Superacidic activation of quinoline and isoquinoline; their reactions with cyclohexane and benzene(1)

Quinoline (1) and isoquinoline (2), upon activation by strong acids, lead to intermediate N,C-diprotonated dications, which are involved in reactions with weak nucleophiles. Thus, 1 and 2 undergo selective ionic hydrogenation with cyclohexane in CF3SO3H-SbF5, HBr-AlBr3-CH2Br2, or HCl-AlCl3-CH2Cl2 acid systems to give their 5,6,7,8-tetrahydro derivatives. They also readily condense with benzene in the presence of HBr-AlBr3 or HCl-AlCl3 to provide 5,6,7,8-tetrahydro-5,7-diphenylquinoline (10) and 5,6,7,8-tetrahydro-6,8-diphenylisoquinoline (12), respectively.     

Superacidic and HUSY-zeolite activation of 1,3-indandione: reactions with benzene and cyclohexane

1,3-Indandione (1) readily condenses with benzene and undergoes selective ionic hydrogenation with cyclohexane when activated by superacids, such as CF₃SO₃H, AlCl₃ and AlBr₃ to give 3,3-diphenyl-1-indanone (4) and 1-indanone (7), respectively. Combination of these reactions in ‘one-pot’ yields 3-phenyl-1-indanone (5). In addition, similar reactions have been carried out using the regenerable solid acid, HUSY-zeolite, providing an effective excess of acidic sites. The mechanism of these reactions, with potential involvement of superelectrophilic dicationic intermediates, is discussed.     

3-(1,3-dioxobutan-1-yl)-2H-chromen-2-one in reactions with electrophilic and nucleophilic reagents

Reactions of 3-(1,3-dioxobut-1-yl)-2H-chromen-2-one with electrophilic (boron trifluoride diethyl etherate and phosphorus pentachloride) and nucleophilic (phosphorus pentasulfide and hydrogen sulfide) compounds have been studied. The reactions proceed mainly with the enol form of the substrate which is more stable both in polar and nonpolar solvents. The substrate ability to undergo aromatization into 4-oxopyranochromolium salts under action of electrophilic reagents and thionation at the oxo groups have been demonstrated. The suggested schemes of heterocyclization have been described. Possibility of in situ competitive formation of the hemiketal at the interaction with hydrogen sulfide in acidic medium has been found.     

Intramolecular sulfoxide electrophilic sulfenylation in 1- and 3-acylindoles

Heating 1-(2-ethylsulfinyl)benzoylindole (1) in refluxing p-xylene [thermal Sulfoxide Electrophilic Sulfenylation (SES)] produces indolo[2,1-b][1,3]benzothiazin-12-one (2) in 66% yield. Similar treatment of 1-methyl-3-(2-ethylsulfinyl)benzoylindole (8) provides three products: sulfide 7 and cyclized products 9 and 10 in 10, 19 and 15% yield, respectively. Conversion of 10 to 9 under the reaction conditions is demonstrated and a spirocyclic intermediate 12 , which may form from both 9 and 10 but undergoes only preferential S-migration, is postulated to account for the rearrangement.     

Preparation of trifluoromethylated ynamines and their reactions with some electrophilic reagents

N,N-Dialkyl(3,3,3-trifluoro-1-propynyl)amines were prepared by a three-step procedure starting from commercially available 2,2,3,3,3-pentafluoropropanol. The reactions of these trifluoromethylated ynamines with some electrophiles, such as aldehydes, halogens or N-halosuccinimides (NXS), were investigated. The fluorinated ynamines reacted with aldehydes in the presence of a catalytic amount of Lewis acid to provide the corresponding α-(trifluoromethyl)-α,β-unsaturated amides in good to excellent yields with high Z-stereoselectivity. These ynamines reacted with molecular bomine to give, after treatment with sodium hydrogen carbonate, N,N-dialkyl-2-bromo-3,3,3-trifluoropropanamides in good yields. The reaction with an equimolecular amount of NXS in aqueous acetonitrile also gave the corresponding 2-halo-3,3,3-trifluoropropanamides in good to excellent yields. On the other hand, the reaction of the ynamine with NXS in anhydrous acetonitrile led to the formation of the addition products in high yields. Upon treating the addition products with an equimolecular amount of NX′S in aqueous acetonitrile, the corresponding 2,2-dihalo(X,X′)-3,3,3-trifluoropropanamides were produced in nearly quantitative yields.     

Superacidic low-temperature cyclization of terpenols and their acetates

The superacidic low-temperature cyclization of terpenols and their acetates by fluorosulfonic acid represents a highly efficient chemo- and structurally selective and stereospecific process. Homoallylic alcohols (-isomers of cycloterpenols) are the products of cyclization of terpenols; the configuration of the hydroxymethyl group in the products is predetermined by the configuration of the allylic double bond in aliphatic or partially cyclized precursors. The cyclization of terpenyl acetates yields monoacetates of fully cyclized diastereomeric primary-tertiary -diols. Their stereochemistry also depends on the configuration of the allylic double bond in the starting substrates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2494–2506, December, 1995.     

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.     

2-(2-Furyl)-1(3)H-imidazo[4,5-f]quinoline. Synthesis and electrophilic substitution reactions

2-(2-Furyl)-1(3)H-imidazo[4,5-f]quinoline was synthesized by the Weidenhagen reaction of quinoline-5,6-diamine with furfural. Its alkylation with methyl iodide in the system KOH-DMSO gave two isomeric N-methyl derivatives, 2-(2-furyl)-1-methyl-1H- and 2-(2-furyl)-3-methyl-3H-imidazo[4,5-f]quinolines, the latter prevailing. 2-(2-Furyl)-3-methyl-3H-imidazo[4,5-f]quinoline was brought into electrophilic substitution reactions: bromination, nitration, formylation, acylation, sulfonation. Depending on the reaction conditions, electrophilic attack could be directed at both furan ring and quinoline fragment.     

Generation and electrophilic substitution reactions of 3-lithio-2-methyleneaziridines

2-Methyleneaziridinyl anions can be produced by selective deprotonation of the parent aziridine at C-3 using sec-BuLi/TMEDA. Subsequent reaction with a wide variety of electrophiles including MeI, ICH₂CH₂CH₂CH₂Cl, PhCH₂Br, allyl bromide, Me₃SiCl, Bu₃SnCl, PhCHO and Ph₂CO provides the corresponding C-3 substituted derivatives in moderate to good yields (43-91%). In the case of homochiral methyleneaziridines bearing an (S)-α-methylbenzyl group on nitrogen, high levels of diastereocontrol (up to 90%de) can be achieved in this lithiation/alkylation sequence.     

Superacidic cyclization of higher terpenoid acids and their esters

The superacidic cyclization of aliphatic and partially cyclized C₁₅–C₂₅ terpenoid acids and their esters proceeds structure-selectively and stereospecifically, affording -isomers of completely cyclized epimeric ,-unsaturated acids or esters; the configuration of their carboxylic or ester groups is predetermined by the configuration of the double bond conjugated with the carboxyl or ester groups in the starting compounds.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2507–2513, December, 1995.     

Alkali metal 2-(1-adamantyl)ethynethiolates: Synthesis and reactions with electrophilic reagents

Treatment of ethyl 2-[1-(1-admantyl)ethylidene]hydrazine-1-carboxylate with thionyl chloride gave 4-(1-adamantyl)-1,2,3-thiadiazole which readily underwent decomposition by the action of strong bases with formation of alkali metal 2-(1-adamantyl)ethynethiolates. The latter were brought into reactions with proton donors and benzyl halides.     

Study of some electrophilic reactions of 6-hydroxy (methoxy)-2-benzyl-3-hydroxypyridines

Conclusions A study was made of the effect of the benzyl group on the reactivity and the orientation of aromatic substitution in the 6-hydroxy(methoxy)-2-benzyl-3-hydroxypyridines and their N-oxides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 206–209, January, 1973.     

A new method for the activation of ethyl benzenesulfenate in electrophilic addition reactions

Reactions of unsaturated compounds with the PhSOEt-SOHal₂ and PhSOEt-Me₃SiHal systems (Hal = Cl or Br) were proposed as a new route to haloalkyl phenyl sulfides. With acyclic and mono- and bicyclic alkenes and dienes as examples, the regio- and stereoselectivity of the reactions were studied.     

2-(2-Furyl)-5,6-dihydro-1(3)H-acenaphtho[4,5-d]imidazole. Synthesis and electrophilic substitution reactions

2-(2-Furyl)-5,6-dihydro-1(3)H-acenaphtho[4,5-d]imidazole was synthesized by the Weidenhagen reaction of acenaphthene-4,5-diamine with furfural. Alkylation of the title compound with methyl iodide in KOH-DMSO gave isomeric 1- and 3-methyl derivative, the latter being the major product. 2-(2-Furyl)-3-methyl-5,6-dihydro-3H-acenaphtho[4,5-d]imidazole was subjected to electrophilic substitution reactions (bromination, nitration, formylation, acylation, and sulfonation. Depending on the conditions, electrophilic attack was directed at the furan ring or acenaphthene fragment or both these.     

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.     

Cycloisomerization of omega-aryl-1-alkynes: GaCl3 as a highly electrophilic catalyst for alkyne activation

Cycloisomerization of a variety of omega-aryl-1-alkynes, where omega = 5 or 6, in the presence of a catalytic amount of GaCl3 provided dihydronaphthalene derivatives or dihydrobenzocycloheptenes, respectively, in high yields.