Evidence for single electron transfer in the reaction of alkoxides with alkyl halides

Evidence for a radical process in the reaction of lithium alkoxides with alkyl iodides was obtained by the observation of cyclization of appropriate radical probes, by the trapping of radicals, and by EPR spectroscopic observations relating to the one electron donor properties of alkoxides.     

Carbon radical addition to N-sulfonylimines mediated by triethylborane or zinc

The utility of N-sulfonylimines as radical acceptors was investigated under the different reaction conditions such as the stannyl radical-mediated addition reaction, the triethylborane-mediated tin-free radical reaction, and the zinc-mediated aqueous-medium radical reaction. The alkyl radical addition reaction of N-sulfonylimines proceeded effectively without the activation by Lewis acid. These reactions were successfully extended to one-pot reactions for preparing a wide range of amine derivatives.     

Evidence for single electron transfer in metal-halogen exchange. The reaction of organolithium compounds with alkyl halides.

The reaction of $\text{t}$-BuLi with cyclizable 1° and 2° alkyl halide radical probes at low temperature produced stab]e cyclized and uncyclized organolithium products as well as cyclized hydrocarbons which clearly indicate the presence of radical intermediates during the course of these reactions.     

The reaction of carbanions with 2-substituted-2-nitropropanes : Substitution and dimerization occurring by radical chain processes involving electron transfer

The reaction of mono-enolate anions with O₂NCMe₂X where X = Cl, NO₂, p-MePhSO₂ yield coupling (RCOCH(R′)(CMe₂NO₂) and enolate dimerization products (RCOCH(R′)CH(R′)COR) by free radical chain mechanisms involving bimolecular substitution or electron transfer reactions between the enolate anion and the intermediate nitro alkane radical anion (XCMe₂NO₂^?).     

Spectroscopic evidence for the reduction of alkyl halides by metal hydrides via a single electron transfer mechanism

This report provides spectroscopic evidence to support a single electron transfer pathway to describe the reaction of metal hydrides with alkyl halides by direct EPR observation of the radical formed in the reaction.     

Ultrasound-assisted addition of alcohols to N-acyliminium ions mediated by In(OTf)3 and synthesis of 1,2,3-triazoles

An easy and mild approach using ultrasound-assisted reaction addition of alcohols to N-acyliminium ion mediated by Lewis acid, In(OTf)₃, allowed the synthesis of ether pyrrolidinones; next, the products were converted to 1,2,3-triazoles using click chemistry reaction conditions. The products in both reactions were afforded in moderate to good yields.     

Radical addition of alkyl halides to formaldehyde in the presence of cyanoborohydride as a radical mediator. A new protocol for hydroxymethylation reaction

Hydroxymethylation of alkyl halides was achieved using paraformaldehyde as a radical C1 synthon in the presence of tetrabutylammonium cyanoborohydride as a hydrogen source. The reaction proceeds via a radical chain mechanism involving an alkyl radical addition to formaldehyde to form an alkoxy radical, which abstracts hydrogen from a hydroborate anion.     

Free radical SH2′ reaction mechanism study by comparing free radical SH2′ reaction with free radical addition reaction

It is not clear whether the mechanism of the S_H2′ reaction of allyl chloride is concerted or stepwise. The relative rates of the competitive free radical addition to two different double bonds in (2-chloroallyl)-(2-choromethylallyl) ether have been determined. There are two competitive free radical addition reactions, one is free radical S_H2′ reaction and the other is free radical addition reaction. The mechanism of the S_H2′ reaction is discussed by comparing free radical S_H2′ reaction with free radical addition reaction.     

Reaction of ferrocenecarbothioamide and N-(ethoxycarbonyl)ferrocenecarbothioamide with alkyl halides

Reaction of ferrocenecarbothioamide and N-(ethoxycarbonyl)ferrocenecarbothioamide with alkyl (mainly benzyl) halides in the presence of K₂CO₃ has been studied. The former compound yielded cyanoferrocene in high yield whereas the latter was transformed into the corresponding thioimidates as a result of S-alkylation and deprotonation. The molecular structure of S-p-nitrobenzyl-N-(ethoxycarbonyl)-ferrocenethioimidate was determined by single-crystal X-ray analysis and revealed the E configuration. The plausible reaction mechanism is discussed.     

New fused dithiabicyclic compounds from the reaction of N,N-dialkyl perfluorothioamides with allylmagnesium halides

Allylmagnesium reagents react with N,N-dialkylperfluorothioamide to give, at low temperature, an adduct stable enough to be trapped. At room temperature, this adduct can evolve by elimination of either a sulfide salt, leading to an iminium intermediate, and then an N,N-dialkyl-α,α-bis(allyl)-α-perfluoroalkylamine. This process is favoured if an excess of allyl magnesium is used. Alternatively, the adduct eliminates an aminyl moiety giving allyl(perfluoroalkyl)thioketone which is converted in situ into an unprecedented fused bis(perfluoroalkyl) bis(dihydrothiopyrane). A sequence deprotonation of the thioketone - oxidation of the resulting dienethiolate - dimerization of the dienethiyl radical is proposed to rationalize the formation of this unexpected bicyclic compound.     

Effect of electrostatic field on the polymer chain in the quaternized reaction of polyvinylpyridine with alkyl halides

In order to discuss the electrostatic-field effect on a polymer reaction, the quaternization of poly-4-vinylpyridine–benzyl chloride (system I) was compared to that of poly-γ-chloromethylstyrene–γ-picoline (system II). In these two systems, the reaction initially proceeded according to the simple second-order kinetics. However, after the degree of quaternization exceeded 20–30 mole-%, a deviation from simple second-order kinetics occurred. In system I negative deviation occurred, while in system II positive deviation occurred. These phenomena occurred even though the solvent or the initial concentrations of the reactants were changed. The reasons for these phenomena are given below. In system I, the quaternized pyridine nitrogens prevented the benzyl chloride from approaching the unquaternized pyridine nitrogens. However, in system II the free γ-picoline was attracted by the quaternized chloro-γ-methyl site. Furthermore, the point at which the deviation occurred was determined by the degree of chloromethylation. All these results suggest that the effect of an electrostatic field must be presumed in these two systems.     

Intermolecular atom transfer radical addition to olefins mediated by oxidative quenching of photoredox catalysts

Atom transfer radical addition of haloalkanes and α-halocarbonyls to olefins is efficiently performed with the photocatalyst Ir[(dF(CF(3))ppy)(2)(dtbbpy)]PF(6). This protocol is characterized by excellent yields, mild conditions, low catalyst loading, and broad scope. In addition, the atom transfer protocol can be used to quickly and efficiently introduce vinyl trifluoromethyl groups to olefins and access 1,1-cyclopropane diesters.     

The question of the validity of using radical probes for determining SET. The reaction of alkyl halides with LiAlH4.

The validity of using a cyclizable alkyl iodide as a radical probe on reaction with LiAlH₄ and other nucleophiles has been recently questioned. Both previously presented data as well as new data presented here makes it clear that the cyclized products formed in the reactions studied are indeed formed to a significant extent via an electron transfer process involving a radical precursor.