- Base-promoted ring expansion of 3-aminopyrimidine-2-thiones into 1,2,4-triazepine-3-thiones
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A base-promoted ring expansion of 3-amino-4-hydroxyhexahydropyrimidine-2-thiones into 2,4,5,6-tetrahydro-3H-1,2,4-triazepine-3-thiones has been developed. Experimental data and DFT calculations showed that the reaction proceeded through fast formation of intermediate acyclic isomers of pyrimidines followed by their slow cyclization into triazepines. The starting hydroxypyrimidines were prepared by reaction of α,β-unsaturated ketones or β-alkoxy ketones with HNCS followed by treatment of the obtained β-isothiocyanato ketones with hydrazine. Triazepine-3-thiones were transformed into their 3-oxo analogs by oxidation with H2O2 under basic conditions.
- Fesenko, Anastasia A.,Shutalev, Anatoly D.
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supporting information
p. 2560 - 2573
(2016/04/26)
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- Lewis acid mediated selective chalcogenalkylation of silyl enol ethers with [O,S]-acetals
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Silyl enol ethers of ketones were selectively alkylated with [O,S]- acetals mediated by Lewis acid in a Mukaiyama type Aldol reaction. The products were β-alkoxy- and/or β-sulfanyl carbonyl compounds depending on the catalyst employed.
- Braga, Antonio L.,Dornelles, Luciano,Silveira, Claudio C.,Wessjohann, Ludger A.
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p. 562 - 564
(2007/10/03)
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- Reaction of Enamines with Acetals or Trialkyl Orthoformates Activated by Lewis Acids
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Enamines, prepared readily from various carbonyl compounds, react with acetals or trialkyl orthoformates in the presence of Lewis acids such as BF3.OEt2 to give corresponding β-alkoxy carbonyl compounds or α-dialkoxymethyl carbonyl compounds in good yields.The reaction of dienamines with acetals or trialkyl orthoformates also selectively gives corresponding β,χ-unsaturated α-(α-alkoxyalkyl) carbonyl compounds or β,χ-unsatureted α-dialkoxymethyl carbonyl compounds in good yields.
- Takazawa, Osamu,Kogami, Kunio,Hayashi, Kazuo
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p. 1876 - 1881
(2007/10/02)
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- CHEMISTRY OF ENOL ETHERS. LXVIII. SILYL ENOL ETHERS IN A MODIFIED ALDOL-CROTONIC CONDENSATION. PRODUCTION OF α,β-UNSATURATED KETONES
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By the condensation of the acetals of acetaldehyde, butyraldehyde, isobutyraldehyde, and acetone with the trimethylsilyl ethers of the enolic forms of cyclohexanone, cyclopentanone, and acetone in the presence of zinc chloride as catalyst and subsequent treatment of the reaction products with dilute hydrochloric acid the following α,β-unsaturated ketones were obtained: Ethylidene-, butylidene-, and isobutylidenecyclohexanones, the corresponding cyclopentanones, and methyl propenyl ketone.
- Makin, S. M.,Kruglikova, R. I.,Tagirov, T. K.,Kharitonova, O. V.
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p. 1075 - 1078
(2007/10/02)
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