کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
64886 | 48373 | 2015 | 9 صفحه PDF | دانلود رایگان |
• Tris-ureas and thiourea are explored towards catalytic Michael addition reactions.
• They efficiently catalyze the addition reaction of β-nitro styrenes and nucleophiles.
• Pentafluorophenyl attached tris-urea is found to be the most effective catalyst.
• The added advantage of bridge-head nitrogen center has been established.
• A plausible reaction mechanism has also been established.
Tris(2-aminoethyl)-amine, TREN based tris-ureas (1a–1d) and tris-thiourea (1e) have been explored towards a wide range of catalytic Michael addition reactions. These tris-ureas, 1a–1d efficiently catalyze the addition reaction of β-nitro styrenes (2a–2d) with various nucleophiles such as β-ketoesters (3a–3c), 1,3-dicarbonyl compound (3d), a cyanoester (3e) and a nitroester (3f) under ambient conditions to produce corresponding nitro alkanes in high yields. Pentafluorophenyl attached tris-urea, 1d is found to be the most effective catalyst in the series that yields 78–98% products conversion. In case of the reaction between β-nitro styrenes and malononitrile (3g) in presence of 1d, 2-amino-5-nitro-4,6-diphenylcyclohex-1-ene-1,3,3-tricarbonitriles are also isolated as a minor product along with the corresponding Michael adduct. The added advantage of bridge-head nitrogen center in tris-urea organocatalysts, 1a–1d has been established by studying analogous benzene platform based tris-ureas (1f, 1g, 1h) in similar experimental conditions. Furthermore, a plausible reaction mechanism has also been established based on in-situ 1H NMR kinetic studies.
Figure optionsDownload high-quality image (95 K)Download as PowerPoint slide
Journal: Journal of Molecular Catalysis A: Chemical - Volume 408, November 2015, Pages 287–295