Iodination of nitroarenes by a superactive reagent based on iodine chloride

Iodine chloride reacts with Ag₂SO₃ in H₂SO₄ to give a new superelectrophilic reagent capable of iodinating nitrobenzene, halogenated nitrobenzenes, nitrotoluenes, and aromatic compounds with two nitro groups in the ring. Mononitroarenes are easily iodinated at 0–20°C, while dinitroarenes require heating to 100–170°C. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1303–1306, July, 1999.     

Direct electrophilic N-trifluoromethylation of azoles by a hypervalent iodine reagent

Effective CF(3) transfer: Various electron-rich nitrogen heterocycles (pyrazoles, triazoles, and tetrazoles) can be directly N-trifluoromethylated by a hypervalent iodine reagent in an efficient manner. The optimized procedure, which includes an in situ silylation of the substrate followed by an acid-catalyzed CF(3) transfer, provides ready access to a series of new and previously challenging or inaccessible NCF(3) compounds.     

Aspects of stereoselectivity in electrophilic addition reactions of iodine with 5-allenyl-2,3,5-trichloro-4,4-dimethoxycyclopent-2-en-1-one and its derivatives

The reactions of 5-allenyl-2,3,5-trichloro-4,4-dimethoxycyclopent-2-en-l-one and related compounds with I₂ were studied. The stereochemistry of the resulting 1,2-adducts with I₂ at the terminal double bond of the allenic fragment depends in a complex way on the character of functionalization in the cyclopentene fragment of the starting molecule.     

Inorganic reactions of iodine(+1) in acidic solutions

We present a thorough analysis of the former works concerning the hydrolysis of iodine and its mechanism in acidic or neutral solutions and recommend values of equilibrium and kinetic constants. Since the literature value for the reaction H₂OI⁺ ? HOI + H⁺ appeared questionable, we have measured it by titration of acidic iodine solutions with AgNO₃. Our new value, K(H₂OI⁺ ? HOI + H⁺) ～ 2 M at 25°C, is much larger than accepted before. It decreases slowly with the temperature. We have also measured the rate of the reaction 3HOI → IO₃^? + 2I^? + 3H⁺ in perchloric acid solutions from 5 × 10^?2 M to 0.5 M. It is a second order reaction with a rate constant nearly independent on the acidity. Its value is 25 M^?1 s^?1 at 25°C and decreases slightly when the temperature increases, indicating that the disproportionation mechanism is more complicated than believed before. An analysis of the studies of this disproportionation in acidic and slightly basic solutions strongly supports the importance of a dimeric intermediate 2HOI ? I₂O·H₂O in the mechanism. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36:480–493, 2004     

氟烷基化与氟烷氧基化的研究——25.甲酸/三乙胺引发氟烷基碘对烯烃的加成

氟烷基碘对烯烃的催化加成,是将氟烷基引入碳氢化合物的有效途径。通常利用光照和自由基引发来实现。最近我们发现许多金属     

系统论述烯烃亲电加成反应的立体选择性

亲电加成是烯烃最具代表性的典型反应,在本科的教学中,要求学生熟练掌握和应用。烯烃的亲电加成反应不仅涉及到反应的活性、区域选择性问题,还涉及到反应的立体选择性问题。但对于立体选择性的阐述,很多教科书并不全面,甚至不够严谨,因而在教学过程中发现学生在理解这部分内容时存在一定的误解。针对这一问题进行了系统的论述,以帮助学生更好更正确地理解和掌握烯烃的亲电加成反应的立体选择性。     

Synthesis of di(2-bromoalkyi) disulfides by electrophilic addition of dithiobisamines to olefins

A new method for the synthesis of di(2-haloalkyl) disulfides and ,'-dibromothiacyclanes was proposed based on reactions of dithiobisamines with olefins in the presence of PBr₃, PBr₅, or POBr₃. Reactions with alkenes lead to di(2-bromoalkyl) disulfides. Analogous products and heterocyclic dibromosulfides,i.e., the products of addition of one dithiobisamine molecule to both double bonds of a diene, are obtained in reactions with alkadienes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2511–2525, October, 1996.     

New Derivatives of 1,2-Alkadienephosphonic Acids

Abstract

The preparations of new cyclic derivatives of 1,2-alkadienephosphonic acids have been reported and the reactions of these compounds with bromine have been investigated.     

Iodosulfenylation of olefins with sulfenamides in the presence of metal iodides

Reactions of arylsulfenamides, arylsulfenates, thiobisamines, and dithiobisamines with olefins in the presence of zinc, tin(ii), tin(iv), antimony(iii), or magnesium iodides were investigated. In the case of cage olefins, the reactions afford mixtures of 1,2-iodosulfides and diiodides, the ratio between which depends on the type of iodine-containing Lewis acid. lodosulfides were obtained in the highest yields in the reactions of cage olefins upon activation with zinc or tin(ii) iodides. In the case of olefins prone to the Wagner—Meerwein rearragement (bicyclo[2.2.1]heptanes) or to the addition—elimination reaction (camphene), the corresponding products formed. A reaction mechanism is proposed. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1569–1582, September, 2000.     

New 1-hetarylfuropyridines and chromenes based on pyridoxal and 4-hydroxycoumarin

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Direct iodination of 3- and 4-nitropyrazoles with a reagent based on iodine monochloride and silver sulfate

The reagent obtained from iodine monochloride and silver sulfate in sulfuric acid easily iodinates I-methyl-3-nitropyrazole under mild conditions to give 4-iodo or 4,5-diiodo derivatives, 1-Methyl-4-nitropyrazole was also directly iodinated with this reagent for the first time. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1482–1484, August, 2000.     

Synthesis and Chemical Behavior of N-(2-Chloroethyl)O-alkyl-3-methyl-1,2-butadienephosphoniates

Abstract

The synthesis and reactivity of the titled compounds towards electrophilic reagents have been discussed.     

Intramolecular electrophilic aromatic substitution of α-alkylcinnamaldehydes affording 1-alkoxy-2-alkylindenes

Treatment of α-alkylcinnamaldehydes with orthoesters, alcohols, or thiols in the presence of BF₃·OEt₂ induces an intramolecular electrophilic aromatic substitution reaction to afford 1-alkoxy-2-alkylindenes. The reaction mechanisms of the indene formation have been elucidated on the basis of the reaction behaviors of β-deuterated α-methylcinnamaldehyde and the NMR studies of the reaction mixture. The transformation process involves successive reactions, i.e., alkoxylation of the carbonyl carbon of α-alkylcinnamaldehydes to form acetals, elimination of alkoxide from the acetals to give alkoxycarbenium ion and γ-alkoxyallyl cation, and intramolecular electrophilic arylation to afford the indene ring structure.     

New Catalytic Approaches towards the Enantioselective Halogenation of Alkenes

The addition of electrophilic reagents to the carbon–carbon double bond is one of the most fundamental reactions in organic chemistry. Halogen electrophiles constitute probably the most important class of electrophiles and have been widely used to induce electrophilic addition reactions to alkenes like halolactonizations or dihalogenations. Despite their long history and high importance, catalytic, asymmetric variants of these reactions have been underdeveloped until very recently. During the last two years this has changed and many novel approaches have been reported. This review aims to cover these new developments through discussing the common themes as well as the suggested mechanistic scenarios.     

Intramolecular electrophilic rearrangements in saturated acyclic systems. Reactions of bis-carbanions with isocyanates

The reactions of mono- and bis-isocyanates with bis-carbanions whose COOAlk groups at the anionic centers do not contain acidic hydrogen atoms proceed unusually to form bis-carbamates (including oligomeric carbamates) due to migration of the alkoxycarbonyl groups from the carbon to the nitrogen atom.     

Si-C-Bond cleavage in 1-organylsilatranes by bromine or iodine chloride

The Si-C bond in I-organylsilatranes is cleaved by bromine or iodine chloride to yield 1-bromo- or 1-chlorosilatrane respectively. In the presence of Et2O or THF and under the action of dioxane dibromide, I-halosilatraneTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2075–2077, August, 1996.