alkyne–alkene couplings in aqueous media, even in the presence of different biomolecular components, and in complex media like DMEM. The method can also be used for the derivatization of amino acids and peptides, therefore proposing a new way to label biomolecules with external tags. This C–C bond-formingreaction, based on simple alkene
阳离子环戊二烯基 Ru( II ) 催化剂可以有效促进水介质中温和的分子间炔烃-烯烃偶联,甚至在存在不同生物分子组分的情况下,以及在 DMEM 等复杂介质中也是如此。该方法还可用于氨基酸和肽的衍生化,从而提出了一种用外部标签标记生物分子的新方法。这种基于简单烯烃和炔烃反应物的 C-C 键形成反应现在可以添加到过渡金属催化剂促进的生物正交反应的工具箱中。
Rh(III)-Catalyzed Diastereo- and Enantioselective Regiodivergent (Hetero)Arylamidation of (Homo)Allylic Sulfides
rhodium-catalyzed 3-component conjunctive diastereo- and regioselective arylamidation of (homo)allylic sulfides, organon boronic acids, and dioxazolones is reported. These reactions deliver the 1,2-insertion and 2,1-insertion arylamidation products, respectively, for allylic sulfides and homoallylic sulfides. The enantioselective arylamidation of terminal and internal allylic sulfides is achieved, furnishing