S-tosylsulfenamides,new electrophilic sulfosulfenylating agents

A method has been developed for the synthesis of thiosulfonates by the electrophilic addition of S-tosylsulfenamides to olefins or their electrophilic substitution in aromatic systems. SO₃, Py·SO₃, and BF₃·Et₂O were used as activators. The addition of S-tosylsulfenamides to olefins proceeds through electrophilic trans addition.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2623–2629, November, 1991.     

Réactivité des diénamines épiconjuguées des Δ3(9) hydrindénones—4V : Stéréochimie de la formation des δ-dicétones et de diverses attaques électrophiles

The cross-conjugated dienamines of Δ4 4-hydrindenones react with methylvinylketone (or other electrophilic reagents such as H⁺, I CH₃) at the face opposite to their angular substituent at R(8). The axial attack, in the case of methylvinylketone,. leads to the isomer of the δ-diketone in which the bulky oxo-3 butyl-1 group is in an axial position. The thermodynamic equilibrium shows that this isomer is the less stable one. Therefore, kinetic control of the reaction is a steric approach control. The high degree of stereoselectivity of the reaction depends both upon the nature of the substituent R(8) = H or CH₃ and the nature of the electrophilic reagent.     

Selective Synthesis of Cyclic Nitroene-Sulfonamides from Aliphatic Sulfamides and NOBF4

Described herein is the development of a desaturation and N-β-nitration reaction of cyclic amides, which is achieved by a selective hydrogen atom transfer (HAT)/oxidative desaturation/electrophilic nitration process. In this procedure, di-tert-butyl peroxide (DTBP) acted both as the oxidant and HAT reagent, and electrophilic NOBF₄ as nitration source. Notably, the application of produced cyclic nitroene-sulfonamides was showcased by their efficient transformations into 3-piperidones and poly-substituted piperidine derivatives.     

Monofluoromethyl‐Substituted Sulfonium Ylides: Electrophilic Monofluoromethylating Reagents with Broad Substrate Scopes

Two electrophilic monofluoromethylating reagents, monofluoromethyl(phenyl)sulfonium bis(carbomethoxy)methylide ( 3 a ) and monofluoromethyl(4‐nitrophenyl)sulfonium bis(carbomethoxy)methylide ( 3 b ), and their reactions under mild conditions with a variety of nucleophiles, such as alcohols and malonate derivatives, sulfonic and carboxylic acids, phenols, amides, and N heteroarenes, are described. Mechanistic studies with deuterated reagents [D₂] 3 a /[D₂] 3 b suggest that these monofluoromethylation reactions proceed through an electrophilic substitution pathway.     

Reactivity of hypervalent species of silicon: cleavage of the allyl-silicon bond

The reactivities of the silicon-allyl bonds in two kinds of pentacoordinated silicon species CH₂CHCH₂Si(o-O₂C₆H₄)₂ ⁻NMe₄⁺ (1) and CH₂CHCH₂- Si(OCH₂CH₂)₃N (2) has been compared. In the allyl transfer to carbonyl compounds under nucleophilic conditions (NaOMe, KF or Bu₄NF) and electrophilic conditions (TiCl₄, AlCl₃, BF₃) these two species show quite different behaviour. Complex 1 is activated by nucleophiles, while for 2 transfer occurs under electrophilic conditions. These results indicate that the reactivity of these species is a function of their overall charge and geometry.     

Generation of oxodiazonium ions 1. Synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides

Methods for the synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides, which include the reaction of 3-nitramino-4-(R-phenyl)furazans or their O-methyl derivatives with electrophilic agents, have been developed. Unsubstituted [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxide was synthesized from 3-nitramino-4-phenylfurazan upon the action of phosphorus anhydride or oleum, as well as from O-methyl derivative of 3-nitramino-4-phenylfurazan upon the action of H₂SO₄, MeSO₃H, CF₃CO₂H and BF₃·Et₂O, while 6-, 7-, 8-, and 9-nitro-substituted [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides — from the corresponding 3-nitramino-4-(nitrophenyl)furazans upon the action of the H₂SO₄-HNO₃ nitrating mixture. A suggestion has been made that an oxodiazonium ion is formed in these reactions from nitramines or their O-methyl derivatives upon the action of electrophilic agents, which is further involved into the intra-molecular reaction of electrophilic aromatic substitution (S _EAr) with the aryl group. The structure of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-N-oxides was confirmed by ¹H, ¹³C, and ¹⁴N NMR spectra. Theoretical studies by the B3LYP/6-311G(d,p) method of combined molecular system (O-methylated 3-nitramino-4-phenylfurazan + [H₃SO₄]⁺) resulted in calculation of thermodynamic parameters of the sequence of cascade elementary reactions leading to the formation of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxide.     

Synthesis of epoxy and aziridino malonyl peptidomimetics

Short malonyl dehydro peptides have been epoxidized using H₂O₂/Na₂WO₄ dihydrate. The obtained diastereomeric epoxides were separated by HPLC and successfully tested in the ring opening reaction with N-Boc l-cysteine methyl ester, to indicate their electrophilic behavior. Moreover, by a simple two-step reaction, the epoxy malonyl peptides can be converted into the corresponding aziridino malonyl peptides.     

Electrophile affinity and positional selectivity in electrophilic substitution reactions of N-substituted pyrroles

In terms of the density functional theory (DFT) using B3LYP/6-31G(d) method with full geometry optimization, gas-phase quantum chemical calculations were performed for ??-complexes formed upon the attack of electrophiles E (E = H⁺, Me⁺, Me³Si⁺, Br⁺, NO₂ ⁺, MeCO⁺, SO₃) on ??- and ??-positions of furan, thiophene, selenophene, pyrrole, and N-substituted pyrroles (NR-pyrroles, R = Me, Bu^t, SiMe₃, SiPrⁱ ₃, C₆H₄NO₂-p, SO₂Ph, CHO, COOMe) and for respective ??- and ??-substituted electrophilic substitution products. The energy differences between the ??- and ??-isomers of the ??-complexes characterize the preferred direction of the electrophilic attack, while the energy differences between the isomeric products make it possible to estimate the energy preference of a particular product. An analysis of the results obtained demonstrates the effect of the structure of heterocycle, the nature of electrophile, and thermodynamic and steric factors on the positional selectivity (??/?? ratio) in electrophilic substitution reactions of ??-electron rich five-membered heteroaromatics.     

On the reaction of 4-substituted trimethyltin aromatics with perchlorylfluoride

To evaluate the suitability of [¹⁸F]perchorylfluoride [¹⁸F]FClO₃ as an electrophilic fluorination agent for the preparation of radiopharmaceuticals, the reactivity non-radioactive FClO₃ towards 4-substituted trimethyltin aromatic compounds was studied. Contrary to the expectation, an electrophilic fluorination of the aromatic nucleus did not occur. The reaction of perchlorylfluoride with aromatic trimethylstannyl compounds resulted in the formation of trimethyltin fluoride and the respective destannylated aromatics in variable yields.     

Cyclopropyl- and Allyl-substituted Arenes in Reaction with Dinitrogen Tetroxide. Effect of Substrate Oxidation Potential on Reaction Direction

A correlation was found between oxidation potentials of acylcyclopropanes in solution (in CH₂Cl₂ and CH₃CN) and their HOMO energies calculated by semiempirical (AM1) and nonempirical (HF/6-31G and HF/6-31G**) methods. The correlation provides a possibility to forecast the reaction direction of the mentioned substrates and N₂O₄. The correlation possesses a general character. It was established for instance that arylcyclo-propanes, cyclopropylmethyl- and allylbenzenes oxidized at more positive potentials than reduction potential of NO⁺ and having more positive e_HOMOthan 9.0 eV (AM1), 8.4 eV (HF/6-31G), and 8.3 eV (HF/6-31 G**) reacted with N₂O₄ following the mechanism "electron transfer radical pair recombination" affording nitroaromatic derivatives retaining the cyclopropane (or allyl) fragments. Substrates of the same type where the electron transfer to NO⁺ should be endothermic process and whose HOMO values are less than the above critical numbers react with N₂O₄ by the mechanism of electrophilic cyclopropane ring opening (with aryl and benzylcyclopropanes) or by electrophilic addition across the double C=C bond (with allylbenzenes).     

(Aroxymethyl)trifluoro- and methyl(aroxymethyl)fluorosilanes

Conclusions (Aroxymethyl)trifluorosilanes and methyl(aroxymethyl)fluorosilanes with the general formula XC₆H₄OCH₂SiM_nF₃-n (n=0, 1) were synthesized and their reactivity with electrophilic reagents was studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2148–2150, September, 1985.     

The effect of substituents on the reactivity of aniline with phosphate radical

The reaction between aromatic amines and phosphate radical has been investigated. The reaction is accelerated by electron-releasing substituents and retarded by electron-withdrawing substituents pointing to an electrophilic attack by the PO₄^2xxx radical. σ⁺para values correlate the effect of substituents well. The rho value for PO₄^2xxx is more positive than that for CO₃^xxx indicating higher reactivity of phosphate radical towards aromatic amines than the carbonate radical.     

[Ru(DMSO)4]Cl2 catalyzes the α-alkylation of ketones by alcohols

The electrophilic α-alkylation of ketones with alcohols was accomplished by a [Ru(DMSO)₄]Cl₂ catalyzed process, water being the only wasted material. The reaction can be successfully governed to produce either the expected ketones or their related alcohols only by changing the reaction conditions. When 2-aminobenzyl alcohol was used, a cyclization process took place to yield 2,3-disubstituted quinolines.     

Comparison of reactivities of 1- and 4-oxotetrahydrocarbazoles in reactions with nucleophilic and electrophilic reagents

The half-wave potentials of polarographic reduction of the carbonyl group in unsubstituted and N-methyl- and N-phenylsulfonyl-substituted 1- and 4-oxotetrahydrocarbazoles and their reactivities in reactions with nucleophilic (NaBH₄, malonodinitrile, and cyanoacetamide) and electrophilic (DMF dimethyl acetal) reagents were compared. 4-Oxotetrahydrocarbazoles are much less reactive than 1-oxotetrahydrocarbazoles. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1832–1836, August, 2005.     

Use of Trifluoromethyl Groups for Catalytic Benzylation and Alkylation with Subsequent Hydrodefluorination

The electrophilic organofluorophosphonium catalyst [(C₆F₅)₃PF][B(C₆F₅)₄] is shown to effect benzylation or alkylation by aryl and alkyl CF₃ groups with subsequent hydrodefluorination, thus resulting in a net transformation of CF₃ into CH₂–aryl fragments. In the case of alkyl CF₃ groups, Friedel–Crafts alkylation by the difluorocarbocation proceeded without cation rearrangement, in contrast to the corresponding reactions of alkyl monofluorides.     

Regioselectivity in alkenyl(aryl)-heteroaryl Suzuki cross-coupling reactions of 2,4-dibromopyridine. A synthetic and mechanistic study

2,4-Dibromopyridine undergoes a regioselective Suzuki cross-coupling reaction at position 2 with several alkenyl(aryl) boronic acids to render 4-bromo-2-carbon substituted pyridines, difficult to be prepared otherwise, in good yields under palladium catalysis, either Pd(PPh₃)₄/TlOH or Pd₂dba₃/PCy₃/K₃PO₄ at 25 °C. This behavior is explained on the basis of the electrophilic character of both C-Br bonds, being their relative reactivity in 2,4-dibromopyridine similar to that in the corresponding monobromopyridines. In addition, the dicoupled compound 6 is not formed through a double oxidative addition of 2,4-dibromopyridine to Pd(PPh₃).     

Construction of fluorinated pyrazole derivatives via a one-pot tandem C–H insertion/electrophilic fluorination reaction

A series of 4-fluoro-pyrazole derivatives were synthesized in moderate to good yields via a one-pot tandem procedure involving an Rh₂(OAc)₄-catalyzed C–H insertion and an electrophilic fluorination with N-fluorobenzenesulfonimide (NFSI).     

Electrophilic polyfluoroalkylating agents based on sulfonate esters

This review surveys selected electrophilic polyfluoroalkylating reagents, polyfluoroalkyl alkane- and arenesulfonates, that have been used for the introduction of longer perfluorinated chains (C_nF_2n+1; n ≥ 4) with methylene, ethylene or propylene spacers into the substrate. Polyfluoroalkyl mesylates, tosylates, triflates and nonaflates are described with their applications in various syntheses of polyfluorinated compounds.     

Etude par spectrométrie de masse de l'ionisation de benzonitriles,de phénylacétonitriles et de N,N-diméthylanilines substitués

Molecular ionization potentials for series of compounds of the type X? C₆H₄? CN, X? C₆H₄CH₂? CN and X? C₆H₄? N(CH₃)₂ have been measured using the retarding potential difference technique (RPD. technique). The effect of the various substituents X is better correlated through the electrophilic Brown σ_p⁺ constants than through Hammett's σ_p values. No meta-para orientation effect is observed. For all the disubstituted phenyl compounds studied, the effect of the second substituent is affected by the electron-releasing power of the original substituent. Ionization potentials calculated by using the semi-empirical method of equivalent orbitals are in good agreement with the experimental values.     

Electronic structures and electrophilic substitution in 2-(4-R-2-quinolyl)thiophenes and 5-(4-R-2-quinolyl)-2,2′-dithienyls

The electronic structures and reactivity indexes (RI) of 2-(4-R-2-quinolyl)thiophenes and 5-(4-R-2-quinolyl)-2,2-dithienyls (R = H, COOH, COOC₂H₅, and NHCOCH₃) and their protonated forms were calculated by the Pariser-Parr-Pople (PPP) method. The peculiarities of the geometrical and -electron structures were established. The calculated reactivity indexes are compared with experimental data on the electrophilic substitution reactions of the investigated compounds. A qualitative agreement between the calculated values and the experimental data was established. It is shown that quinoline derivatives of thiophene are less reactive than the corresponding dithienyl compounds in electrophilic substitution reactions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 751–754, June, 1979.