Aminosulfenates in the electrophilic addition reactions

The reactions of methyl and ethyl diethylaminosulfenates and ethyl piperidinylsulfenate with cyclohexene and norbornene in the presence of chloro- or bromotrimethysilanes were studied.     

Gas-phase electrophilic addition reactions of chlorinated alkyl ions

Chemical ionization was used to study gas-phase electrophilic addition reactions of chloromethyl ions ([CH_xCl_3-x]⁺, x = 0, 1, 2) with a number of substituted benzenes (C₆H₅Y, Y = NH₂, OH, CHO, CN, NO₂). Mass-analyzed ion kinetic energy spectrometry was used to characterize the reaction products with respect to the site of electrophilic addition (ring v. substituent). In some cases, examination of secondary reaction products (ion–molecule adduct which has undergone an elimination reaction in the ion source) aided in establishing the original site of electrophilic addition. Aniline, benzonitrile and nitrobenzene exhibited preferential substituent interaction, while phenol and benzaldehyde gave a mixture of ring and substituent reaction products. These gas-phase results differ considerably from solution-phase Friedel–Crafts alkylation; however, they are consistent with the notion of preferential σ-bond formation at polarizable centers of negative charge.     

Phosphinates as new electrophilic partners for cross-coupling reactions

The use of enol phosphinates as electrophiles for cross-coupling reactions has been explored. Both boronic acids (Suzuki-Miyaura reaction) and stannanes (Stille reaction) couple efficiently with lactam derived phosphinates.     

Reaction of unsaturated compounds with ethyl benzenesulfenate and trimethylsilyl isothiocyanate

A new method for the synthesis of thiocyanato- and isothiocyanatoalkyl phenyl sulfides by the reaction of unsaturated compounds with ethyl benzenesulfenate and trimethylsilyl isothiocyanate has been suggested. Regio- and stereoselectivity of the reaction was studied, having taken alkenes, dienes, and alkynes as examples.     

Regioselective electrophilic substitutions of fulvenes with ethyl glyoxylate and subsequent Diels-Alder reactions

Highly regioselective electrophilic substitution of fulvenes with ethyl glyoxylate, catalyzed by EtAlCl₂ or Yb(OTf)₃ was achieved. Subsequent Diels-Alder reaction of the adduct with various dienophiles provides an efficient protocol toward highly functionalized indane and tricyclo[5.2.1.0^2,6]dec-8-ene systems.     

A new electrophilic addition to acetylenes. Synthesis of 1,2-iodofunctionalized olefins

Acetylenes react with bis(pyridine)iodo(I) tetrafluoroborate (1) in the presence of a wide variety of nucleophiles (F, Cl, Br, I, SCN, pyridine, OAc, anisole, H) to give 1,2-iodofunctionalized olefins (4).     

Stereoselectivity in the electrophilic addition reactions of stigmast-22(23)-ene derivatives

Oxidation of 5α-stigmast-22-en-3- one (1) with m-chloroperbenzoic acid afforded [22R,23R]-epoxide 3 and [22S, 23S]-epoxide 2, in a 5:3 ratio. Reaction of 1 with iodine/silver acetate gave a mixture of iodoacetates 8 and 9, which on treatment with base yielded the single epoxide 2. Those results suggest that electrophiles may preferentially approach the Δ²²-bond from the side of the 21-Me group, in accordance with observations with the ergosterol-like side chain.     

A theoretical study of electrophilic reactions

The electronic structures of protonated formyl and acetylium cations and their deprotonation paths leading to HCO⁺, COH⁺ and CH₃CO⁺have been studied by means of ab initio calculations. The results support Olah's theory that dipositive species can be the de facto reagents in electrophilic reactions.     

A quantum chemical study on electrophilic addition

Non-empirical SCF-MO calculations were carried out on two limiting structures of C₂H₄F⁺, corresponding to the cyclic and open valence tautomers, both of which are possible reaction intermediates of the electrophilic addition reaction of F₂ to CH₂ =CH₂. It was found that both species had thermodynamic stability, corresponding to two distinct minima on the energy surface. However, the 2-fluoroethyl carbonium ion showed a greater stability than the fluoronium ion by about 10 kcal/mole.     

Monoterpenoids (3-carene and α-terpinene) in electrophilic disulfide addition reactions

The reactions of 3-carene and α-terpinene with dialkyl disulfides have been studied. S. V. Kurashov Kazan' State Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 624–626, September–October, 1990.     

Ritter-type reactions of N-chlorosaccharin: a method for the electrophilic diamination of alkenes

[reaction: see text] N-Chlorosaccharin has been shown to undergo electrophilic Ritter-type reactions with alkenes in acetonitrile. The resulting labile beta-chloro sulfonylamidines can be ring-opened and cyclized to imidazolines. Overall this provides a one pot method for the electrophilic diamination of alkenes. Competing aziridine formation as well as allylic chlorination are also observed depending on the nature of the alkene used.     

The stereochemical outcome of electrophilic addition reactions on the 5,6-double bond in the spinosyns.

The electrophilic addition of reagents to the 5,6-double bond in spinosyn A and spinosyn D systems occurred with high pi-diastereofacial selectivity. Addition occurred preferentially from the beta face of the molecule with selectivities ranging from 5:1 to better than 30:1. Various NMR properties were investigated in order to distinguish the beta and alpha isomers with the help of theoretical models of the products. These NMR properties include a (13)C gamma effect to C-11 and vicinal coupling between H-4 and H-5. To help rationalize the selectivity, computational studies on the transition states for epoxidation were calculated using density functional theory. The results indicate that beta epoxidation is favored and that the geometries of the transition structures are consistent with torsional steering being the source of the selectivity.     

Superacidic activation of 1- and 3-isoquinolinols and their electrophilic reactions

Isomeric 1- and 3-isoquinolinols (11 and 12) when activated in CF(3)SO(3)H-SbF(5) acid system undergo selective ionic hydrogenation with cyclohexane to give 5,6,7,8-tetrahydro-1(2H)- and 5,6,7,8-tetrahydro-3(2H)-isoquinolinones (22 and 27). Under the influence of aluminum chloride similar products were also obtained along with 3,4-dihydro-1(2H)- and 1,4-dihydro-3(2H)-isoquinolinones (23 and 28), respectively. Compounds 11 and 12 also condense with benzene in the presence of aluminum halides, under mild conditions, to give 3,4-dihydro-3-phenyl-1(2H)- and 1,4-dihydro-1-phenyl-3(2H)-isoquinolinones (24 and 29), respectively. Prolonged reaction time or catalysis under strongly acidic HBr-AlBr(3) provides an alternative reaction pathway to yield 5,6-dihydro-6,8-diphenyl-1(2H)- and 5,6,7,8-tetrahydro-6,8-diphenyl-3(2H)-isoquinolinones (25 and 30), respectively. Products 24 and 29 were also found to revert back to 11 and 12 in the presence of aluminum halides in o-dichlorobenzene. The mechanism of these intriguing reactions, which involves superelectrophilic dicationic intermediates, is discussed.     

A new fluorimetric method for measurement of oxidase-catalyzed reactions

The oxidase-catalyzed oxidation of glucose consumes dissolved oxygen, the rate of disappearance of which is monitored by oxygen quenching of the fluorescence of pyrene in a 1:1 water—ethanol medium. The relationship between the rate of increase of fluorescence and concentration is linear for 10 μg-1 mg of glucose in the optical cell.     

A simple method for electrophilic functionalization of DNA

[reaction: see text] An extremely simple and versatile method for placing an electrophilic functional group (iodide) at the 5' end of oligodeoxyribonucleotides is described. The reaction is carried out while the protected oligodeoxyribonucleotide remains on a solid support and utilizes inexpensive iodination chemistry. We demonstrate that this reaction can be automated on a DNA synthesizer as the last step of DNA synthesis.     

A chiral reagent inducing asymmetry in electrophilic amination reactions

The chiral amination reagent (?)-$\text{1}$ was prepared from (?)-ephedrine, configurationally determined by X-ray structure analysis and reacted with carbon nucleophiles to yield the optically active amines $\text{4a-d}$ with up to 44% ee.