Construction of Benzosiloles, Six- and Eight-Membered Silacyclic Skeletons, via a Pd-Catalyzed Intramolecular Mizoroki-Heck Reaction of Vinylsilanes

A variety of silacycles including benzosiloles, six- and eight-membered silacyclic skeletons, were efficiently synthesized via a Pd-catalyzed intramolecular Mizoroki-Heck reaction of vinylsilanes.     

Synthesis of Entacapone by Pd-Catalyzed Heck Coupling Reaction

Synthesis of entacapone from 4-iodo-2-methoxy-phenol with 2-cyano-N,N-diethylacrylamide by palladium-catalyzed Heck reaction, as a key step, is described.     

Nucleophilic Additions to Coordinated 1,10‐Phenanthroline: Intramolecular,Intermolecular, Reversible,and Irreversible

KN(SiMe₃)₂ reacts with [Re(CO)₃(phen)(PMe₃)]OTf via reversible addition to the phen ligand and irreversible deprotonation of the PMe₃ ligand followed by intramolecular attack to phen by the deprotonated phosphane, whereas MeLi irreversibly adds to phen. The addition of MeLi has been shown to be intermolecular, unlike previously known nucleophilic additions to pyridines.     

Intermolecular Cross-Acyloin Reactions by Fluoride-Promoted Additions of O-Silyl Thiazolium Carbinols

The addition of acyl anion equivalents to aliphatic aldehydes (crossed-acyloin reaction) has been developed. Cesium fluoride with isopropanol as solvent promotes the addition of O-silyl thiazolium carbinols to various aliphatic aldehydes in moderate to good yields. These reactions represent a general procedure for the selective coupling of aliphatic aldehydes by an acyl anion reaction which have been problematic until now.     

含分子内氢键的苯硫酚在水相中的Michael加成反应

苯硫酚的巯基是一个较强的亲核基团,对α,β-不饱和双键的Michael加成反应已有报道．但是当巯基的邻位存在与其形成氢键的基团时,如果按文献条件进行反应,或者反应无法进行,或者要使用反应条件苛刻的丁基锂,或者使用吡啶等毒性较大的反应溶剂,而且产率较低．本文选择     

无配体参与钯催化烯烃与芳基三烷氧基硅烷的交叉偶联反应

考察了钯催化下一系列烯烃化合物与不同芳基三烷氧基硅烷的反应,发展了一种新型无配体参与的Heck类型反应方法.研究表明:以Pd(OAc)2为催化剂,在K2CO3,n-Bu4NF 3H2O和AgOAc存在下,该Heck类型反应能够得到中等及优良的偶联产率,并且表现出较高的区域选择性和立体选择性.根据实验结果以及相关文献,对该Heck类型偶联反应的可能机理进行了探讨.     

Stereospecific Redox Reaction Directed by a Sulfinyl Group

Stereochemistry of reductions of a pyridinium and quinoliniums with an asymmetric sulfinyl group has been studied. Dithionite and borohydride prefer the face characterized by a lone pair on sulfur atom. Dihydropyridine prefers the face characterized by a S-O bond.     

Synthesis of Arylethylene or Diarylethylene Compounds by Pd-Catalyzed Heck Coupling Reaction

We have developed an effective palladium-catalyzed arylation or diarylation couplings of olefins with various aryl halides in the presence of readily available ligands. This method is simple, economical, and practical for the synthesis of arylethylene and diarylethylene.

Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for full experimental and spectral details.     

新型联苯类双膦配体的合成及钯催化Suzuki-Miyaura反应

以易得3-溴苯甲醚为原料经四步反应合成了新联苯双膦配体6,6'-二甲氧基-2,2'-二(二-2-吡啶基膦)-1,1'-联苯(DPP),且经氢谱、磷谱、碳谱和高分辨质谱表征.此配体的钯配合物对多种芳基溴和苯硼酸的Suzuki-Miyaura偶联反应表现出很高的催化性能,即使芳基溴有较大的空间位阻或者带有官能团取代基也能获得很好的结果.     

Facile Synthesis of a Stable Side-on Phosphinyne Complex by Redox Driven Intramolecular Cyclisation

Alkyne complexes with vicinal substitution by a Lewis acid and a Lewis base at the coordinated alkyne are prospective frustrated Lewis pairs exhibiting a particular mutual distance and, hence, a specific activation potential. In this contribution, investigations on the generation of a W^II alkyne complex bearing a phosphine as Lewis base and a carbenium group as Lewis acid are presented. Independently on potential substrates added, an intramolecular cyclisation product was always isolated. A subsequent deprotonation step led to an unprecedented side-on λ⁵-phosphinyne complex, which is interpreted as highly zwitterionic according to visible absorption spectroscopy supported by TD-DFT. Low-temperature ³¹P NMR and EPR spectroscopic measurements combined with time-dependent IR-spectroscopic monitoring provided insights in the mechanism of the cyclisation reaction. Decomposition of the multicomponent IR spectra by multivariate curve resolution and a kinetic hard-modelling approach allowed the derivation of kinetic parameters. Assignment of the individual IR spectra to potential intermediates was provided by DFT calculations.     

倍硫磷的甲基在分子内和分子间迁移的质谱研究

甲基迁移反应在合成化学和生命科学领域具有重要意义.迄今为止，所报道的甲基迁移反应大多数发生在不同种类分子之间.因此，寻找新型甲基迁移反应具有一定的研究价值.本研究以环境中常见的杀虫剂倍硫磷为研究对象，采用电喷雾质谱技术为分析工具对反应体系进行高灵敏分析，探究在CF₃COOH及纳米二氧化钛（TiO₂）条件下，倍硫磷分子中发生甲基迁移反应的可能性.结果表明，在CF₃COOH和TiO₂共同作用下，倍硫磷分子中的甲基可以从同一分子的氧原子上迁移到不饱和硫原子上，发生分子内1，3-甲基迁移反应，形成异构体硫甲基化产物；同时，异构体产物中的甲基还可以从硫原子上再继续迁移到另一分子倍硫磷的不饱和硫原子上，发生分子间甲基迁移反应.同时结合密度泛函理论计算对倍硫磷分子内和分子间甲基迁移反应的过程进行动态模拟，并对其迁移机理进行解释.本研究发现了倍硫磷能发生分子内和分子间甲基迁移反应，提供了一种研究甲基迁移反应的质谱方法，为倍硫磷的降解研究提供了新思路.     

Difunctionalization of Alkenes and Alkynes via Intermolecular Radical and Nucleophilic Additions

Popular and readily available alkenes and alkynes are good substrates for the preparation of functionalized molecules through radical and/or ionic addition reactions. Difunctionalization is a topic of current interest due to its high efficiency, substrate versatility, and operational simplicity. Presented in this article are radical addition followed by oxidation and nucleophilic addition reactions for difunctionalization of alkenes or alkynes. The difunctionalization could be accomplished through 1,2-addition (vicinal) and 1,n-addition (distal or remote) if H-atom or group-transfer is involved in the reaction process. A wide range of moieties, such as alkyl (R), perfluoroalkyl (R_f), aryl (Ar), hydroxy (OH), alkoxy (OR), acetatic (O₂CR), halogenic (X), amino (NR₂), azido (N₃), cyano (CN), as well as sulfur- and phosphorous-containing groups can be incorporated through the difunctionalization reactions. Radicals generated from peroxides or single electron transfer (SET) agents, under photoredox or electrochemical reactions are employed for the reactions.     

Design and Synthesis of Bis-thioureas Ligands for Pd-Catalyzed Heck Reaction

The palladium-catalyzed arylation of olefins (the Heck reaction) is one of the most versatile tools for C-C bond formation in organic synthesis. Phosphine ligands are generally used to stabilize the reactive palladium intermediates, the air-sensitivity of phosphine ligands, however, places significant limits on their synthetic applications. Recently, Yang1 and we2 have reported Heck and Suzuki reactions of highly active arenediazonium salts and halides catalyzed by air-stable monothiourea-Pd…     

Synthesis of a Dimeric Magnesium(I) Compound by an MgI/MgII Redox Reaction

The synthesis of dimeric magnesium(I) compounds of the general type RMgMgR (R=monoanionic substituent) is still a challenging synthetic task and limited to few examples with sterically demanding ligands with delocalized CN‐frameworks that all have been accessed by Na or K metal reduction of magnesium(II) halide precursors. Here we report on the synthesis of a novel diiminophosphinato magnesium(I) compound that has been synthesized by a facile redox reaction using a known magnesium(I) complex. The synthetic strategy may be applicable to other ligand systems and can help expand the class of low oxidation state magnesium complexes even if reductions with Na or K are unsuccessful. The new dimeric magnesium(I) complex has been structurally characterized and undergoes a C? C coupling reaction with tert‐butylisocyanate.     

The Photoredox‐Catalyzed Meerwein Addition Reaction: Intermolecular Amino‐Arylation of Alkenes

A variety of amides are efficiently accessible under mild conditions by intermolecular amino‐arylation using a photo Meerwein addition with visible light. The reaction has a broad substrate scope, tolerates a large range of functional groups, and was applied to the synthesis of a 3‐aryl‐3,4‐dihydroisoquinoline.     

Synthesis of Antitumor Lycorines by Intramolecular Diels-Alder Reaction

Pharmacologically interesting lycorines were obtained by a short, efficient method based on an intramolecular Diels-Alder reaction between an alpha-pyrone and an alkyne, followed by loss of CO(2) in a retro Diels-Alder reaction. The cyclization precursors (pyrones 9) were obtained in good yields in two or three steps from the corresponding homophthalic acid or anhydride.