Reaction of magnesium alkylidene carbenoids with lithium acetylides and lithium thiolates: a novel synthesis of conjugated enynes and vinyl sulfides

Magnesium alkylidene carbenoids were generated from 1-chlorovinyl p-tolyl sulfoxides with i-PrMgCl at −78 °C in THF or toluene via the sulfoxide-magnesium exchange reaction. Reaction of the generated magnesium alkylidene carbenoids with lithium acetylides or lithium thiolates gave conjugated enynes or vinyl sulfides, respectively, in moderate to good yields. The intermediate of this reaction was found to be the alkenyl anion and it could be trapped with some electrophiles to give tetra-substituted conjugated enynes and vinyl sulfides.     

Protected ester,nitrile, carbinol and carbinyl amine cyclopropanone hydrates

Methyl diazoacetate reacted with the ketene acetal I in the presence of dirhodium tetraacetate yielding the metastable cyclopropanone ketal ester II, which was converted to the primary and tertiary cyclopropyl carbinols III and IV by treatment with lithium aluminum hydride and methyl lithium, respectively. Diazoacetonitrile yielded a stable crystalline cyclopropanone ketal nitrile X following reaction with the ketene acetal I.     

Synthesis of Cyclopropyl Ethers and Cyclopropanols by Carbene Transfer – Acetolysis of Cyclopropyl p-Toluenesulfonates

The reaction of chloromethyl phenyl ether with butyllithium in olefins yields phenoxy-cyclopropanes. 1-Chloro-1-phenoxycyclopropanes can be prepared in a similar manner, though the yields are poor. Alkoxycyclopropanes are formed when dichloromethyl alkyl ethers are treated with methyllithium/lithium iodide in the presence of olefins. Cyclopropanols can be obtained in good yields by reaction of (β-chloroethoxy)cyclopropanes either with butyl- or ethyllithium or with bases. – As was shown by acetolysis experiments with cyclopropyl p-toluenesulfonates having a known steric configuration, the rearrangement of a cyclopropyl derivative into an allyl cation proceeds in accordance with the Woodward-Hoffmann-DePuy rule. The solvolysis of exo-bicyclo[n.1.0]alkyl p-toluene-sulfonates is assumed to proceed via “semi-open” intermediates, which are somewhere between an allyl cation and a cyclopropyl cation.     

A new method of olefin synthesis. Coupling of lithium dialkylcuprates with enol triflates

Enol trifluoromethansulfonates react with lithium dialkylcuprates to give the coupling products in high yields. The reaction is stereoselective and is successful with a wide variety of organocuprates, including methyl, butyl, phenyl, vinyl, and cyclopropyl reagents.     

The application of nanostructured transition metal sulfides as anodes for lithium ion batteries

With wide application of electric vehicles and large-scale in energy storage systems, the requirement of secondary batteries with higher power density and better safety gets urgent. Owing to the merits of high theoretical capacity, relatively low cost and suitable discharge voltage, much attention has been paid to the transition metal sulfides. Recently, a large amount of research papers have reported about the application of transition metal sulfides in lithium ion batteries. However, the practical application of transition metal sulfides is still impeded by their fast capacity fading and poor rate performance. More well-focused researches should be operated towards the commercialization of transition metal sulfides in lithium ion batteries. In this review, recent development of using transition metal sulfides such as copper sulfides,molybdenum sulfides, cobalt sulfides, and iron sulfides as electrode materials for lithium ion batteries is presented. In addition, the electrochemical reaction mechanisms and synthetic strategy of transition metal sulfides are briefly summarized. The critical issues, challenges, and perspectives providing a further understanding of the associated electrochemical processes are also discussed.     

A simple one-pot synthesis of hydroxylated and carboxylated aryl alkyl sulfides from various bromobenzenes

A simple one-pot synthesis of aryl alkyl sulfides from various bromobenzenes containing a hydroxy, hydroxymethyl, hydroxyethyl, and carboxylic acid group at -o, -m, and -p positions is reported here. The reaction proceeds through, in sequence, in situ protection of the hydroxy or carboxylic acid group by reaction with a Grignard reagent, lithium-halogen exchange, the formation of lithium thiolates, and the nucleophilic attack of lithium thiolates on various electrophiles without isolation of the thiolates, in one vessel. This procedure required a very short reaction time (1-1.5 h) and gave the corresponding sulfides in 75-97% yields.     

Asymmetric Ring‐Opening of Cyclopropyl Ketones with Thiol,Alcohol, and Carboxylic Acid Nucleophiles Catalyzed by a Chiral N,N′‐Dioxide–Scandium(III) Complex

A highly efficient asymmetric ring‐opening reaction of cyclopropyl ketones with a broad range of thiols, alcohols and carboxylic acids has been first realized by using a chiral N,N′‐dioxide–scandium(III) complex as catalyst. The corresponding sulfides, ethers, and esters were obtained in up to 99 % yield and 95 % ee. This is also the first example of one catalytic system working for the ring‐opening reaction of donor–acceptor cyclopropanes with three different nucleophiles, let alone in an asymmetric version.     

Synthesis and properties of 1-methylthiopropargylammonium salts and their use as key precursors to sulfur-containing enediynes

1-methylthiopropargylammonium salts were synthesized in a highly efficient manner by reaction of alkynyl S,N-acetals with methyl triflate. Reactions of the 1-methylthiopropargylammonium salts with Grignard reagents gave propargyl sulfides or allenyl sulfides, whereas the reaction with organocopper reagents led to exclusive formation of allenyl sulfides regardless of the nature of substituents on the acetylenic carbon. The salts undergo self-dimerization reactions when treated with organolithium and lithium amide bases.     

Asymmetric Ring‐Opening of Cyclopropyl Ketones with Thiol,Alcohol, and Carboxylic Acid Nucleophiles Catalyzed by a Chiral N,N′‐Dioxide–Scandium(III) Complex

A highly efficient asymmetric ring‐opening reaction of cyclopropyl ketones with a broad range of thiols, alcohols and carboxylic acids has been first realized by using a chiral N,N′‐dioxide–scandium(III) complex as catalyst. The corresponding sulfides, ethers, and esters were obtained in up to 99 % yield and 95 % ee. This is also the first example of one catalytic system working for the ring‐opening reaction of donor–acceptor cyclopropanes with three different nucleophiles, let alone in an asymmetric version.     

Cyclopropyl halides. Electron transfer in the lithium aluminum hydride reduction of gemdibromo and monobromocyclopropanes.

The stereochemistry of reduction of mixtures of r-1-bromo-1-deuterio-c- and t-2-phenylcyclopropane and the cyclized products from 1,1-dibromo-2-(3-butenyl cyclopropane upon reduction with lithium aluminum hydride give evidence of a configurationally equilibrated cyclopropyl radical as a reaction intermediate.     

Tandem cyclopropanation with dibromomethane under Grignard conditions

Tertiary Grignard reagents and dibromomethane efficiently cyclopropanate allylic (and certain homoallylic) magnesium and lithium alcoholates at ambient temperature in ether solvents. Lithium (homo)allyl alcoholates are directly cyclopropanated with magnesium and CH2Br2 under Barbier conditions at higher temperatures. The reaction rates depend on the substitution pattern of the (homo)allylic alcoholates and on the counterion with lithium giving best results. Good to excellent syn-selectivities are obtained from alpha-substituted substrates, which are in accord with a staggered Houk model. In tandem reactions, cyclopropyl carbinols are obtained from allyloxylithium or -magnesium intermediates, generated in situ by alkylation of conjugated aldehydes, ketones, and esters as well as from allyl carboxylates or vinyloxiranes. Using this methodology, numerous fragrance ingredients and their precursors were efficiently converted to the corresponding cyclopropyl carbinols.     

Improved preparation and new reactions of β -(1-phenylthio) cyclopropyl enones

β-(1-Phenylthio)cyclopropyl enones can be conveniently prepared via reaction of the lithium salts of α-hydroxymethylene ketones with 1-lithio-1-phenylthiocyclopropane and are converted efficiently by treatment with aqueous acid to γ-keto cyclobutanones and less successfully by thermolysis to -γ-keto phenylthiocyclopentenes.     

Chemoselective synthesis of highly substituted 1,2-allenyl ketones, furans, and 2-alkynyl ketones from reaction of lithium selenolates with 1-(1-alkynyl)cyclopropyl ketones and electrophiles

A homo-Michael addition reaction of lithium selenolates with 1-(1-alkynyl)cyclopropyl ketones and the subsequent reaction with electrophiles such as PhSeBr, NFSI and NCS is reported. Based on the nature of electrophiles, this reaction may afford highly substituted 1,2-allenyl ketones or furans (E(+) = PhSe(+)) and 2-alkynyl ketones (E(+) = F(+), Cl(+), active halides) as the final products, respectively.     

Unexpected formation of (E)-4-alkene 1,3-diketones from the three-component reaction of lithium selenolates with 1-(1-alkynyl)cyclopropyl ketones and aldehydes

A novel three-component stereoselective synthesis of (E)-4-alkene 1,3-diketones from lithium selenolates, 1-(1-alkynyl)cyclopropyl ketones, and aldehydes is reported. This reaction afforded the products in moderate to good yields with the formation of a new C-Se single bond, a new C-C double bond, and a new C-O double bond.     

The molecular structures of methylcyclopropane,cyclopropylamine and cyclopropyl lithium

Ab initio calculations of double zeta quality have been carried out on methylcyclopropane, cyclopropylamine and cyclopropyl lithium. A complete geometry optimization was carried out on the lithium compound and a partial geometry optimization on the other two. A high level of reliability has been obtained in the determination of the difference between similar bond parameters, in particular the deviations from ring symmetry caused by interaction with the substituents. For cyclopropylamine, the dominant effect is a flow of electron density in the σ system from the ring to the amino group. The electron flow in cyclopropyl lithium is, of course, dominated by donation of electrons into the σ system of the ring, but there is also a significant back donation into the vacant p orbitais of the metal atom. There is a similar effect, but much smaller, in methylcyclopropane which can be explained in terms of hyperconjugation. A coherent picture of substituent effects on the asymmetry of the cyclopropyl ring is beginning to emerge.     

5,6-Trimethylenethiapyrylium and 5,6,7,8-tetrahydrothiochromylium salts

5,6-Trimethylenethiapyrylium salts have been obtained for the first time. 5,6-Trimethyleneγ-thiopyrans (or 5,6,7,8-tetrahydro-γ-thiochromenes), which belong to a previously unknown series of two-ring sulfides, are formed by reaction of the 5,6-trimethylenethiapyrylium salts (or 5,6,7,8-tetrahydrothiochromylium salts) with Grignard reagents and lithium aluminum hydride.     

Density function studies on the PtCl2‐catalyzed asymmetric cycloisomerization reaction of hydroxylated enynes

The PtCl₂‐catalyzed asymmetric cycloisomerization reaction of hydroxylated enynes was studied using density functional theory (DFT). All structures have been optimized completely at the B3LYP/6‐311G(d,p) level. As shown, the cycloisomerization reaction is exothermic. The cycloisomerization reaction mainly undergoes the formation of catalyst‐hydroxylated enzyme coordination, the asymmetric cyclopropyl platinum carbene, catalyst–cyclopropyl enol coordination, and catalyst–cyclopropyl ketone coordination. The chirality‐limiting step for the asymmetric cycloisomerization reaction is the formation of the asymmetric cyclopropyl platinum carbene, and the rate‐determining step for this reaction is the formation of the catalyst–cyclopropyl ketone coordination. The dominant products predicted theoretically are (R,S) ‐syn_5a, in agreement with the experiment. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006     

Reduction of Thiocarbonyl Compounds with Lithium Diisopropylamide

Treatment of 4,4‐disubstituted 2‐phenyl‐1,3‐thiazole‐5(4H)‐thiones with lithium diisopropylamide (LDA; LiNⁱPr₂) in THF at ?78° yielded the corresponding 1,3‐thiazole‐5(4H)‐thioles in moderate yields. Sequential treatment with LDA and MeI under the same conditions led to the 5‐methylsulfanyl derivatives. Similarly, reaction of some cycloalkanethiones as well as diaryl thioketones with LDA and MeI gave cycloalkyl methyl sulfides and diarylmethyl methyl sulfides, respectively. A reaction mechanism via H transfer from LDA to the thiocarbonyl C‐atom via a six‐membered transition state is proposed for this unprecedented reduction of the C?S bond.     

SYNTHESIS OF CHIRAL SULFOXIDES BY ASYMMETRIC OXIDATION

Abstract

The main chemical or enzymatic methods of asymmetric oxidation of sulfides are reviewed. A new approach to chiral sulfoxides is described, which uses tertiobutyl hydroperoxide in presence of a chiral titanium complex. The results obtained during the last two years are summarized. The best enantiomeric excess amounts to 95% in the case of formation of cyclopropyl phenyl sulfoxide.     

单分子断键反应的理论研究

利用微扰理论和对称性规则,得到了单分子断键反应中反应物结构、过渡态和所断键之间的关系．据此,对环丙基自由基及其正负离子的热开环反应和过氧化氢基态均裂反应作出预言,其中对环丙基自由基及其正负离子的热开环反应作出以下三方面的预言：是否存在过渡态;产物的立体选择;反应的相对难易程度．并分别使用UHF方法和CASSCF方法做势能面计算,结果和理论预言相符．