A New Method of Generation of .alpha.-Selenocarbenium Ions from Se,O-Heteroacetals and Their Reactions
摘要:
Various Se,O-heteroacetals were prepared by the LiAlH4 reduction of diselenides 1 followed by alkylation with methoxymethyl chloride or (2-methoxyethoxy)methyl (MEM) chloride. Olefinic and acetylenic alpha-seleno carbenium ions were generated by the selective C-O bond cleavage of O-(2-methoxyethyl)-Se,O-heteroacetals with titanium(IV) chloride and cyclized to give the seleno heterocyclic compounds. Olefinic MEM-selenides 3a,b,d-f,h underwent the endo-mode cyclization to afford 4-chloroselenacycloalkanes 4a,b,d-f,h in good yields, whereas acetylenic MEM-selenides 12b-e,g-j underwent the exo-mode cyclization to give 3-(1-chloroalkylidene)selenacycloalkanes 13b-e,g-j. This new utilization of alpha-seleno carbenium ions was also applied to the intramolecular and intermolecular Friedel-Crafts reactions.
An intermolecular aminoselenation of alkenes with sulfonimides and diselenides is achieved via a visible-light-induced three component reaction. A broad variety of aminoselenation products is accessible in good yields with excellent functional group compatibility. Additional features of this new protocol include being additive- and photocatalyst-free and the use of natural sunlight as well as suitability
A transition-metal-free synthetic method has been developed for the synthesis of unsymmetrical diaryl chalcogenides (S, Se, and Te) from diaryl dichalcogenides and arenes under oxidative conditions by using potassium persulfate at room temperature. Variously substituted arenes such as anisole, thioanisole, diphenyl ether, phenol, naphthol, di- and trimethoxy benzenes, xylene, mesitylene, N,N-dimethylaniline
已开发出一种无过渡金属的合成方法,该方法用于在室温条件下通过使用过硫酸钾,在氧化条件下由二芳基二卤化锑和芳烃合成不对称的二芳基硫属元素化物(S,Se和Te)。各种取代的芳烃,例如苯甲醚,硫代苯甲醚,二苯醚,苯酚,萘酚,二和三甲氧基苯,二甲苯,均三甲苯,N,N-二甲基苯胺,溴取代的芳烃,萘和二芳基二卤化碳经历了碳硫族键形成反应在三氟乙酸中生成不对称的二芳基硫属元素化物。为了理解反应的机理部分,由77进行了详细的中间体原位表征通过使用二苯基二硒化物为底物进行Se NMR光谱分析。77 Se NMR研究表明,亲电子物质ArE +是由二芳基二卤化二硫化物与过硫酸盐在三氟乙酸中反应生成的。芳基硫属元素离子对芳烃的亲电攻击可能是芳基-硫属元素键形成的原因。
Transition Metal-Catalyzed Synthesis of (E)-2-(Alkylthio)alka-1,3-dienes from Allenes and Dialkyl Disulfides with Concomitant Hydride Transfer
Reaction of dialkyldisulfides or diselenides with allenes is catalyzed by a rhodium-phosphine complex and trifluoromethanesulfonic acid giving (E)-2-alkylthio(seleno)-1,3-dienes and (E)-2-alkylthio(seleno)-2-alkenes. Unlike the reaction of alkynes, the reaction of allene is accompanied by hydridetransfer.
Efficient Reductive Selenation of Aromatic Aldehydes to Symmetrical Diselenides with Se/CO/H<sub>2</sub>O under Atmospheric Pressure
作者:Fengshou Tian、Zhengkun Yu、Shiwei Lu
DOI:10.1021/jo049733i
日期:2004.6.1
An efficient method for the synthesis of symmetrical diselenides is described. Reductive selenation of aromatic and heterocyclic aromatic aldehydes (ArCHO) with Se/CO/H2O in DMF afforded diselenides (ArCH2SeSeCH2Ar) in yields up to 94% underatmosphericpressure without use of a base.
描述了合成对称二硒化物的有效方法。在大气压下,不使用碱,在DMF中用Se / CO / H 2 O对芳香族和杂环芳香族醛(ArCHO)进行还原硒化,可得到产率高达94%的二硒化物(ArCH 2 SeSeCH 2 Ar)。
Flash Pyrolysis of Selenides. Syntheses of Bibenzyls, Olefins, and Related Compounds
bibenzyls and related ethane derivatives in high yields. Other diselenides were easily caused to cleave to give various aromatic and aliphatic olefins in good yields together with elemental selenium. Lepidopterene, [2.2]paracyclophane, and benzocyclobutene were prepared by thermal cleavage of their corresponding phenylselenomethyl-substituted compounds as an application of the pyrolysis concerned.