Aryl Anions Research Articles

Organolithium Displacement of Aryl Anions from Tertiary Phosphine Derivatives of Diphenyl Ether

Organolithium Displacement of Aryl Anions from Tertiary Phosphine Derivatives of Diphenyl Ether

An approach to pancratistatin from myo-inositol

A highly advanced intermediate ( 15) for the synthesis of 7-deoxypancratistatin was prepared in 11 steps from myo-inositol. Introduction of the C 10bAr bond through an intramolecular epoxide opening with an aryl anion is the key step in this approach.

Organolithium Displacement of Aryl Anions from Tertiary Phosphine Derivatives of Diphenyl Ether

Abstract Methyllithium displaces a phenyl anion from 10-phenyl-10H-phenoxaphosphine to produce a 70:30 mixture of 10-methyl-10H-phenoxaphosphine and starting phosphine. Butyllithium gives 50% conversion to 10-butyl-10H-phenoxaphosphine. These reactions could take place either by a one-step nucleophilic displacement or by ring cleavage followed by recyclization. To show the feasibility of the two-step process, non-heterocyclic lithiated tertiary phosphines were generated and shown to cyclize to phenoxaphosphines. For example, reaction of 2-phenoxyphenyldiphenylphosphine with phenyllithium produced 10-phenyl-10H-phenoxaphosphine (by lithiation ortho to oxygen followed by cyclization) along with triphenylphosphine (by direct displacement of 2-lithiodiphenyl ether). Other compounds prepared in this work: 2,2′-bis(diphenylphosphino)-diphenyl ether, bis(2-phenoxyphenyl)phenylphosphine, tris(2-phenoxyphenyl)phosphine, 4-carboxy-10-phenyl-10H-phenoxaphosphine, and the oxides and sulfides of the phosphines.

Conversions of 2-aminopyridines into 5-substituted derivatives mediated by 1-hydroxymethylbenzotriazole

2-Aminopyridines are benzotriazolylmethylated at the 5-position by 1-hydroxymethylbenzotriazole. The methylene group of 2-amino-5-(benzotriazolylmethyl)pyridines 6 can be mono- or di-lithiated and subsequently substituted by various electrophiles. The benzotriazole moiety in both the primary products 6, and in their methylene-substituted derivatives 8 and 9, is displaced by alkyl and aryl anions derived from Grignard reagents, or by alkoxide and thioalkoxide anions. Moreover, the derivative 8a undergoes smooth elimination of benzotriazole under basic conditions to generate the 5-vinyl-substituted 2-aminopyridine 12. These approaches allow the synthesis of many new types of 5-substituted 2-aminopyridines.

Utilization of Me 3SiSnBu 3 in organic synthesis : I. Generation of a stannyl anion from Me 3SiSnBu 3 and R 4NX

A metal free stannyl anion generated from Me 3SiSnBu 3 and R 4NX in DMF reacted with an aryl halide bearing carbonyl group to produce an aryl anion via the so-called halogen-metal exchange process, which reacted with a carbonyl group to afford a cyclized product in good yield.

Novel cyclization by stannyl anion generated from (trimethylsilyl)tributylstannane (Me3SiSnBu3) and fluoride ion. Application to natural product synthesis

Stannyl anion, generated from Me 3 SiSnBu 3 and (Et 2 N) 3 S + TMSF 2 - (TASF) or CaF in DMF, was quite effective for generation of an aryl or vinyl anion, which reacted with a carbonyl group intramolecularly to provide the useful cyclized product in good yield

Reaction of metal free Bu 3Sn − generated from Bu 3SnSiMe 3-R 4NX with an aryl or vinyl halide

Metal free stannyl anion generated from Bu 3SnSiMe 3 and R 4NX in DMF reacted with an aryl or vinyl halide to produce the aryl or vinyl anion via so-called halogen-metal exchange process, which reacted with internal carbonyl group to afford cyclized product in good yield.

Stable fluorinated aryl- and cyclopentadienyl-anions

Aryl anions of type (1) are potentially useful probes to study the effect of fluorine substituents on charge distributed in an aromatic ring (1a), which is of obvious interest in relation to nucleophilic aromatic substitution. ▪Consequently, we have synthesised a series of stable aryl anions of type ArF-CX̄Y and the spectra of these systems will be discussed.We will also describe a rational synthesis to a series of novel stable fluorinated cyclopentadienyl anions of general structure (3), via the dienes (2). ▪

Reactions of Trialkylstannane Anions R3Sn− with Arylstannanes ArSnR3′

Abstract The reactions of trialkylstannane anions R3Sn− with arylstannanes ArSnR3′ have been investigated; trialkylstannane anions with arylstannanes at 50 °C gave substitution products ArSnR3 in good yields. Most of these substitution products are diverted to reduction products ArH when t-butylamine for trapping free anionoids is present in the reaction mixture. These results are consistent with an initial tin–alkali metal exchange or an electron-transfer forming aryl anions and distannanes which subsequently react to the substitution products. Aryl radical intermediates by an electron-transfer process are also important in the reactions of trialkylstannane anions with electron-withdrawing groups-substituted arylstannanes, 1-naphthylstannanes, diphenylstannanes, and triphenylmethylstannane as good electron acceptor substrates.

ChemInform Abstract: Electron Transfer Catalyzed Reactions. Electrochemical Induction of the Hydrogen Atom Transfer Oxidation of Alcohols and Other Substrates by Aromatic Halides.

AbstractThe title reaction in the presence of H‐atom donors such as (II) or urea, DMF, or N,N‐diethylformamide proceeds via reductive cleavage of (I), H abstraction from (II), and deprotonation to give the intermediate aryl anion radical, hydroxyalkyl radical and ketyl anion radical, respectively.

Simultaneous use of empirical and semiempirical substituent parameters as a new method of analysis of the ortho effect. Application in reactions via aryl anion intermediates

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSimultaneous use of empirical and semiempirical substituent parameters as a new method of analysis of the ortho effect. Application in reactions via aryl anion intermediatesPascual SeguraCite this: J. Org. Chem. 1985, 50, 7, 1045–1053Publication Date (Print):April 1, 1985Publication History Published online1 May 2002Published inissue 1 April 1985https://doi.org/10.1021/jo00207a028RIGHTS & PERMISSIONSArticle Views95Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Evidence in favour of Exner isokinetic method to determine activation parameters

Exner method to ascertain the isokinetic relationship (IKR) and obtain isokinetic activation parameters in a reaction series, although well known, is relatively little applied; A great many chemists do not appear to be convinced of the superiority of isokinetic activation parameters over conventional ones, and the IKR itself is still a controversial matter. From our kinetic results on the decarboxylation of a series of 4-substituted-2,6-dinitrobenzoate ions in aqueous solution, activation parameters were calculated, both by Exner method and by a conventional one. The obtained isokinetic activation enthalpies correlate much better (r = 0.998, 5 points) than the conventional ones (r = 0.97, 5 points), with the energies (calculated at the STO-3G ab initio level) for the formation of substituted aryl anions, the latter being a process expected to be energetically related to the decarboxylation reaction. This is the first example of non-statistical evidence in favour of Exner method to determine activation parameters, a method that we strongly advocate.

FLUORIDE-INDUCED 1,2-ELIMINATION OF O-TRIMETHYLSILYLPHENYL TRIFLATE TO BENZYNE UNDER MILD CONDITIONS

Abstract Fluoride-induced 1,2-elimination of o-trimethylsilylphenyl triflate provided a convenient route to benzyne under mild conditions where detriflation from an intermediary aryl anion appeared to occur in preference to protonation even in the presence of alcohols.

ChemInform Abstract: AZOSULFONES: VERSATILE PRECURSORS FOR ARYL RADICALS, ARYL CATIONS, ARYL ANIONS, CARBENES, AND BENZYNES

Chemischer InformationsdienstVolume 14, Issue 8 Reviews ChemInform Abstract: AZOSULFONES: VERSATILE PRECURSORS FOR ARYL RADICALS, ARYL CATIONS, ARYL ANIONS, CARBENES, AND BENZYNES N. KAMIGATA, N. KAMIGATASearch for more papers by this authorM. KOBAYASHI, M. KOBAYASHISearch for more papers by this author N. KAMIGATA, N. KAMIGATASearch for more papers by this authorM. KOBAYASHI, M. KOBAYASHISearch for more papers by this author First published: February 22, 1983 https://doi.org/10.1002/chin.198308347AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume14, Issue8February 22, 1983 RelatedInformation

Cathodic reduction of aromatic halides. an evidence for an ionic mechanism

A study on the cathodic reduction of the C-X bond in aryl vicinal dihalides and monohalides is made, demostrating in an unequivocal way the presence in all the cases of aryl anion intermediates.

Azosulfones: Versatile Precursors for Aryl Radicals, Aryl Cations, Aryl Anions, Carbenes, and Benzynes

Abstract The preparation, physical properties, and reactions of arylazo aryl sulfones are described. The mechanism of the decomposition of arylazo aryl sulfones is discussed. Arylazo aryl sulfones afford aryl cations, aryl radicals, and aryl anions under strongly acidic, weakly basic, and strongly basic conditions, respectively. Carbenes are formed from alkenylazo sulfones while cyclic azosulfones such as 1,2,3-benzothiazole 1,1-dioxides, afford benzynes. Tosylazocyclohexene reacts with enamines to give [2 + 3] cycloadducts.

The rates of base cleavage of substituted 2-thienyltrimethylsilanes. AB initio calculations of the acidities of monosubstituted thiophens

Rates of cleavage in NaOMe-MeOH at 50°C have been determined for the mono-substituted 2-trimethylsilylthiophens X·C 4H 2S·SiMe 3-2 with X = H, 3-NO 2, 3-Br, 4-Br-, and 5-NO 2, -CN, -COPh, -Me, -OMe and -NMe 2, and for one disubstituted compound, 4,5-Br 2-C 4HS-SiMe 3-2. For several compounds the rate and product isotope effects have also been determined. The energies involved in the process X·C 4H 3S → X·C 4H 2S − for deprotonation at the 2-position have been calculated by an ab initio method (STO-3G), and the results used in analysis of the substituent effects in the cleavage of the XC 4H 2S· SiMe 3-2 compounds. The results are consistent with the view the aryl anions separate in the rate determining step of the cleavage. The isotope effects are all close to unity, whereas by comparison with results for XC 6H 4CH 2SiMe 3 and related species of similar reactivity, values in the region of 10 would be expected for the 3- and 5-NO 2 compounds if the product isotope effect for a carbanion R depended only in the p K a of RH. The difference between the thienyl- and benzyl-type anions is attributed to the absence of conjugative delocalization of the charge in the former. Approximate p K a values are derived for the 2-positions of the X-C 4H 3S compounds.

Reaction of 1,3-dioxolans with iodine monochloride: the scope and mechanism of formation of 1,3-dioxolan-2-ylium dichloroiodates(I)

Treatment of a series of 2-substituted-4,4,5,5-tetramethyl-1,3-dioxolans with iodine monochloride afforded the appropriate 2-substituted-4,4,5,5-tetramethyl-1,3-dioxolan-2-ylium dichloroiodate(I) salts in excellent yields. In contrast to the stable 2-aryl-substituted salts, the 2-alkyl and unsubtituted derivatives were relatively labile. While 2-phenyl-1,3-dioxolan and 2-phenyl-1,3-dioxan afforded low yields of unstable salts, crystalline products could not be isolated from 4,5-disubstituted dioxolans. The reaction was inhibited by electron-withdrawing 4- and 5-substituents. From a study of the effects of photolysis and added iodine, the mechanism is proposed to involve a hydride ion transfer. Possible reasons for the formation of dichloroiodate(I) rather than monohalide salts, are outlined. The stability of the 2-aryl-substituted salts is discussed in terms of charge distribution in the cation and possible aryl–anion interactions.

The Reactivity of t-Butyldimethylsilyl Ethers Towards Some Stabilised Carbanions

Abstract The t-butyldimethylsilyl (TBDMS) protection1–3 of alcoholic and phenolic hydroxy groups has attained much importance of late. Certain shortcomings, however, of this protective method have recently come to light. These include acyl migration4 during the fluoride anion mediated desilylation of acylated/silylated glycerols, and cleavage of TBDMS groups under catalytic hydrogenation conditions intended for benzyl ether cleavage4. Further, aryl anions of trimethylsilyl protected phenols have been shown5 to rearrange into o-trimethylsilyl-phenolates; similar reaction of a TBDMS protected phenol has been observed6 in this laboratory. The more labile trimethylsilyloxy group has also been reported7 to act as a leaving group, if present at an allylic or benzylic site, towards a variety of nucleophiles (H−, alkyl Grignards, malonate anion). However, benzyl TBDMS ether is stable towards ethylmagnesiumbromide under reflux6.

Are arylcopper compounds intermediates in the exchange reaction between aryl halides and copper(I) salts?

exchange between aryl halides and anions of copper salts haL; generally been rationalized in terms of a copper-assisted nucleophilic displacement reaction involving a four-center transition state or intermediate 1,2 , eq. 1. At-Hal + XCuL, Z [Ar:$:C”L,] ; ArX + HalCuL3