Amidinosulphenylation of alkenes

Phenylsulphenamides react chemoselectively with an alkene and a nitrile in the presence of trifluoromethanesulphonic acid to give $\text{N}$-(β-phenylthioalkyl) amidines; in the absence of nitrile an amine is formed.Regioselective 1,2-difunctionalization of alkenes with a nitrogen nucleophile and an alkylthio^1?3 or alkylseleno^1,4 group has attracted a good deal of interest recently, because it presents a simple answer to the lack of nitrogen electrophiles capable of attacking a weak nucleophile such as an alkene.⁵ Reductive or oxidative elimination of the RS(e) group leads to overall addition to or substitution at the alkene by the nitrogen nucleophile (“N”) respectively (Scheme 1).     

Silylmetalation of alkenes

Silylmetalation of alkenes is challenging due to the low reactivity of the substrates. In contrast, carbometalation of alkenes has been realized through several innovative methods, including activation of the reagent and the substrate. A similar approach could be applicable to silylmetalation of alkenes, and we have recently developed a bimetal activation method using zincate complexes for this purpose. Here, we describe how the silylzincation of alkenes was achieved. First, the strategies for carbometalation of alkenes will be summarized. Secondly, the history and development of silylzincation chemistry are briefly described. Then the details of our findings related to two types of silylzincation of alkenes, as well as recent progress in mechanistic studies, are discussed. The key point in the silylzincation of alkenes proved to be the bimetal activation of the substrate. One metal (copper or titanium) strongly coordinates and activates the alkene moiety, and the other metal (zinc) acts as the electron acceptor from the silyl group by way of the alkene moiety. This dual activation concept is expected to be applicable to other combinations of metals, as well as to new types of reactions.     

Iodine-catalyzed disulfidation of alkenes

The disulfidation reactions of alkenes with disulfides were thoroughly investigated in this paper. Using H₂O or DCE as the solvent, most reactions occurred smoothly to give the corresponding disulfidated products in good to high yields at room temperature within 12 h.     

Enthalpimetry of non-aromatic alkenes

A method of increased sensitivity for hydrogen enthalpimetry of olefins in mumole quantities is reported. The method depends on a linear relationship between the amount of alkene present and the heat given off on hydrogenation at slightly more than 2 atm pressure over palladium catalyst on charcoal. Least-squares analysis of the results shows that the measured heat effect is a linear function of amount of alkene taken, with a relative standard deviation of 1-3% for samples ranging in size from 1.4 to 37.5 mumole. Extension of the method to samples in submicromolar quantities was only partially successful; in a series of measurements extending to a minimum amount of 0.64 mumole, the relative standard deviation rose to 9.6%.     

Transition-metal-free trifluoromethylaminoxylation of alkenes

No transition metal! Fluorinated hypervalent-iodine reagents react with TEMPONa in the presence of an alkene under mild conditions to give the corresponding perfluoroalkylaminoxylation products. These radical addition/trapping reactions occur with high stereoselectivity using commercially available reagents, and the product alkoxyamines are readily transformed into the corresponding alcohols.     

Iodine-mediated acyloxyselenenylation of alkenes

In the presence of I₂, an acyloxyselenenylation of alkenes with diselenides and carboxylic acids is developed. This metal-free iodine-mediated acyloxyselenenylation proceeds efficiently under mild reaction conditions, affording a series of 2-acyloxy-1-selenides with high regioselectivity and in moderate to good yields.     

过渡金属催化下的烯烃硼氢化反应

本文综述了在过渡金属尤其是铑络合物催化下烯烃与CB ( 邻苯二酚硼烷 ) 的硼氢化反应在化学、位置和立体选择性的进展, 对它们的机理也进行了讨论。     

Cobalt-catalyzed dimerization of alkenes

In the presence of CoX₂(PPh₃)₂/3 PPh₃ and zinc metal conjugated alkenes (CH₂CHCOOR, CH₂CHCN, CH₂CHSO₂Ph and CH₂CHCONEt₂) undergo reductive tail-to-tail dimerization to yield the corresponding saturated linear products. Under similar reaction conditions, vinylarenes (ArCHCH₂) give stereoselective head-to-tail dimerization products, trans-1,3-diarylbut-1-ene, in good to excellent yields.     

Anodic oxidation of sodium-O-cyclohexylphosphonite

The research data on the anodic oxidation of sodium salt of cyclohexyl ester of hypophosphorous acid on a Pt electrode are shown. The molecule of this salt has two electroactive centers: phosphoryl (PONa) and phosphine (P-H).     

Anodic fluorination of azobenzene

Electrolysis of azobenzene (I) in the system of Et₄NF · 3HF, MeCN results in predominant fluorination of the products of polymerization of I formed in the course of electrolysis. Also, m-fluoroazobenzene (II) and o-fluoroazobenzene (III) (II: III = 4: 1) were obtained with a low yield. Anomalously high content of m-isomer II is probably related to redistribution of localization of electron-deficient centers in cation-radical I as a result of its protonation by acidic electrolyte.     

Intrazeolite photooxidations of electron-poor alkenes

The inability of the intrazeolite environment to influence the regiochemistry of addition of singlet oxygen to electron-poor olefins is reported. This divergent behavior with respect to electron-rich alkenes is rationalized with a multicomplexation model that emphasizes the importance of intrazeolite substrate-cation binding.     

Catalyst-free fluorinative alkoxylation of alkenes

The fluorinative alkoxylation of simple alkenes under catalyst-free conditions was achieved. Various substituted olefins, including terminal and internal alkenes, and oxygen-containing nucleophiles were compatible with the standard conditions, and gave a variety of β-fluoroethers in good to excellent yields. Notably, the alkynyl and chloride-containing nucleophiles were well tolerated. In addition, acetic acid and TsNH₂ could be also used as nucleophiles and successfully afforded the desired products in good yields.     

Regioselective aminobromination of terminal alkenes

The addition of t-butyl N,N-dibromocarbamate (BBC) to a variety of terminal alkenes has been studied. The reaction was spontaneously initiated and proceeded smoothly in refluxing dichloromethane. The N-bromo adducts, formed upon addition, could be reduced in situ with aqueous sodium sulfite to give the corresponding 2-bromo-N-Boc-amines. Immediate deprotection of these compounds with gaseous HCl or p-toluenesulfonic acid afforded 2-bromoamine hydrochlorides or tosylates in pure state and good overall yields. The observed regioselectivity for anti-Markovnikov addition, as proven by NMR and MS, is fully consistent with the radical-chain mechanism proposed for the reaction.     

Copper-catalyzed intermolecular hydroamination of alkenes

[reaction: see text] Regioselective additions of arylsulfonamides to vinylarenes, norbornene, and cyclohexadiene were achieved using a copper-diphosphine catayst under mild reaction conditions. These processes appear to be ligand-accelerated.     

Organocatalytic diastereoselective dibromination of alkenes

A highly diastereoselective pyrrolidine-promoted dibromination of alkenes by combination of NBS and succinimide is presented. The pyrrolidine-mediated dibromination of alkenes is higly anti-selective and gives the corresponding products in moderate to high yields and up to >25:1 dr.     

First osmium-catalysed ketamination of alkenes

Conditions for a first oxidative conversion of alkenes into 2-amino ketones are described, which yield racemic products within a direct oxidation pathway and 2-amino ketones with up to 99% enantiomeric excess from the corresponding enantiopure amino alcohols.