Thallium Triacetate Research Articles

ChemInform Abstract: Intramolecular Cyclization of Some Unsaturated Alcohols by Means of Thallium Triacetate.

ChemInform Abstract: Intramolecular Cyclization of Some Unsaturated Alcohols by Means of Thallium Triacetate.

ChemInform Abstract: Oxidative Activation in Aromatic Substitutions. Reactions of N,N-Dimethylanilines with Secondary Anilines Promoted by Thallium Triacetate.

The reactions of N,N-dimethyl-p-anisidine (1a), N,N-dimethylaniline (1b), and N,N-dimethyl-p-fluoroaniline (1c) toward secondary anilines 2(a−d)-H in the presence of thallium triacetate sesquihydrate have been studied as representative of a novel oxidatively activated aromatic substitution affording 1,4-benzenediamine derivatives 3a−d. All of the substrates considered gave substitution with diphenylamine (2d-H). However, with anilines 2b,c-H, only 1a underwent substitution, and substrates 1b,c were practically unreactive. The observed differences in reactivity are well accounted for within a mechanistic framework wherein oxidative activation of both the substrate and the secondary aniline is regarded as alternatively (or simultaneously) possible, depending on the redox characteristics of the reactants. For instance, it can be stated, beyond any reasonable doubt, that reactions of 1a with 2b,c-H proceed via nucleophilic attack of the latter on 1a+•, and that the reaction of 1a−c with 2d-H must involve the ...

Ciclização do lapachol induzida por sais de tálio III

This work describes the cyclization of lapachol (1) induced by thallium triacetate (TTA) and thallium trinitrate (TTN) in several solvents using magnetic stirring and under microwave irradiation. a-Xyloidone (2) - dehydro-a-lapachone - was obtained as the main product in these reactions in 20 75% yield. However, rhinacanthin-A (4) was isolated as main product in a 40% yield, using TTA and acetic anhydride:water (1:1) as solvent, and dehydro-iso-a-lapachone (3) in 21% yield, using TTA and dichloromethane as solvent. The reaction time decreased drastically under microwave conditions, but the yields of these reactions were not the expected.

Tl(III) initiated polymerization of methyl methacrylate in micellar phase

AbstractThe polymerization kinetics of methyl methacrylate (MMA) was studied, using Tl(III)‐cyclohexanone (CH) redox system as initiator, in the presence of emulsifier [i.e., sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and thallium triacetate (TX‐100)] over a temperature range of 25–45°C. The effect of various concentrations of MMA, Tl(III), cyclohexanone, H+, and varying ionic strengths on the rate of polymerization, rate of Tl(III) consumption (−RTl), and the percentage of monomer conversion were examined in the presence of 0.015M SDS. The kinetic results of polymerization in the absence and presence of 0.015M SDS were compared in terms of overall activation energy (Ea) for the process. The viscosity‐average molecular weight (MV) of the polymers, obtained in the presence of varying concentrations of anionic surfactant (SDS), was also determined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2480–2485, 2004

OXIDATION OF HANTZSCH 1,4- DIHYDROPYRIDINES TO PYRIDINES WITH THALLIUM TRIACETATE

Hantzsch 1, 4-dihydropyridines (1,4-DHPs) can be oxidized to the corresponding pyridine derivatives by thallium triacetate in high yields.

Oxidative activation in aromatic substitutions. Reactions Of N, N-dimethylanilines with secondary anilines promoted by thallium triacetate

The reactions of N,N-dimethyl-p-anisidine (1a), N,N-dimethylaniline (1b), and N,N-dimethyl-p-fluoroaniline (1c) toward secondary anilines 2(a−d)-H in the presence of thallium triacetate sesquihydrate have been studied as representative of a novel oxidatively activated aromatic substitution affording 1,4-benzenediamine derivatives 3a−d. All of the substrates considered gave substitution with diphenylamine (2d-H). However, with anilines 2b,c-H, only 1a underwent substitution, and substrates 1b,c were practically unreactive. The observed differences in reactivity are well accounted for within a mechanistic framework wherein oxidative activation of both the substrate and the secondary aniline is regarded as alternatively (or simultaneously) possible, depending on the redox characteristics of the reactants. For instance, it can be stated, beyond any reasonable doubt, that reactions of 1a with 2b,c-H proceed via nucleophilic attack of the latter on 1a+•, and that the reaction of 1a−c with 2d-H must involve the ...

ChemInform Abstract: Reaction of β,γ‐Unsaturated Carboxylic Acids with Thallium Triacetate (TTA): Lactonization vs Oxidative Decarboxylation.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Reaction Of β,γ-Unsaturated Carboxylic Acids With Thallium Triacetate (Tta): Lactonization VS Oxidative Decarboxylation

The reaction of six β,γ-unsaturated carboxylic acids with thallium triacetate (TTA) was studied. The nature of the products is highly sensitive to the substitution pattern of the substrates. Aliphatic acids gave mainly lactones, while those bearing an aromatic ring furnished only decarboxylation products.

Oxidative Activation in Aromatic Substitutions. Reactions of N,N-Dimethylanilines with Secondary Anilines Promoted by Thallium Triacetate

Oxidative Activation in Aromatic Substitutions. Reactions of <i>N</i>,<i>N</i>-Dimethylanilines with Secondary Anilines Promoted by Thallium Triacetate

Cyclization of unsaturated monoterpenic alcohols mediated by thallium (III) salts

The reaction of thallium triacetate and thallium trinitrate with four monoterpenic unsaturated alcohols (isopulegol, neo-isopulegol, cis-carveol and α-terpineol), in AcOH:H 2O (1:1, vol/vol) as solvent, led to the corresponding β-hydroxy-cyclic ethers with high regio- and stereoselectivity, in moderate to good yields. A mechanism of ring-contraction or ring-expansion of the oxythallated adduct is proposed, based on the substitution patterns of each double bond.

Intramolecular Cyclization of Some Unsaturated Alcohols by Means of Thallium Triacetate

AbstractReactions of some primary and secondary Δ4‐, Δ5‐ and Δ6‐alkenols with thallium triacetate (TTA) in benzene, acetic acid and chloroform as solvent have been investigated. When terminally unsubstituted Δ4‐alkenols, such as 4‐penten‐1‐ol (5a) and 5‐hexen‐2‐ol (5b), are treated with TTA in benzene, β‐acetoxylated tetrahydrofurans 8a and 8b are obtained. However, when the reaction is carried in acetic acid the products are both regioisomers, i.e. five‐ and six‐membered cyclic ethers (8a, 8b, 7a and 7b). 4‐Methyl‐4‐penten‐1‐ol (5c) is converted in benzene into a mixture of products (8c and 7c) in which the tetrahydropyran derivative 7c is predominant, and in acetic acid it is the sole cyclization product. Terminally dialkylated alkenols, such as 5‐methyl‐4‐hexen‐1‐ol (1b) and 6‐methyl‐5‐hepten‐2‐ol (1c), are converted into β‐acetoxylated (4b and 4c) and unsaturated cyclic ethers (9a and 9b), in both cases of the tetrahydrofuran type. 5‐Hexen‐1‐ol (10) and 6‐hepten‐1‐ol (11) cyclize to the corresponding six‐ (13) and seven‐membered cyclic ether (14), respectively. Organothallium intermediates have been isolated and identified in the cases of alcohols 5a, 5c and 10, proving that the TTA addition to the double bond has originally obeyed the Markovnikov rule.

Thallium (III) Salts-Induced Lactonizations of Unsaturated Carboxylic Acids

Abstract The reaction of four γ,δ-unsaturated carboxylic acids with thallium triacetate and thallium trinitrate, leading regioselectively to the corresponding γ-lactones, is described.

Pheromone Synthesis, XCVIII. Conversion of the Enantiomers of Sulcatol (6‐Methyl‐5‐hepten‐2‐ol) to the Enantiomers of Pityol [trans‐2‐(1‐Hydroxy‐1‐methylethyl)‐5‐methyltetrahydrofuran], a Male‐Specific Attractant of the Bark Beetle Pityophthorus pityographus

AbstractEnantiomerically pure (R)‐sulcatol (2a) was synthesized from ethyl (R)‐3‐hydroxybutanoate (3). Cyclization of (R)‐2a with thallium(III) triacetate yielded (2S,5R)‐pityol (1). In the same manner, (S)‐2a and (2R,5S)‐1 were synthesized from (S)‐3.

The stereoselective synthesis of terpene tetrahydrofurans using thallium triacetate

The reaction of diterpenes 1–3 and monoterpenes 9 , 10 with thallium triacetate leads stereoselectively to the tetrahydrofuran products 5–7 and 11 , 12 respectively, by 5-Endo-Trig cyclisation of the 3-alkenol system.

Kinetics of the oxidation of cyclohexene by thallium(III) acetate

AbstractThe kinetics of the reaction by which thallium(III) acetate oxidizes cyclohexene in glacial acetic acid medium, has been studied by UV spectrophotometric observation at 30°C. The consumption of thallium(III) acetate follows a second‐order rate law exhibiting first‐order dependence on each of thallium(III) acetate and cyclohexene; however, the first‐order dependence on cyclohexene disappears at high cyclohexene concentrations as pseudo‐first‐order conditions prevail above 0.2 M cyclohexene. A steady‐state model of the following form is proposed: equation image where Tl, Cy, and Com are units of Thallium(III) acetate, cyclohexene, and a reaction complex. The value of k2 has been evaluated as 0.00027 and (k−1 + k2) as 0.0385k1. For low thallium(III) acetate concentrations the reaction kinetics follow the rate law: where α = the excess concentration of cyclohexene over thallium(III) triacetate. For thallium(III) acetate concentrations above 0.02 M, double salt formation of thallium(III) acetate with product thallium(I) acetate removes thallium(III) acetate from the reaction and a modified rate law is observed. Runge–Kutta numerical solutions to the differential equations provide confirmation that the rate expressions are valid in predicting the observed concentrations of thallium(III) acetate.

Hydride shift in the solvolysis of 5-substituted PGi 1 derivatives

Silver ion mediated solvolysis of 5-iodo-PGI 1 derivatives as well as the reaction of PGF 2α methylester with thallium triacetate in acetic acid were studied with the aid of deuterium isotope labelling. In protic solvents (methanol, acetic acid) high retention (70–90%) of the deuterium label is compatible with a vicinal hydride shift whereas in non-protic solvents (e.g. pyridine) elimination occurs.

Kinetics and mechanism of thalliation of aromatic compounds in trifluoroacetic acid

A detailed kinetic study of aromatic thalliation in trifluoroacetic acid is reported. Owing to impurities present in the commonly used reagent, thallium(III) trifluoroacetate, which cause irreproducible reaction rates, thallium(III) triacetate sesquihydrate was used as the thalliating agent. The results obtained from u.v. data were analysed in terms of a rapidly formed π-complex followed by its rate-determining conversion into products. The overall secondorder rate constant showed a better Hammett correlation with σ+ than σ values yielding a ρ+ value of –8.3 which indicates greater charge development during the reaction than the corresponding mercuriation process. The stability of the intermediate π-complex however shows a greater sensitivity towards substituent effects than that of the mercury complexes. The overall free energies of activation of thalliation and mercuriation are very similar but significant variations occur in their component parameters, notably the entropy of formation of the π-complex is more negative for thallium than for mercury. The overall primary kinetic isotope effect of 4.3 is lower than that for mercuriation but the reverse is true for the conversion of the π-complex into products.

ChemInform Abstract: OXIDATION OF STEROID α‐DIKETONES BY THALLIUM(III) ACETATE. CRYSTAL AND MOLECULAR STRUCTURE OF A SPIROCYCLOPENTAN‐AS‐INDACENO DERIVATIVE OBTAINED FROM 3,4‐DIKETO STEROIDS

AbstractOxidation von 2,3‐Diketocholestan (I) mit Tl(O‐Ac)3 (II) in Essigsäure gibt das 3oz‐Carbomethoxy‐A‐nor‐Soz‐cholestanon (III).

Oxidation of steroid α-diketones by thallium (III) acetate : Crystal and molecular structure of a spiro-cyclopentan-a,s-indaceno derivative obtained from 3,4-diketo steroids

Treatment of 2,3-diketo-cholestane ( 1) with thallium triacetate in acetic acid afforded mainly 3α-carbomethoxy-A-nor-5α-cholestan-2-one ( 2). Under similar conditions, the 3,4-diketo steroids ( 3 and 4) underwent extensive rearrangement affording spiro-lactones ( 9 and 10), in low yields. The structural assignment of the spiro-cholestane derivative was supported by crystallographic X-ray analysis. This product was the result of A and B-ring contractions followed by acid-catalysed cyclization of an unsaturated carboxy intermediate.

Addition of thallium triacetate to PFG2αmethyl ester and related compounds in acetic acid. Nuclear magnetic resonance spectral study of novel dioxatricyclic and oxabicyclic products

Addition of Tl(OAc)3 in acetic acid to prostaglandin F2α methyl ester (1) and its congeners (4) and (5) gave, with participation of 9-OH, the bicyclic enol ethers (26) which reacted in situ with a further equivalent of Tl(OAc)3 to yield as the main products the dioxatricyclononane derivatives (2), (6), and (9) and (3), (7), and (10), respectively. Elucidation of the structure of the products by 1H and 13C n.m.r. is presented and a mechanism of the transformations based on model studies is proposed.