The use of aminoiminomethanesulfinic acid (thiourea dioxide) under phase transfer conditions for generating organochalcogenate anions. Synthesis of sulfides,selenides and tellurides

A procedure is described which allows for the in situ synthesis of arylalkyl, diaryl and dialkylchalcogenides under phase transfer conditions starting from the corresponding diorganodichalcognides. The dichalcogenides are reduced by aminoiminomethanesulfinic acid (thiourea dioxide) in alkaline medium and catalyzed by a quaternary ammonium salt. The reduction proceeds easily for diaryl disulfides and diaryl diselenides at a sodium hydroxide concentration of 13%; diaryl ditellurides require a 50% sodium hydroxide solution to give the aryl tellurolate anion. The dialkyl diselenides and dialkyl ditellurides are more difficult to reduce. The intermediate arylthiolates and arylselenolates are quenched by alkyl and activated aryl halides to give the corresponding sulfides and selenides in high yield (77–97%). The aryltellurolates react with alkyl halides giving the aryl alkyl tellurides in 81–96% yield. The procedure could not be successfully used for the synthesis of dialkylselenides and dialkyl tellurides; low yields and mixture of products were formed.     

Reinvestigation of the grignard reactions with formic acid. A convenient method for preparation of aldehydes

Grignard reagents react with formic acid in tetrahydrofuran to produce aldehydes in relatively good yields Various aldehydes such as alkyl, aryl, allyl, benzyl and vinyl aldehydes were prepared from the corresponding Grignard reagents. The reaction with vinyl Grignard reagents proceeded with retention of configuration.     

New synthesis of vinyl selenides nucleophilic substitutions of unactivated vinyl halides by selenide anions

Alkyl and aryl selenide anions react with unactivated vinyl halides, in dipolar aprotic solvents, to give alkyl or aryl vinyl selenides in good yields. These reactions are stereospecific and occur with retention of configuration.     

Samarium diiodide induced reductive cleavage of the Te–Si bond in phenyltellurotrimethylsilane: A novel method for the synthesis of alkylphenyl tellurides,telluroesters, and β‐phenyltelluro esters (nitriles)

Phentyltellurotrimethylsilane (1) was reduced by samarium diiodide in tetrahydrofuran (THF) to produce samarium phenyltellurolate. This new tellurolate anion reacted smoothly with alkyl and benzyl halides to give alkyl and benzyl‐phenyl tellurides in good yields under mild and neutral conditions. The samarium tellurolate also reacted with acyl halides or anhydrides to give telluroesters, and the 1,4‐addition of samarium tellurolate to α, β‐unsaturated esters (nitriles) gave β‐phenyltelluro esters (nitriles). © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 471–474, 1999     

某些含芳碲基或烷碲基的1, 4-苯醌和1, 4-萘醌衍生物

四氯-1,4-苯醌(1)和2,3-二氯-1,4-萘醌(2)中的氯相当活泼,能和许多亲核试剂反应,如醇和酚;硫醇和硫酚;胺及许多含NH的杂环化合物。1和2与磷亲核试剂的反应也是已知的,本文报道1及2和芳碲基或烷碲基亲试剂的反应。     

Diphenylprolinol Silyl Ether Catalyzed Asymmetric Michael Reaction of Nitroalkanes and β,β‐Disubstituted α,β‐Unsaturated Aldehydes for the Construction of All‐Carbon Quaternary Stereogenic Centers

The asymmetric Michael reaction of nitroalkanes and β,β‐disubstituted α,β‐unsaturated aldehydes was catalyzed by diphenylprolinol silyl ether to afford 1,4‐addition products with an all‐carbon quaternary stereogenic center with excellent enantioselectivity. The reaction is general for β‐substituents such as β‐aryl and β‐alkyl groups, and both nitromethane and nitroethane can be employed. The addition of nitroethane is considered a synthetic equivalent of the asymmetric Michael reaction of ethyl and acetyl substituents by means of radical denitration and Nef reaction, respectively. The short asymmetric synthesis of (S)‐ethosuximide with a quaternary carbon center was accomplished by using the present asymmetric Michael reaction as the key step. The reaction mechanism that involves the E/Z isomerization of α,β‐unsaturated aldehydes, the retro‐Michael reaction, and the different reactivity between nitromethane and nitroethane is discussed.     

Iron powder and tin/tin chloride as new reducing agents of Meerwein arylation reaction with unexpected recycling to anilines

Abstract

Simple and rapid route for Meerwein arylation reaction using iron powder or a mixture of tin/tin chloride has been developed. In the presence of iron powder, different aryl diazonium salts reacted with methyl vinyl ketone, acrylates, and isopropenyl acetate. Production of oximes was detected as the main product with acrylates or in a mixture with β-aryl methyl ketones in the case of methyl vinyl ketone. The in situ produced HNO₂ from an excess of NaNO₂/HCl was trapped by alkyl aryl radical to form oximes in the E configuration form. The presence of tin/tin chloride mixture in the reaction of the aryl diazonium salts with methyl vinyl ketone produced Michael products along with β-aryl methyl ketones. The predicted α-aryl methyl ketones from the reaction of isopropenyl acetate with the diazotized anilines were obtained using iron or tin/tin chloride mixture.     

Nickel-catalyzed enantioselective vinylation of aryl 2-azaallyl anions

A unique enantioselective nickel-catalyzed vinylation of 2-azaallyl anions is advanced for the first time. This method affords diverse vinyl aryl methyl amines with high enantioselectivities, which are frequently occurring scaffolds in natural products and medications. This C–H functionalization method can also be extended to the synthesis of enantioenriched 1,3-diamine derivatives by employing suitably elaborated vinyl bromides. Key to the success of this process is the identification of a Ni/chiraphos catalyst system and a less reducing 2-azaallyl anion, all of which favor an anionic vinylation route over a background radical reaction. A telescoped gram scale synthesis and a product derivatization study confirmed the scalability and synthetic potential of this method.

A unique enantioselective Ni-catalyzed vinylation of 2-azaallyl anions is advanced. This method affords vinyl aryl methyl amine or 1,3-diamine derivatives with high enantioselectivities, which are frequently occurring scaffolds in medications.     

Organocatalytic Michael addition of aldehydes to vinyl sulfones: enantioselective alpha-alkylations of aldehydes and their derivatives

Organocatalytic asymmetric Michael reaction of unmodified aldehydes to vinyl sulfones catalyzed by silylated biarylprolinol afforded the desired Michael products with exceptional enantioselectivity. The described enantioselective addition to vinyl sulfones, in combination with desulfonation, offers a unique, asymmetric entry to alpha-alkylated aldehydes and their derivatives.     

The unprecedented reaction of dimethylsulfonium methylide with Michael acceptors: synthesis of 1-substituted vinyl silanes and styrenes

Rather than the usual cyclopropanation, conditions for an unprecedented elimination reaction from the adduct of dimethylsulfonium methylide and various Michael acceptors have been established leading to functionalized 1-substituted alkenes. In silyl substituted substrates (2a and 2h), where a facile Peterson-type olefination is possible from the adduct; elimination took place instead to give functionalized 1-substituted vinyl silanes. Aryl substituted Michael acceptors (2b-e, 2g and 2i-k) also underwent a similar kind of olefination to give 1-substituted styrene derivatives with moderate yields along with a side product, which arose by nucleophilic demethylation from the adduct of dimethylsulfonium methylide and arylidene malonates. Hammett studies revealed that selectivity for olefination vs. demethylation increases as the aryl substituent becomes more electron deficient. Alkylidene malonates (2f and 2l) with a beta-alkyl substituent did not favour the olefination process. Sequential addition of Michael acceptors and alkyl halides to a mixture of dimethylsulfonium methylide and sodium dimsylate provided olefination followed by alkylation on the active methine group. A mechanistic pathway has been formulated from the studies of a few sulfonium methylides.     

Tailored Palladate Tunable Aryl Alkyl Ionic Liquids (TAAILs)

We present a new class of tunable aryl alkyl ionic liquids (TAAILs) containing different palladate counter ions. Solid-state structures for representative compounds have been obtained. Their properties are presented in comparison to those of newly synthesized and reported palladate ionic liquids with conventional counter ions. It was found that the aryl substitution pattern and the type of anion have a profound influence on the melting point. The speciation of the different anions in solution has been rationalized by DFT calculations.     

Phosphinamide-directed benzylic lithiation. Application to the synthesis of peptide building blocks

N-benzyldiphenylphosphinamides are deprotonated at the NCalpha position diastereospecifically upon treatment with t-BuLi in diethyl ether at low temperature. The reaction of the anions with alkyl, acyl, and tin halides, aliphatic and aromatic aldehydes, and Michael acceptors allowed installation of a variety of functional groups into the benzylic arm in excellent yields. Cleavage of the P-N linkage affords 1,2-amino alcohols and alpha-, beta-, and gamma-amino acids.     

Cocatalysis in phase-transfer catalyzed fluorination of alkyl halides and sulfonates

Phase-transfer catalyzed (PTC) fluorination of alkyl halides and sulfonates with solid KF proceeds efficiently when cocatalyst triphenyltin fluoride is used. The cocatalytic action of the tin compound consists in continuous formation of difluorotriphenylstannate anion that as the tetraalkyloammonium salt enter the solution where it reacts with alkyl halides to produce alkyl fluorides. The cocatalytic system was used to synthesis of 1,1-difluoroalkanes in two steps from aldehydes. A new kind of PTC was elaborated in which Ph₃SnF acts as phase transfer catalyst via continuous formation of potassium salts of diflurotriphenylstannate anions soluble in dipolar aprotic solvents. A new, simple and general method of synthesis of tetraalkylammonium and potassium salts of difluorotriorgano-tin, silicon and germanium anions is reported.     

Expanding the Electrochemical Window: New Tunable Aryl Alkyl Ionic Liquids (TAAILs) with Dicyanamide Anions

A set of new tunable aryl alkyl ionic liquids (TAAILs) based on the 1-aryl-3-alkyl imidazolium motif has been synthesized, in which the following variables were systematically changed: alkyl chain length, aryl substitution (group and position), and counter ion. TAAILs with dicyanamide (DCA) and bis(trifluoromethylsulfonyl)imide (N(SO₂CF₃)₂, NTf₂) anions showed remarkable differences of their physical properties: NTf₂ ionic liquids were found to have high decomposition temperatures and viscosities well below those of the DCA TAAILs. In contrast, the dicyanamide anion increased the electrochemical stability leading to TAAILs with an extremely wide electrochemical window of up to 7.17 V. Additionally, both classes of TAAILs extract transition metals from aqueous solutions: TAAILs with the DCA anion extract both platinum and copper while TAAILs with the NTf₂ anion are selective towards platinum. This demonstrates that minor changes of the molecular structure lead to TAAILs with drastically changed physicochemical properties.     

The use of sulfines in nucleophilic acylation reactions

The thiophilic addition of MeLi and BuLi to aromatic alkylthio- and arylthio sulfines has been studied. The resulting dithioacetal monoxides are isolated in high yields. Reactions of MeLi with aromatic arylsulphinyland arylsulfonyl sulfines give the corresponding dithioacetal di- and trioxidcs. Acid treatment of dithioacetal monoxides results in aromatic aldehydes. The nucleophilic acylation of the acylanion equivalents obtained from sulfines is investigated. Alkylation of the dithioacetal monoxide anions, prepared in situ from MeLi and sulflnes of the type Ar(RS)CSO. with primary alkyl halides leads to dithioketal monoxide which upon acidolysis under anhydrous conditions are converted into vinylsulfides. The mechanism of the formation of the vinyl sulfides is discussed. The acylanion equivalents are acylated with benzoylchloride, CO₂ and benzaldehyde. The use of Cu¹ and 18-crown-6 as a catalyst appears to be crucial in some reactions. Michael additions of the dithioacetal monoxides to acrylonitrile are described.     

Nickel-catalyzed Kumada cross-coupling reactions of tertiary alkylmagnesium halides and aryl bromides/triflates

We report a Ni-catalyzed process for the cross-coupling of tertiary alkyl nucleophiles and aryl bromides. This process is extremely general for a wide range of electrophiles and generally occurs with a ratio of retention to isomerization >30:1. The same procedure also accommodates the use of aryl triflates, vinyl chlorides, and vinyl bromides as the electrophilic component.     

Visible‐Light‐Promoted Nickel‐ and Organic‐Dye‐Cocatalyzed Formylation Reaction of Aryl Halides and Triflates and Vinyl Bromides with Diethoxyacetic Acid as a Formyl Equivalent

A simple formylation reaction of aryl halides, aryl triflates, and vinyl bromides under synergistic nickel‐ and organic‐dye‐mediated photoredox catalysis is reported. Distinct from widely used palladium‐catalyzed formylation processes, this reaction proceeds by a two‐step mechanistic sequence involving initial in situ generation of the diethoxymethyl radical from diethoxyacetic acid by a 4CzIPN‐mediated photoredox reaction. The formyl‐radical equivalent then undergoes nickel‐catalyzed substitution reactions with aryl halides and triflates and vinyl bromides to form the corresponding aldehyde products. Significantly, besides aryl bromides, less reactive aryl chlorides and triflates and vinyl halides serve as effective substrates for this process. Since the mild conditions involved in this reaction tolerate a plethora of functional groups, the process can be applied to the efficient preparation of diverse aromatic aldehydes.     

Stereospecific synthesis of divinyl selenides nucleophilic substitutions of unactivated vinyl halides by vinyl selenide anions

Vinyl alkyl selenides can be dealkylated by nucleophilic substitution or by electron transfer to give vinyl selenide anions which retain the configuration of the starting products. The same anions are also produced by electron transfer from vinyl acetyl selenides. The vinyl selenide anions react with vinyl halides, in DMF or DMA, to give divinyl selenides. These reactions occur with retention of configuration and represent a new example of nucleophilic substitutions of unactivated vinyl halides.     

β-氟烷基烯基碘与硫酚负离子的反应

在CH~3CN中,β-氟烷基烯基碘与硫酚负离子能发生消除-加成反应生成碘被取代的产物;硫醇负离子及氧负离子对β-氟烷基烯基碘进攻则生成消除产物氟烷基炔烃。     

Increased Halide Recognition Strength by Enhanced Intercomponent Preorganisation in Triazolium Containing [2]Rotaxanes

Three triazolium‐based [2]rotaxanes containing different sized axle and macrocycle components were synthesised in good yields (40–57 %) through chloride anion templation. The anion recognition properties of the interlocked receptor systems were investigated using ¹H NMR titration experiments: all three rotaxanes display impressive selectivities for halide anions over the more basic oxoanion acetate. The rotaxanes incorporating shorter, more rigid axle components with aryl‐substituted triazolium groups display substantially higher anion binding affinities than those with longer, bis‐alkyl‐substituted heterocycles, which is attributed to the increased intercomponent preorganisation afforded by the smaller axle component. Computational DFT and molecular dynamics simulations composed of unconstrained and umbrella sampling simulations corroborate the experimental observations.