A concise and optimized four-step approach toward 2-(aryl-)alkylsulfanyl-, 4(5)-aryl-, 5(4)-heteroaryl-substituted imidazoles using alkyl- or arylalkyl thiocyanates

A convenient cyclization method leading to trisubstituted imidazoles in up to 84% yield is reported. Diverse 1-aryl-, 2-heteroaryl-substituted ethanones are converted into the corresponding α-oximino derivatives which are reduced under regioselective conditions. The obtained α-amino carbonyl intermediates are reacted with alkyl- or arylalkyl thiocyanates to directly yield C²-S-substituted imidazoles.     

Activity and selectivity in the electrophilic substitution of five-membered heterorings (review)

Data on the activity and selectivity in reactions involving the electrophilic substitution of five-membered heteroaromatic compounds with one heteroatom are discussed. Chief attention is directed to the reactions of pyrrole, furan, thiophene, and their substituted derivatives. The inconsistency in the change in the activity (reaction rate) — N>O>S — and in the positional selectivity (the ß ratio) — N相似文献   

Study of electrophilic substitution and oxidation reactions of 4- and 5-hydroxybenzo-2,1,3-selenadiazoles

The halogenation, nitrosation, and oxidation of 4- and 5-hydroxybenzo-2,1,3-selenadiazoles have been studied, as has the acetylation of these hydroxy compounds and their halogen and nitroso derivatives. The structure of the resulting compounds has been demonstrated, and it has been found that the nitroso-substituted derivatives exist primarily in the tautomeric oxime form.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1135–1140, August, 1992.     

Stereochemistry of electrophilic substitution in β-lactam systems (review)

The literature data on the synthesis of 3-monosubstituted and 3,3-disubstituted -lactams on the basis of reactions of lithium derivatives of 2-azetidinones with electrophiles are systematized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. d9, pp. 1155–1171, September, 1990.     

Palladium-phosphinous acid-catalyzed cross-coupling of aryl and acyl halides with aryl-, alkyl-, and vinylzinc reagents

Several palladium-phosphinous acids have been prepared and employed in cross-coupling reactions of aryl or acyl halides with aliphatic and aromatic organozinc reagents. The POPd7-catalyzed reaction of aryl halides, including electron-rich aryl chlorides, and arylzinc reagents was found to afford biaryls exhibiting alkoxy, alkylthio, amino, ketone, cyano, nitro, ester, and heteroaryl groups in 75-93% yield. Excellent results were obtained with sterically hindered substrates which gave di- and tri -ortho-substituted biaryls in up to 92% yield. Aryl halides also undergo POPd7-catalyzed aryl-vinyl and aryl-alkyl bond formation under mild conditions. Styrenes and alkylarenes were prepared in 79-93% yield from aryl halides and vinyl or alkylzinc reagents. The replacement of aryl halides by acyl halides provides access to ketones which were produced in up to 98% yield when POPd was used as catalyst. This approach overcomes the limited substrate scope, reduced regiocontrol, and low functional group tolerance of traditional Friedel-Crafts acylation methods.     

Mild electrophilic trifluoromethylation of secondary and primary aryl- and alkylphosphines using hypervalent iodine(iii)-CF(3) reagents

A direct, mild and efficient trifluoromethylation of primary and secondary phosphines is achieved with easily accessible, cheap hypervalent iodine compounds acting as electrophilic CF(3)-transfer reagents.     

A rapid synthesis of asymmetric alkyl- and aryl-2,9-disubstitued 1,10-phenanthrolines

The finding that alkyl- and aryllithium reagents add almost instantly to the N-C2/C9 bond of 1,10-phenanthrolines led us to the development of a reaction scheme where the C2 and C9 positions of 1,10-phenanthroline can be functionalized by two different alkyl or aryl groups in a one-pot reaction. Furthermore, the total synthetic and work-up time needed for the entire transformation from unsubstituted 1,10-phenanthrolines into asymmetric 2,9-disubstituted 1,10-phenanthrolines was under 2 h and produced very high yields.     

First example of aromatic electrophilic substitution using selenium(II) chloride

Russian Journal of Organic Chemistry -     

Bisindoles. 18. Some electrophilic substitution reactions in the 1,2-di(indol-5-yl)ethane series

A quantum-chemical calculation has been made and the laws of the electron-density distribution in the molecule of 1,2-di(indol-5-yl)ethane have been determined. The electrophilic substitution reactions most characteristic for it have been studied.For communications 15–17, see [1–3].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 73–77, January, 1984.     

Basicity and structure of 5-hydroxybenzimidazoles in nitromethane

Examination of the acid-base properties of 5-hydroxybenzimidazoles has shown them to exist in nitromethane as the 5-hydroxy-tautomers. Substituents in the 2-position have a predominantly inductive effect on the basicity of the 3-nitrogen, rationalized as in other nitrogen heterocycles by the proximity of the substituents to the reaction center.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. The Research Institute for Intermediates and Dyes, 103787 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 421–425, February, 1992.     

Synthesis of 5-heteroarylazulenes: first selective electrophilic substitution at the 5-position of azulene

1,3-Di-tert-butylazulene reacted with highly electrophilic trifluoromethanesulfonate of N-containing heterocycles to give 5-(dihydroheteroaryl)azulene derivatives in good yield and treatment of the 5-(dihydroheteroaryl)azulene derivatives with KOH afforded 5-(heteroaryl)azulenes in excellent yield.     

Synthesis and electrophilic substitution reactions of 2-aryl-3,4-bis(carbomethoxy)furans

The thermal decomposition of the products of hydrogenation of the adducts obtained from arylfurans and dimethyl acetylenedicarboxylate leads to the formation of 2-aryl-3,4-bis(carbomethoxy)furans. The bromination of these compounds takes place in the 5 position of the furan ring; depending on the concentration of the nitric acid used, nitration leads to the formation of products of nitration in both the furan and the benzene rings.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 453–456, April, 1982.     

Behavior of 6-cyclopropyl- and 6-bromo-7-cyclopropyl-1,4-benzodioxanes under electrophilic substitution reaction conditions

Bromination of 6-cyclopropyl-1,4-benzodioxane occurs with concerted orientation of the ethylenedioxy group and the cyclopropyl radical for the least sterically hindered position of the aromatic ring. Nitration of 6-bromo-7-cyclopropyl-1,4-benzodioxane does not lead to products of substitution of the hydrogen atom in the 5 or 8 position of the 1,4-benzodioxane, but rather to the nitrodebromination product: 7-nitro-6-cyclopropyl-1,4-benzodioxane. The anomalous behavior of the bromo-substituted benzodioxane is explained by the predisposition of the carbon atom bonded to the bromine towardipso attack by an electrophile.M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 618–620, May, 1998.     

Retrieval and analysis of transition states in electrophilic substitution reactions of the carborane(12) series

The transition states of the reaction of electrophilic substitution in a series of ortho-, meta-, and para-carboranes were found by calculations in the B3PW91/6-31G(d,p) and B3LYP/6-31G(d,p) approximations. The key role of catalyst was demonstrated in the reactions of halogenation and alkylation. The reaction selectivity of electrophilic alkylation by CH₃Br in the presence of AlCl₃ should be lower than that of the chlorination reaction.